PIK3CA gene encoding a catalytic subunit of the phosphatidylinositol-3-kinase (PI3K) is mutated and/or amplified in various neoplasia, including lung cancer. Here we investigated PIK3CA gene alterations, the expression of core components of PI3K pathway, and evaluated their clinical importance in non-small cell lung cancer (NSCLC).
Materials and methods
Oncogenic mutations/rearrangements in PIK3CA, EGFR, KRAS, HER2, BRAF, AKT1 and ALK genes were detected in tumors from 1117 patients with NSCLC. PIK3CA gene copy number was examined by fluorescent in situ hybridization and the expression of PI3K p110 subunit alpha (PI3K p110α), p-Akt, mTOR, PTEN was determined by immunohistochemistry in PIK3CA mutant cases and 108 patients without PIK3CA mutation.
PIK3CA mutation was found in 3.9% of squamous cell carcinoma and 2.7% of adenocarcinoma. Among 34 PIK3CA mutant cases, 17 tumors harbored concurrent EGFR mutations and 4 had KRAS mutations. PIK3CA mutation was significantly associated with high expression of PI3K p110α (p<0.0001), p-Akt (p = 0.024) and mTOR (p = 0.001), but not correlated with PIK3CA amplification (p = 0.463). Patients with single PIK3CA mutation had shorter overall survival than those with PIK3CA-EGFR/KRAS co-mutation or wildtype PIK3CA (p = 0.004). A significantly worse survival was also found in patients with PIK3CA mutations than those without PIK3CA mutations in the EGFR/KRAS wildtype subgroup (p = 0.043)
PIK3CA mutations frequently coexist with EGFR/KRAS mutations. The poor prognosis of patients with single PIK3CA mutation in NSCLC and the prognostic value of PIK3CA mutation in EGFR/KRAS wildtype subgroup suggest the distinct mutation status of PIK3CA gene should be determined for individual therapeutic strategies in NSCLC.
Deregulation of EGFR signaling is common in non-small cell lung cancers (NSCLC) and this finding led to the development of tyrosine kinase inhibitors (TKIs) that are highly effective in a subset of NSCLC. Mutations of EGFR (mEGFR) and copy number gains (CNGs) of EGFR (gEGFR) and HER2 (gHER2) have been reported to predict for TKI response. Mutations in KRAS (mKRAS) are associated with primary resistance to TKIs.
We investigated the relationship between mutations, CNGs and response to TKIs in a large panel of NSCLC cell lines. Genes studied were EGFR, HER2, HER3 HER4, KRAS, BRAF and PIK3CA. Mutations were detected by sequencing, while CNGs were determined by quantitative PCR (qPCR), fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (aCGH). IC50 values for the TKIs gefitinib (Iressa) and erlotinib (Tarceva) were determined by MTS assay. For any of the seven genes tested, mutations (39/77, 50.6%), copy number gains (50/77, 64.9%) or either (65/77, 84.4%) were frequent in NSCLC lines. Mutations of EGFR (13%) and KRAS (24.7%) were frequent, while they were less frequent for the other genes. The three techniques for determining CNG were well correlated, and qPCR data were used for further analyses. CNGs were relatively frequent for EGFR and KRAS in adenocarcinomas. While mutations were largely mutually exclusive, CNGs were not. EGFR and KRAS mutant lines frequently demonstrated mutant allele specific imbalance i.e. the mutant form was usually in great excess compared to the wild type form. On a molar basis, sensitivity to gefitinib and erlotinib were highly correlated. Multivariate analyses led to the following results:
1. mEGFR and gEGFR and gHER2 were independent factors related to gefitinib sensitivity, in descending order of importance.
2. mKRAS was associated with increased in vitro resistance to gefitinib.
Our in vitro studies confirm and extend clinical observations and demonstrate the relative importance of both EGFR mutations and CNGs and HER2 CNGs in the sensitivity to TKIs.
Genomic testing to identify driver mutations that enable targeted therapy is emerging for patients with non-small cell lung cancer (NSCLC). We report the implementation of systematic prospective genotyping for somatic alterations in BRAF, PIK3CA, HER2, and ALK, in addition to EGFR and KRAS, in NSCLC patients at the Dana-Farber Cancer Institute.
Patients with NSCLC were prospectively referred by their providers for clinical genotyping. Formalin-fixed, paraffin embedded tumor samples were analyzed by Sanger sequencing for mutations in selected exons of EGFR, KRAS, BRAF, PIK3CA, and HER2. ALK rearrangements were detected by FISH or immunohistochemistry.
Between 7/1/2009 and 8/1/2010, 427 specimens from 419 patients were referred for genomic characterization; 344 (81%) specimens were successfully genotyped with a median turnaround time of 31 days (range, 9-155). Of the 344 specimens, 185 (54%) had at least one identifiable somatic alteration (KRAS: 24%, EGFR: 17%, ALK: 5%, BRAF: 5%, HER2: 4%, PIK3CA: 2%). As of 8/1/2011, 63/288 (22%) advanced NSCLC patients had received molecularly targeted therapy based on their genotypic results, including 34/42 (81%) patients with EGFR mutations, 12/15 (80%) with ALK rearrangements, and 17/95 (18%) with KRAS, BRAF or HER2 mutations.
Large scale testing for somatic alterations in EGFR, KRAS, BRAF, PIK3CA, HER2 and ALK is feasible and impacts therapeutic decisions. As the repertoire for personalized therapies expands in lung cancer and other malignancies, there is a need to develop new genomics technologies that can generate a comprehensive genetic profile of tumor specimens in a time and cost effective manner.
Lung cancer; cancer genomics; molecular targeted therapy
Activating mutations in one allele of an oncogene (heterozygous mutations) are widely believed to be sufficient for tumorigenesis. However, mutant allele specific imbalance (MASI) has been observed in tumors and cell lines harboring mutations of oncogenes.
We determined 1) mutational status, 2) copy number gains (CNGs) and 3) relative ratio between mutant and wild type alleles of KRAS, BRAF, PIK3CA and EGFR genes by direct sequencing and quantitative PCR assay in over 400 human tumors, cell lines, and xenografts of lung, colorectal, and pancreatic cancers. Examination of a public database indicated that homozygous mutations of five oncogenes were frequent (20%) in 833 cell lines of 12 tumor types. Our data indicated two major forms of MASI: 1) MASI with CNG, either complete or partial; and 2) MASI without CNG (uniparental disomy; UPD), due to complete loss of wild type allele. MASI was a frequent event in mutant EGFR (75%) and was due mainly to CNGs, while MASI, also frequent in mutant KRAS (58%), was mainly due to UPD. Mutant: wild type allelic ratios at the genomic level were precisely maintained after transcription. KRAS mutations or CNGs were significantly associated with increased ras GTPase activity, as measured by ELISA, and the two molecular changes were synergistic. Of 237 lung adenocarcinoma tumors, the small number with both KRAS mutation and CNG were associated with shortened survival.
MASI is frequently present in mutant EGFR and KRAS tumor cells, and is associated with increased mutant allele transcription and gene activity. The frequent finding of mutations, CNGs and MASI occurring together in tumor cells indicates that these three genetic alterations, acting together, may have a greater role in the development or maintenance of the malignant phenotype than any individual alteration.
We performed this analysis to improve the understanding of the clinicopathological characteristics and clinical outcome of non-small cell lung cancer (NSCLC) patients harboring the primary epidermal growth factor receptor (EGFR) T790M mutation along with activating EGFR mutation.
Resected tumors from 1903 NSCLC patients were analyzed for mutation in EGFR, as well as KRAS (Kirsten rat sarcoma viral oncogene homolog), BRAF (v-raf murine sarcoma viral oncogene homolog B), HER2 (human epidermal growth factor 2), PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha), and EML4 (echinoderm microtubule associated protein like 4)–ALK (anaplastic lymphoma receptor tyrosine kinase) fusion. Fluorescence in situ hybridization was performed to define EGFR and c-MET (met proto-oncogene gene amplification. Expression of PIK3CA and p-Akt (phosphorylated protein kinase B) were tested using immunohistochemistry. Clinical and pathological data, including sex, age at diagnosis, stage, tumor differentiation, smoking history, histological subtype, relapse-free and overall survival, were further analyzed.
In all, 16 NSCLC patients were found to harbor primary EGFR T790M mutation, including 14 adenocarcinomas and two adenosquamous carcinomas, accounting for 2.04% of all the EGFR mutant cases and 0.84% of the total. No c-MET amplification was found to coexist with primary EGFR T790M. Fewer EGFR copy-number variations were found in samples harboring EGFR T790M mutations compared with those in patients with exon 19 deletions and L858R. Overall survival was significantly shorter for patients harboring EGFR T790M mutation than it was for patients with exon 19 deletions (logrank P=0.008). When taking patients harboring EGFR L858R or exon 19 deletions as one group, the overall survival was also significantly longer than that in patients with T790M mutation (logrank P=0.012). There was no significant difference in relapse-free survival among three subgroups of patients.
Our study described the clinicopathological and molecular characteristics of NSCLC patients harboring primary EGFR T790M mutations. Its value of being a predictor for worse prognosis was established. Primary EGFR T790M mutation is a rare event in NSCLC cases, but the therapeutic strategies for this subtype of patients should be precisely considered.
driver mutation; survival; clinicopathological profile; EGFR tyrosine kinase inhibitor; acquired resistance
Deregulation of the EGFR signaling pathway is one of the most frequently observed genetic abnormalities that drives cancer development. Although mutations in the downstream components of the EGFR signaling pathway, including KRAS, BRAF and PIK3CA, have been reported in numerous cancers, extensive mutation and copy number analysis of these genes in clinical samples has not been performed for head and neck squamous cell carcinoma (HNSCC).
We examined the mutations and copy number alterations of KRAS, BRAF and PIK3CA in 115 clinical specimens of HNSCC obtained from surgically treated patients.
We used DNA sequencing to detect mutations and the copy number changes were evaluated by qPCR and array comparative genomic hybridization (CGH) analysis.
We examined the mutations and copy number alterations of KRAS, BRAF and PIK3CA in 115 clinical specimens of HNSCC obtained from surgically treated patients. We identified 3 mutations (2.6%) in K-RAS and 3 mutations (2.6%) in PIK3CA. Copy number amplification was found in 37 cases (32.2%) for PIK3CA, 10 cases (8.7%) for K-RAS and 2 cases (1.7%) for BRAF. Kaplan-Meier survival analysis revealed that copy-number amplification of PIK3CA was markedly associated with cancer relapse in patients without lymph node metastasis. (Log-rank test, p = 0.026)
Copy number amplification of the PIK3CA gene is associated with poor prognosis in HNSCC patients without lymph node metastasis. The PIK3CA copy number status will serve as a marker of poor prognosis in patients with HNSCC.
PIK3CA; KRAS; BRAF; Copy number analysis; Prognostic Factor
Fifty percent of lung adenocarcinomas harbor somatic mutations in six genes that encode proteins in the EGFR signaling pathway, i.e., EGFR, HER2/ERBB2, HER4/ERBB4, PIK3CA, BRAF, and KRAS. We performed mutational profiling of a large cohort of lung adenocarcinomas to uncover other potential somatic mutations in genes of this signaling pathway that could contribute to lung tumorigenesis.
We analyzed genomic DNA from a total of 261 resected, clinically annotated non-small cell lung cancer (NSCLC) specimens. The coding sequences of 39 genes were screened for somatic mutations via high-throughput dideoxynucleotide sequencing of PCR-amplified gene products. Mutations were considered to be somatic only if they were found in an independent tumor-derived PCR product but not in matched normal tissue. Sequencing of 9MB of tumor sequence identified 239 putative genetic variants. We further examined 22 variants found in RAS family genes and 135 variants localized to exons encoding the kinase domain of respective proteins. We identified a total of 37 non-synonymous somatic mutations; 36 were found collectively in EGFR, KRAS, BRAF, and PIK3CA. One somatic mutation was a previously unreported mutation in the kinase domain (exon 16) of FGFR4 (Glu681Lys), identified in 1 of 158 tumors. The FGFR4 mutation is analogous to a reported tumor-specific somatic mutation in ERBB2 and is located in the same exon as a previously reported kinase domain mutation in FGFR4 (Pro712Thr) in a lung adenocarcinoma cell line.
This study is one of the first comprehensive mutational analyses of major genes in a specific signaling pathway in a sizeable cohort of lung adenocarcinomas. Our results suggest the majority of gain-of-function mutations within kinase genes in the EGFR signaling pathway have already been identified. Our findings also implicate FGFR4 in the pathogenesis of a subset of lung adenocarcinomas.
Meta-analyses were conducted to characterize patterns of mutation incidence in non small-cell lung cancer (NSCLC).
Nine genes with the most complete published mutation coincidence data were evaluated. One meta-analysis generated a ‘mutMap’ to visually represent mutation coincidence by ethnicity (Western/Asian) and histology (adenocarcinoma [ADC] or squamous cell carcinoma). Another meta-analysis evaluated incidence of individual mutations. Extended analyses explored incidence of EGFR and KRAS mutations by ethnicity, histology, and smoking status.
Genes evaluated were TP53, EGFR, KRAS, LKB1, EML4-ALK, PTEN, BRAF, PIK3CA, and ErbB2. The mutMap highlighted mutation coincidences occurring in ≥5% of patients, including TP53 with KRAS or EGFR mutations in patients with ADC, and TP53 with LKB1 mutation in Western patients. TP53 was the most frequently mutated gene overall. Frequencies of TP53, EGFR, KRAS, LKB1, PTEN, and BRAF mutations were influenced by histology and/or ethnicity. Although EGFR mutations were most frequent in patients with ADC and never/light smokers from Asia, and KRAS mutations were most frequent in patients with ADC and ever/heavy smokers from Western countries, both were detected outside these subgroups.
Potential molecular pathology segments of NSCLC were identified. Further studies of mutations in NSCLC are warranted to facilitate more specific diagnoses and guide treatment.
geography; histology; lung cancer; mutation coincidence; oncogenes
Phosphatidylinositol-3-kinase (PI3K) activation involves the epidermal growth factor receptor (EGFR) and plays an important role in cell survival signaling in pancreaticobiliary cancer. EGFR gene mutations have been correlated with clinical response to EGFR inhibitors in patients with advanced non-small cell lung cancer. This study examined the prevalence of PIK3CA and EGFR mutations in pancreaticobiliary cancer where erlotinib, an EGFR inhibitor, is approved for therapy.
Thirty patients who underwent pancreatectomy for pancreaticobiliary carcinoma were identified. Genomic DNA was extracted from formalin fixed paraffin embedded tumor and adjacent normal tissue, and exons 9 and 20 (for the PIK3CA gene) and exons 18-21 (for the EGFR gene) were amplified by PCR and sequenced. Literature review on EGFR and/or PIK3CA mutations in pancreaticobiliary adenocarcinomas was conducted.
No mutations in either PIK3CA or EGFR genes were identified. The study identified one synonymous single nucleotide polymorphism (SNP) (rs1050171) in the coding region of EGFR. A previously unreported change, suspected to be a SNP, was observed in intron 18 of EGFR (IVS18+15, C>T). Review of the literature showed EGFR mutation rate of 2% and 10.5% in pancreatic and biliary tract carcinomas, respectively. PIK3CA mutations were found in 3.6% and 11.7% of pancreatic and biliary tract carcinomas, respectively.
A low prevalence of EGFR or PIK3CA mutations exists in pancreatic cancer (<5%), indicating that mutation screening may not be as useful in determining prognosis or response to targeted inhibition.
Phosphatidylinositol-3-kinase catalytic subunit (PIK3CA); epidermal growth factor receptor (EGFR); mutations; pancreas; biliary; cancer
Preclinical studies in non-small cell lung cancer (NSCLC) suggest the interaction of PTEN and PI3K affects sensitivity to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). We investigated outcomes in relation to PTEN, PIK3CA and EGFR gene copy number, and chromosome 7 (CEN7) polysomy in NSCLC patients treated with gefitinib.
Fluorescent in situ hybridisation analyses of PTEN, PIK3CA, EGFR and CEN7 were performed on tumour specimens from patients treated on the expanded access gefitinib trial. Progression-free survival (PFS) and overall survival (OS) were correlated with outcomes in all patients and EGFR wild-type patients.
Progression-free survival (hazard ratio=2.54, P<0.001) and OS (hazard ratio=4.04, P<0.001) were significantly shorter in patients whose tumours had all of the following molecular patterns: CEN7 <4 copies per cell, PTEN loss (<2 copies in at least 20% of cells), and PIK3CA gain (>2 copies in at least 40% of cells) both in all and EGFR wild-type only patients.
The combination of low CEN7 copy number, PTEN loss, and PI3KCA gain may be useful for identifying NSCLC patients unlikely to benefit from treatment with EGFR (TKIs), specifically in wild-type EGFR cases.
EGFR; PTEN; PI3KCA; lung cancer; gefitinib
The employment of anti-epidermal growth factor receptor (EGFR) antibodies represents a backbone of the therapeutic options for the treatment of metastatic colorectal cancer (mCRC). However, this therapy is poorly effective or ineffective in unselected patients. Mutations in KRAS, BRAF and PIK3CA genes have recently emerged as the best predictive factors of low/absent response to EGFR-targeted therapy. Due to the need for efficacious treatment options for mCRC patients bearing these mutations, in this short report we examined the antitumoral activity of the protease inhibitor gabexate mesilate, alone and in combination with the anti-EGFR monoclonal antibody cetuximab, in a panel of human CRC cell lines harbouring a different expression pattern of wild-type/mutated KRAS, BRAF and PIK3CA genes. Results obtained showed that gabexate mesilate significantly inhibited the growth, invasive potential and tumour-induced angiogenesis in all the CRC cells employed in this study (including those ones harbouring dual KRAS/PIK3CA or BRAF/PIK3CA mutation), while cetuximab affected these parameters only in CRC cells with KRAS, BRAF and PIK3CA wild-type. Notably, the antitumoral efficacy of gabexate mesilate and cetuximab in combination was found to be not superior than that observed with gabexate mesilate as single agent. Overall, these preliminary findings suggest that gabexate mesilate could represent a promising therapeutic option for mCRC patients, particularly for those harbouring KRAS, BRAF and PIK3CA mutations, either as mono-therapy or in addition to standard chemotherapy regimens. Further studies to better elucidate gabexate mesilate mechanism of action in CRC cells are therefore warranted.
Individual therapy based on various pathohistological types and biological characteristics may be the practical trend of advanced non-small cell lung cancer (NSCLC) treatment. To provide a molecular criterion for drug selection, we investigated the incidence of somatic mutation and mRNA expression levels of common genes relevant to treatment response in a population with locally advanced NSCLC. Mutant-enriched and branched DNA-liquidchip technology (bDNA-LCT) were used to detect the somatic mutations in the epidermal growth factor receptor (EGFR), KRAS, BRAF and phosphatidylinositol-3-kinase catalytic α (PIK3CA) genes, and mRNA levels of EGFR, ERCC1, class III β-tubulin (TUBB3) and TYMS, separately, in paraffin tissue blocks from 30 patients with stage IIIA NSCLC. Our current findings revealed that 6, 4 and 2 out of 30 samples were found with mutations in exons 19, 21 and 20 of the EGFR gene, respectively. The mutation incidence of exons 19 and 21 had a positive correlation with EGFR mRNA expression. Mutations in exons 12 and 13 of the K-ras gene were found in 2 out of 30, and 1 out of 30 samples, separately. Three out of 30 samples were found with mutations in codon 542 of the PIK3CA gene. No mutations were found in the BRAF gene. The expression levels of ERCC1 and TUBB3 mRNAs were higher in patients with adenocarcinoma than those in patients with squamous cell carcinoma. The expression of TYMS mRNA in patients with adenocarcinoma was lower than that in patients with squamous cell carcinoma. In conclusion, mutations and mRNA expression of these commonly studied genes provides a basis for the selection of suitable molecular markers for individual treatment in a population with locally advanced NSCLC.
gene mutation; expression; treatment response related genes; locally advanced non-small cell lung cancer
There is much accumulated evidence that EGFR, HER2, and their downstream signaling pathway members such as KRAS, BRAF, and PIK3CA are strongly implicated in cancer development and progression. Recently, mutations in the kinase domains of EGFR and HER2, associated with increased sensitivity to tyrosine kinase inhibitors, have been described.
To evaluate the mutational status of these genes in intraductal papillary mucinous neoplasm (IPMN)/intraductal papillary mucinous carcinoma (IPMC), EGFR and HER2 were analyzed in 36 IPMN/IPMC, and the results were correlated to the mutational status of the KRAS, BRAF, and PIK3CA genes in the samples.
Together, we identified 1 silent mutation of HER2, 17 (43%) KRAS mutations, 1 (2.7%) BRAF mutation, and 4 (11%) mutations of PIK3CA in the IPMN/IPMC samples.
The EGFR and ERBB2 (HER2) mutations are very infrequent in IPMN/IPMC, suggesting the limited possibility of targeting mutated ERBB2 and EGFR for therapy for these lesions. The KRAS, BRAF, and PIK3CA, however, could represent interesting targets for future therapies in these lesions.
Her2; EGFR; PIK3CA; KRAS; BRAF; IPMN
Anti-EGFR therapy appears to be a potential treatment option for squamous cell anal carcinoma (SCAC). KRAS mutation is a rare event in SCAC, indicating the absence of the principal mechanism of resistance to this type of therapy. However, no information is available from the literature regarding the status of BRAF or PIK3CA in this cancer type. We analysed KRAS, BRAF and PIK3CA status in SCAC patients in relation to the clinical-pathological characteristics of patients and to the presence of the human papilloma virus (HPV). One hundred and three patients were treated with the Nigro scheme for anal cancer from March 2001 to August 2012. Fifty patients were considered for the study as there was insufficient paraffin-embedded tumour tissue to perform molecular analysis the remaining 53. DNA was extracted from paraffin-embedded sections. KRAS, BRAF and PIK3CA gene status and HPV genotype were evaluated by pyrosequencing. KRAS and BRAF genes were wild-type in all cases. Conversely, PIK3CA gene was found to be mutated in 11 (22%) cases. In particular, 8 mutations occurred in exon 9 and 3 in exon 20 of the PIK3CA gene. These findings suggest that SCAC could potentially respond to an anti-EGFR drug. PIK3CA mutation may be involved in the process of carcinogenesis in some cases of SCAC.
PIK3CA encodes the p110α subunit of the mitogenic signaling protein phosphatidylinositol 3-kinase (PI3K). PIK3CA mutations in the helical binding domain and the catalytic subunit of the protein have been associated with tumorigenesis and treatment resistance in various malignancies. Characteristics of patients with PIK3CA-mutant lung adenocarcinomas have not been reported.
We examined EGFR, KRAS, BRAF, HER2, PIK3CA, AKT1, NRAS, MEK1, and ALK in patients with adenocarcinoma of the lung to identify driver mutations. Clinical data were obtained from the medical records of individuals with mutations in PIK3CA.
Twenty-three of 1125 (2%, 95% confidence interval (CI) 1–3%) patients had a mutation in PIK3CA, 12 in Exon 9 (10 E545K, 2 E542K) and 11 in Exon 20 (3 H1047L, 8 H1047R). The patients (57% women) had a median age of 66 at diagnosis (range 34–78). Eight patients (35%) were never smokers. Sixteen of 23 (70%, 95% CI 49 – 86%) had coexisting mutations in other oncogenes - 10 KRAS, 1 MEK1, 1 BRAF, 1 ALK rearrangement, and 3 EGFR exon 19 deletions.
We conclude that PIK3CA mutations occur in lung adenocarcinomas, usually concurrently with EGFR, KRAS, and ALK. The impact of PIK3CA mutations on the efficacy of targeted therapies such as erlotinib and crizotinib is unknown. Given the high frequency of overlapping mutations, comprehensive genotyping should be performed on tumor specimens from patients enrolling on clinical trials of PI3K and other targeted therapies.
lung adenocarcinoma; oncogene; PIK3CA
The iterative discovery in various malignancies during the past decades that a number of aberrant tumorigenic processes and signal transduction pathways are mediated by “druggable” protein kinases has led to a revolutionary change in drug development. In non-small cell lung cancer (NSCLC), the ErbB family of receptors (e.g., EGFR [epidermal growth factor receptor], HER2 [human epidermal growth factor receptor 2]), RAS (rat sarcoma gene), BRAF (v-raf murine sarcoma viral oncogene homolog B1), MAPK (mitogen-activated protein kinase) c-MET (c-mesenchymal-epithelial transition), FGFR (fibroblast growth factor receptor), DDR2 (discoidin domain receptor 2), PIK3CA (phosphatidylinositol-4,5-bisphosphate3-kinase, catalytic subunit alpha)), PTEN (phosphatase and tensin homolog), AKT (protein kinase B), ALK (anaplastic lym phoma kinase), RET (rearranged during transfection), ROS1 (reactive oxygen species 1) and EPH (erythropoietin-producing hepatoma) are key targets of various agents currently in clinical development. These oncogenic targets exert their selective growth advantage through various intercommunicating pathways, such as through RAS/RAF/MEK, phosphoinositide 3-kinase/AKT/mammalian target of rapamycin and SRC-signal transduction and transcription signaling. The recent clinical studies, EGFR tyrosine kinase inhibitors and crizotinib were considered as strongly effective targeted therapies in metastatic NSCLC. Currently, five molecular targeted agents were approved for treatment of advanced NSCLC: Gefitinib, erlotinib and afatinib for positive EGFR mutation, crizotinib for positive echinoderm microtubule-associated protein-like 4 (EML4)-ALK translocation and bevacizumab. Moreover, oncogenic mutant proteins are subject to regulation by protein trafficking pathways, specifically through the heat shock protein 90 system. Drug combinations affecting various nodes in these signaling and intracellular processes are predicted and demonstrated to be synergistic and advantageous in overcoming treatment resistance compared with monotherapy approaches. Understanding the role of the tumor microenvironment in the development and maintenance of the malignant phenotype provided additional therapeutic approaches as well. More recently, improved knowledge on tumor immunology has set the stage for promising immunotherapies in NSCLC. This review will focus on the rationale for the development of targeted therapies in NSCLC and the various strategies employed in preventing or overcoming the inevitable occurrence of treatment resistance.
Drug resistance; heat shock protein 90 inhibitors; non-small cell lung cancer; programmed cell death-1 receptor inhibitors; protein kinase inhibitors
Phosphatidylinositol 3-kinases (PI3Ks) are a group of lipid kinases that regulate signaling pathways involved in cell proliferation, adhesion, survival, and motility. Even though PIK3CA amplification and somatic mutation have been reported previously in various kinds of human cancers, the genetic change in PIK3CA in human breast cancer has not been clearly identified.
Fifteen breast cancer cell lines and 92 primary breast tumors (33 with matched normal tissue) were used to check somatic mutation and gene copy number of PIK3CA. For the somatic mutation study, we specifically checked exons 1, 9, and 20, which have been reported to be hot spots in colon cancer. For the analysis of the gene copy number, we used quantitative real-time PCR and fluorescence in situ hybridization. We also treated several breast cancer cells with the PIK3CA inhibitor LY294002 and compared the apoptosis status in cells with and without PIK3CA mutation.
We identified a 20.6% (19 of 92) and 33.3% (5 of 15) PIK3CA somatic mutation frequency in primary breast tumors and cell lines, respectively. We also found that 8.7% (8 of 92) of the tumors harbored a gain of PIK3CA gene copy number. Only four cases in this study contained both an increase in the gene copy number and a somatic mutation. In addition, mutation of PIK3CA correlated with the status of Akt phosphorylation in some breast cancer cells and inhibition of PIK3CA-induced increased apoptosis in breast cancer cells with PIK3CA mutation.
Somatic mutation rather than a gain of gene copy number of PIK3CA is the frequent genetic alteration that contributes to human breast cancer progression. The frequent and clustered mutations within PIK3CA make it an attractive molecular marker for early detection and a promising therapeutic target in breast cancer.
Background and aims
Recent studies have reported high frequencies of somatic mutations in
the phosphoinositide-3-kinase catalytic-α (PIK3CA)
gene in various human tumors. Three hot-spot mutations in the exons 9 and 20
have been proven to activate the Akt signalling pathway. The Raf/MEK/ERK
(mitogen-activated protein kinase) signal transduction is an important
mediator of a number of cellular fates including growth, proliferation, and
survival. The BRAF gene is activated by oncogenic RAS, leading to
cooperative effects in cells responding to growth factor signals. Here we
evaluate the mutational status of PIK3CA, KRAS, and BRAF in intraductal
papillary mucinous neoplasm/carcinoma (IPMN/IPMNC) of the pancreas.
Materials and methods
Exons 1, 4, 5, 6, 7, 9, 12, 18, and 20 of PIK3CA,
exons 1 of KRAS, and exons 5, 11, and 15 of
BRAF were analyzed in 36 IPMN/IPMC and two mucinous
cystadenoma specimens by direct genomic DNA sequencing.
We identified four somatic missense mutations of PIK3CA within the 36
IPMN/IPMC specimens (11%). One of the four mutations, H1047R, has
been previously reported to be a hot-spot mutation. Furthermore, we found 17
(47%) KRAS mutations in exon 1 and one missense mutation
(2.7%) in exon 15 of BRAF.
This data is the first report of PIK3CA mutation in
pancreatic cancer and it appears to be the first oncogene to be mutated in
IPMN/IPMC but not in conventional ductal adenocarcinoma of the pancreas. Our
data provide evidence that PIK3CA and BRAF
contribute to the tumorigenesis of IPMN/IPMC, but at a lower frequency than
IPMN; IPMC; Pancreas; PIK3CA; KRAS; BRAF; Mutation
To develop gene expression profiles that characterise KRAS-, BRAF- or PIK3CA-activated- tumours, and to explore whether these profiles might be helpful in predicting the response to the epidermal growth factor receptor (EGFR) pathway inhibitors better than mutation status alone.
Fresh frozen tumour samples from 381 colorectal cancer (CRC) patients were collected and mutations in KRAS, BRAF and PIK3CA were assessed. Using microarray data, three individual oncogenic and a combined model were developed and validated in an independent set of 80 CRC patients, and in a dataset from metastatic CRC patients treated with cetuximab.
175 tumours (45.9%) harboured oncogenic mutations in KRAS (30.2%), BRAF (11.0%) and PIK3CA (11.5%). Activating mutation signatures for KRAS (75 genes), for BRAF (58 genes,) and for PIK3CA (49 genes) were developed. The development of a combined oncogenic pathway signature-classified tumours as ‘activated oncogenic’, or as ‘wildtype-like’ with a sensitivity of 90.3% and a specificity of 61.7%. The identified signature revealed other mechanisms that can activate ERK/MAPK pathway in KRAS, BRAF and PIK3CA wildtype patients. The combined signature is associated with response to cetuximab treatment in patients with metastatic CRC (HR 2.51, p<0.0009).
A combined oncogenic pathway signature allows the identification of patients with an active EGFR-signalling pathway that could benefit from downstream pathway inhibition.
Colorectal cancer; KRAS; BRAF; PIK3CA; EGFR-inhibitor resistance; cancer; colorectal metastases; drug resistance; gene expression; molecular oncology; colorectal neoplasia; cancer genetics; cancer syndromes; colorectal adenomas; pancreatic cancer
Bronchopulmonary neuroendocrine tumours (BP-NETs) comprise a large spectrum of tumours including typical carcinoids (TCs), atypical carcinoids (ACs), large-cell neuroendocrine carcinomas (LCNECs) and small-cell lung carcinomas (SCLCs) that exhibit considerably different biological aggressiveness and clinical behaviours. The phosphatidylinositol-3-kinase α catalytic subunit (PIK3CA) gene is known to be involved in the pathogenesis of several types of human cancers through gene amplification, deletions or somatic missense mutations within the helical and catalytic domains. However, the PIK3CA gene status in BP-NETs has yet to be explored. This study aimed to investigate the PIK3CA gene status in a large series of BP-NETs by direct gene sequencing and to analyse its correlation with the main clinicopathological parameters. To the best of our knowledge, we demonstrated for the first time a high frequency of somatic missense mutations (23.2%) in the PIK3CA gene in a series of 190 BP-NETs, including 75 TCs, 23 ACs, 17 LCNECs and 75 SCLCs. The frequency of the PIK3CA gene mutation in the kinase domain was higher (17.9%) than that in the helical domain (5.3%). When the mutational status of the PIK3CA gene was compared with the main clinical and pathological characteristics of the BP-NET patients, we found a significant association between PIK3CA gene mutations and BP-NET histology (P=0.011). Interestingly, the frequency of PIK3CA gene mutations increased with the biological aggressiveness of all BP-NETs, except LCNECs. In conclusion, our results suggest that PIK3CA gene mutations may play a key role in tumourigenesis and aggressiveness of BP-NETs. The PIK3CA gene may represent a favourable candidate for an effective therapeutic strategy in the treatment of patients with BP-NETs.
bronchopulmonary neuroendocrine tumours; PI3K/Akt/mTOR pathway; phosphatidylinositol-3-kinase α catalytic subunit mutations; biomarkers
Primary small cell carcinoma of the esophagus (PSCCE) is a rare and aggressive tumor with poor prognosis. The aim of this study was to investigate the existence of EGFR, KRAS, PIK3CA and PTEN mutations in PSCCE.
Clinical–pathological data and paraffin-embedded specimens were collected from 38 patients. Exons 18 to 21 of EGFR, KRAS and PIK3CA status were analyzed by real-time PCR based on ARMS and Scorpion technology in all patients, and the PTEN gene was also screened using real-time PCR and high-resolution melting curve analysis (HRMA).
Only 1 (2.63%) out of 38 patients had EGFR mutations in L858R missense, and KRAS and PIK3CA were not found in the mutational spot in all patients. However, PTEN mutations presented in 14 (36.84%) out of 38 patients, including exon 5 coding for PTEN missense mutation (n =4, 10.53%), exon 6 (n =7, 18.42%), concurrent exon 5 and exon 6 (n =2, 5.26%), and exon 8 (n =1, 2.63%). Concurrent mutations of these genes were not detected in all samples. No statistically significant associations were found between the clinicopathological features and the mutation status of PTEN.
The incidence of PTEN mutations in Chinese patients with PSCCE was higher than that of previous reports in other histological subtypes of esophageal cancer.
Primary small cell carcinoma of the esophagus; PTEN; EGFR; KRAS; PIK3CA; Mutation
Lung cancers harboring mutations in the epidermal growth factor receptor (EGFR) respond to EGFR tyrosine kinase inhibitors, but drug resistance invariably emerges. To elucidate mechanisms of acquired drug resistance, we performed systematic genetic and histological analyses of tumor biopsies from 37 patients with drug-resistant non–small cell lung cancers (NSCLCs) carrying EGFR mutations. All drug-resistant tumors retained their original activating EGFR mutations, and some acquired known mechanisms of resistance including the EGFR T790M mutation or MET gene amplification. Some resistant cancers showed unexpected genetic changes including EGFR amplification and mutations in the PIK3CA gene, whereas others underwent a pronounced epithelial-to-mesenchymal transition. Surprisingly, five resistant tumors (14%) transformed from NSCLC into small cell lung cancer (SCLC) and were sensitive to standard SCLC treatments. In three patients, serial biopsies revealed that genetic mechanisms of resistance were lost in the absence of the continued selective pressure of EGFR inhibitor treatment, and such cancers were sensitive to a second round of treatment with EGFR inhibitors. Collectively, these results deepen our understanding of resistance to EGFR inhibitors and underscore the importance of repeatedly assessing cancers throughout the course of the disease.
The development of oral squamous cell carcinoma (OSCC) is a complex, multistep process. To date, numerous oncogenes and tumor-suppressor genes have been implicated in oral carcinogenesis. Of particular interest in this regard are genes involved in cell cycling and apoptosis, such BRAF, KRAS, and PIK3CA genes.
Mutations of BRAF, KRAS, and PIK3CA were evaluated by direct genomic sequencing of exons 1 of KRAS, 11 and 15 of BRAF, and 9 and 20 of PIK3CA in OSCC specimens.
Both BRAF and KRAS mutations were detected with a mutation frequency of 2% (1/42). PIK3CA mutations were detected at 3% (1/35).
This is the first report implicating BRAF mutation in OSCC. Our study supports that mutations in the BRAF, KRAS, and PIK3CA genes make at least a minor contribution to OSCC tumorigenesis, and pathway-specific therapies targeting these two pathways should be considered for OSCC in a subset of patients with these mutations.
BRAF; KRAS; PIK3CA; oncogene mutation; hot-spot mutation; oral squamous cell carcinoma; OSCC
Mutations in KRAS oncogene are recognized biomarkers that predict lack of response to anti- epidermal growth factor receptor (EGFR) antibody therapies. However, some patients with KRAS wild-type tumors still do not respond, so other downstream mutations in BRAF, PIK3CA and NRAS should be investigated. Herein we used direct sequencing to analyze mutation status for 676 patients in KRAS (codons 12, 13 and 61), BRAF (exon 11 and exon 15), PIK3CA (exon 9 and exon 20) and NRAS (codons12, 13 and 61). Clinicopathological characteristics associations were analyzed together with overall survival (OS) of metastatic colorectal cancer patients (mCRC). We found 35.9% (242/674) tumors harbored a KRAS mutation, 6.96% (47/675) harbored a BRAF mutation, 9.9% (62/625) harbored a PIK3CA mutation and 4.19% (26/621) harbored a NRAS mutation. KRAS mutation coexisted with BRAF, PIK3CA and NRAS mutation, PIK3CA exon9 mutation appeared more frequently in KRAS mutant tumors (P = 0.027) while NRAS mutation almost existed in KRAS wild-types (P<0.001). Female patients and older group harbored a higher KRAS mutation (P = 0.018 and P = 0.031, respectively); BRAF (V600E) mutation showed a higher frequency in colon cancer and poor differentiation tumors (P = 0.020 and P = 0.030, respectively); proximal tumors appeared a higher PIK3CA mutation (P<0.001) and distant metastatic tumors shared a higher NRAS mutation (P = 0.010). However, in this study no significant result was found between OS and gene mutation in mCRC group. To our knowledge, the first large-scale retrospective study on comprehensive genetic profile which associated with anti-EGFR MoAbs treatment selection in East Asian CRC population, appeared a specific genotype distribution picture, and the results provided a better understanding between clinicopathological characteristics and gene mutations in CRC patients.
As supplement to KRAS mutational analysis, BRAF and PIK3CA mutations as well as expression of PTEN may account for additional non-responders to anti-EGFR-MoAbs treatment. The aim of the present study was to investigate the utility as biomarkers of these mutations in a uniform cohort of patients with metastatic colorectal cancer treated with third-line cetuximab/irinotecan.
One-hundred-and-seven patients were prospectively included in the study. Mutational analyses of KRAS, BRAF and PIK3CA were performed on DNA from confirmed malignant tissue using commercially available kits. Loss of PTEN and EGFR was assessed by immunohistochemistry.
DNA was available in 94 patients. The frequency of KRAS, BRAF and PIK3CA mutations were 44%, 3% and 14%, respectively. All were non-responders. EGF receptor status by IHC and loss of PTEN failed to show any clinical importance. KRAS and BRAF were mutually exclusive. Supplementing KRAS analysis with BRAF and PIK3CA indentified additional 11% of non-responders. Patient with any mutation had a high risk of early progression, whereas triple-negative status implied a response rate (RR) of 41% (p < 0.001), a disease control (DC) rate of 73% (p < 001), and a significantly higher PFS of 7.7(5.1-8.6 95%CI) versus 2.3 months (2.1-3.695%CI) (p < 0.000).
Triple-negative status implied a clear benefit from treatment, and we suggest that patient selection for third-line combination therapy with cetuximab/irinotecan could be based on triple mutational testing.
metastatic colorectal cancer; KRAS; BRAF; PIK3CA/PTEN mutations; Cetuximab and Irinotecan