BRAF mutations occur in 10–15% of colorectal cancers (CRCs) and confer adverse outcome. While RAF inhibitors such as vemurafenib (PLX4032) have proven effective in BRAF mutant melanoma, they are surprisingly ineffective in BRAF mutant CRCs, and the reason for this disparity remains unclear. Compared to BRAF mutant melanoma cells, BRAF mutant CRC cells were less sensitive to vemurafenib, and P-ERK suppression was not sustained in response to treatment. Although transient inhibition of phospho-ERK by vemurafenib was observed in CRC, rapid ERK re-activation occurred through EGFR-mediated activation of RAS and CRAF. BRAF mutant CRCs expressed higher levels of phospho-EGFR than BRAF mutant melanomas, suggesting that CRCs are specifically poised for EGFR-mediated resistance. Combined RAF and EGFR inhibition blocked reactivation of MAPK signaling in BRAF mutant CRC cells and markedly improved efficacy in vitro and in vivo. These findings support evaluation of combined RAF and EGFR inhibition in BRAF mutant CRC patients.
BRAF; vemurafenib; EGFR; colorectal cancer; melanoma
Invasion and metastasis increase after inhibition of vascular endothelial growth factor (VEGF) signaling in some preclinical tumor models. The present study asked whether selective VEGF inhibition is sufficient to increase invasion and metastasis and whether selective c-Met inhibition is sufficient to block this effect. Treatment of pancreatic neuroendocrine tumors in RIP-Tag2 mice with a neutralizing anti-VEGF antibody reduced tumor burden but increased tumor hypoxia, HIF-1α, and c-Met activation, and also increased invasion and metastasis. However, invasion and metastasis were reduced by concurrent inhibition of c-Met by PF-04217903 or PF-02341066 (crizotinib). Similar benefit was found in orthotopic Panc-1 pancreatic carcinomas treated with sunitinib plus PF-04217903 and in RIP-Tag2 tumors treated with XL184 (cabozantinib), which simultaneously blocks VEGF and c-Met signaling. These findings document that invasion and metastasis are promoted by selective inhibition of VEGF signaling and can be reduced by concurrent inhibition of c-Met.
Evasive resistance; pancreatic cancer; angiogenesis inhibitors
The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) apoptotic pathway has emerged as a cancer therapeutic target. However, clinical trials have proven that the vast majority of human cancers are resistant to TRAIL-targeted therapies. We show here that A20-mediated ubiquitination inhibits caspase-8 cleavage and TRAIL-induced apoptosis in glioblastoma through two signaling complexes. A20 is highly expressed in glioblastomas and, together with the death receptor 5 (DR5) and receptor-interacting protein 1 (RIP1), forms a plasma membrane bound preligand assembly complex (PLAC) under physiologic conditions. TRAIL treatment leads to the recruitment of caspase-8 to the PLAC for the assembly of a death-inducing signaling complex (DISC). In the DISC, the C-terminal Zinc finger (Znf) domain of A20 ubiquitin ligase mediates RIP1 ubiquitination through lysine (K)-63-linked polyubiquitin chains that bind the protease domain of caspase-8 and inhibits its dimerization, cleavage and the initiation of TRAIL-induced apoptosis in glioblastoma-derived cell lines and tumor-initiating cells.
A20; apoptosis; caspase-8; TRAIL; ubiquitination
The transcription factor ZNF217 is a candidate oncogene in the amplicon on chromosome 20q13 that occurs in 20% to 30% of primary human breast cancers and that correlates with poor prognosis. We show that Znf217 overexpression drives aberrant differentiation and signaling events, promotes increased self-renewal capacity, mesenchymal marker expression, motility, and metastasis, and represses an adult tissue stem cell gene signature downregulated in cancers. By in silico screening, we identified candidate therapeutics that at low concentrations inhibit growth of cancer cells expressing high ZNF217. We show that the nucleoside analogue triciribine inhibits ZNF217-induced tumor growth and chemotherapy resistance and inhibits signaling events [e.g., phospho-AKT, phospho-mitogen-activated protein kinase (MAPK)] in vivo. Our data suggest that ZNF217 is a biomarker of poor prognosis and a therapeutic target in patients with breast cancer and that triciribine may be part of a personalized treatment strategy in patients overexpressing ZNF217. Because ZNF217 is amplified in numerous cancers, these results have implications for other cancers.
This study finds that ZNF217 is a poor prognostic indicator and therapeutic target in patients with breast cancer and may be a strong biomarker of triciribine treatment efficacy in patients. Because previous clinical trials for triciribine did not include biomarkers of treatment efficacy, this study provides a rationale for revisiting triciribine in the clinical setting as a therapy for patients with breast cancer who overexpress ZNF217.
Effective oncoprotein-targeted therapies have not yet been developed for ovarian cancer. To explore the role of PI3 kinase/AKT signaling in this disease, we performed a genetic and functional analysis of ovarian cancer cell lines and tumors. PI3K pathway alterations were common in both, but the spectrum of mutational changes differed. Genetic activation of the pathway was necessary, but not sufficient, to confer sensitivity to selective inhibition of AKT and cells with RAS pathway alterations or RB1 loss were resistant to AKT inhibition, whether or not they had coexistent PI3K/AKT pathway activation. Inhibition of AKT1 caused growth arrest in a subset of ovarian cell lines, but not in those with AKT3 expression, which required pan-AKT inhibition. Thus, a subset of ovarian tumors are sensitive to AKT inhibition, but the genetic heterogeneity of the disease suggests that effective treatment with AKT pathway inhibitors will require a detailed molecular analysis of each patient’s tumor.
Ovarian; AKT; MK2206; TCGA; PTEN
Knowledge of “actionable” somatic genomic alterations present in each tumor (e.g., point mutations, small insertions/deletions, and copy number alterations that direct therapeutic options) should facilitate individualized approaches to cancer treatment. However, clinical implementation of systematic genomic profiling has rarely been achieved beyond limited numbers of oncogene point mutations. To address this challenge, we utilized a targeted, massively parallel sequencing approach to detect tumor genomic alterations in formalin-fixed, paraffin embedded (FFPE) tumor samples. Nearly 400-fold mean sequence coverage was achieved, and single nucleotide sequence variants, small insertions/deletions, and chromosomal copy number alterations were detected simultaneously with high accuracy compared to other methods in clinical use. Putatively actionable genomic alterations, including those that predict sensitivity or resistance to established and experimental therapies, were detected in each tumor sample tested. Thus, targeted deep sequencing of clinical tumor material may enable mutation-driven clinical trials and, ultimately, ”personalized” cancer treatment.
The Mammary Prevention 3 (MAP.3) placebo-controlled randomized trial in 4,560 high-risk postmenopausal women showed a 65% reduction in invasive breast cancer with the use of exemestane at 35 months median follow-up. Few differences in adverse events were observed between the arms, suggesting a promising risk:benefit balance with exemestane for use in chemoprevention. Yet, the MAP.3 design and implementation raise concerns regarding limited data maturity and not prospectively including key bone-related and other toxicities as study end points. Exemestane for prevention is juxtaposed against selective estrogen receptor modulators and the other aromatase inhibitors. Additional issues for prevention, including the influence of obesity, alternative dosing, and biomarker use in phase III trials, are addressed.
The recently completed MAP.3 trial of exemestane for breast cancer prevention offers a potential new standard for pharmaceutical risk reduction in high-risk postmenopausal women. In addition to describing key findings from the publication of MAP.3 and related trials, our review undertakes a detailed analysis of the strengths and weaknesses of MAP.3 as well as the implications for future prevention research.
Xue et al demonstrate response and increased survival but development of acquired resistance to proteasome and Inhibitor-kappaB Kinase inhibitors targeting NF-kappa B activation in adenocarcinomas of Kras-activated, p53 deficient mice
Ubiquitin-specific protease 2a (USP2a) is overexpressed in almost half of human prostate cancers and c-Myc is amplified in one third of these tumor types. Transgenic MYC expression drives invasive adenocarcinomas in the murine prostate. We show that overexpression of USP2a downregulates a set of microRNAs that collectively increase MYC levels by MDM2 deubiquitination and subsequent p53 inactivation. By establishing MYC as a target of miR-34b/c, we demonstrate that this cluster functions as a tumor suppressor in prostate cancer cells. We identify a distinct mRNA signature that is enriched for MYC-regulated transcripts and transcription factor binding sites in USP2a overexpressing prostate cancer cells. We demonstrate that these genes are associated with an invasive phenotype in human prostate cancer and that the proliferative and invasive properties of USP2a overexpressing cells are MYC-dependent. These results highlight an unrecognized mechanism of MYC regulation in prostate cancer and suggest alternative therapeutic strategies in targeting MYC.
We explored diverse alterations contributing to liposarcomagenesis by sequencing the genome, exome, transcriptome, and cytosine methylome of a primary and recurrent dedifferentiated liposarcoma (DLPS) from distinct chemotherapy/radiotherapy-naïve patients. The liposarcoma genomes had complex structural rearrangements, but in different patterns, and with varied effects on the structure and expression of affected genes. While the point mutation rate was modest, integrative analyses and additional screening identified somatic mutations in HDAC1 in 8.3% of DLPS. Liposarcoma methylomes revealed alterations in differentiation pathway genes, including CEBPA methylation in 24% of DLPS. Treatment with demethylating agents, which restored CEBPA expression in DLPS cells, was anti-proliferative and pro-apoptotic in vitro and reduced tumor growth in vivo. Both genetic and epigenetic abnormalities established a role for small RNAs in liposarcomagenesis, typified by methylation-induced silencing of microRNA-193b in DLPS but not its well-differentiated counterpart. These findings reveal an unanticipated role for epigenetic abnormalities in DLPS tumors and suggest demethylating agents as potential therapeutics.
Dedifferentiated liposarcoma; DNA methylation; histone deacetylase; microRNA; adipocyte differentiation
A 48 year-old female with chemo-refractory metastatic gastric cancer to the liver was treated on a Phase I clinical trial with MetMAb, a monoclonal antibody targeting the Met tyrosine kinase receptor. The primary tumor had high MET gene polysomy and evidence for an autocrine production of HGF, the growth factor ligand of Met. A complete response was obtained lasting two years; the cancer recurred as a peritoneal deposit invading into the transverse colon and a gastrohepatic ligament node. Compassionate use of MetMAb therapy at recurrence achieved a mixed response - a partial response of the two initial lesions, but with development of multiple new foci of carcinomatosis. Tissue and serum studies evaluating the Met signaling pathway did correlate with MetMAb treatment response initially and at the time of recurrence.
Gastric adenocarcinoma; Met; HGF; MetMab
Epigenetic alterations are strongly associated with cancer development. We conducted a phase I/II trial of combined epigenetic therapy with azacitidine and entinostat, inhibitors of DNA methylation and histone deacetylation, respectively, in extensively pretreated patients with recurrent metastatic non-small cell lung cancer. This therapy is well tolerated, and objective responses were observed, including a complete response and a partial response in a patient who remains alive and without disease progression approximately 2 years after completing protocol therapy. Median survival in the entire cohort was 6.4 months (95% CI: 3.8–9.2), comparing favorably with existing therapeutic options. Demethylation of a set of four epigenetically silenced genes known to be associated with lung cancer was detectable in serial blood samples in these patients, and was associated with improved progression-free (p=0.034) and overall survival (p=0.035). Four of 19 patients had major objective responses to subsequent anti-cancer therapies given immediately following epigenetic therapy.
azacitidine; entinostat; demethylation; histone deacetylase inhibitor
Metastasis is a complex, multistep process that begins with the epithelial-mesenchymal transition (EMT). Circulating tumor cells (CTCs) are believed to have undergone EMT and thus lack or express low levels of epithelial markers commonly used for enrichment and/or detection of such cells. However, most current CTC detection methods only target EpCAM and/or cytokeratin to enrich epithelial CTCs, resulting in failure to recognize other, perhaps more important, CTC phenotypes that lack expression of these markers. Here, we describe a population of complex aneuploid CTCs that do not express cytokeratin or CD45 antigen in patients with breast, ovarian, or colorectal cancers. These cells were not observed in healthy subjects. We show that the primary epithelial tumors were characterized by similar complex aneuploidy, indicating conversion to an EMT phenotype in the captured cells. Collectively, our study provides a new method for highly efficient capture of previously unrecognized populations of CTCs.
Current assays for CTC capture likely miss populations of cells that have undergone EMT. Capture and study of CTCs that have undergone EMT would allow a better understanding of the mechanisms driving metastasis.
Cheung et al show that amplified CRKL can function as a driver oncogene in lung adenocarcinoma, activating both RAS and RAP1 to induce MAPK signaling. In addition, they show that CRKL amplification may be another mechanism for primary or acquired resistance to EGFR kinase inhibitors.
Although it is known that mTOR complex 2 (mTORC2) functions upstream of Akt, the role of this protein kinase complex in cancer is not well understood. Through an integrated analysis of cell lines, in vivo models and clinical samples, we demonstrate that mTORC2 is frequently activated in glioblastoma (GBM), the most common malignant primary brain tumor of adults. We show that the common activating epidermal growth factor receptor (EGFR) mutation (EGFRvIII) stimulates mTORC2 kinase activity, which is partially suppressed by PTEN. mTORC2 signaling promotes GBM growth and survival, and activates NF-κB. Importantly, this mTORC2-NF-κB pathway renders GBM cells and tumors resistant to chemotherapy in a manner independent of Akt. These results highlight the critical role of mTORC2 in GBM pathogenesis, including through activation of NF-κB downstream of mutant EGFR, leading to a previously unrecognized function in cancer chemotherapy resistance. These findings suggest that therapeutic strategies targeting mTORC2, alone or in combination with chemotherapy, will be effective in cancer.
EGFRvIII; mTORC2; Rictor; NF-κB; and chomotherapy resistance
The transcription factor NF-κB promotes survival of cancer cells exposed to doxorubicin and other chemotherapeutic agents. IκB kinase is essential for chemotherapy-induced NF-κB activation and considered a prime target for anticancer treatment. An IκB kinase inhibitor sensitized human melanoma xenografts in mice to killing by doxorubicin, yet also exacerbated treatment toxicity in the host animals. Using mouse models that simulate cell-selective targeting, we found that impaired NF-κB activation in melanoma and host myeloid cells accounts for the therapeutic and the adverse effects, respectively. Ablation of tumor-intrinsic NF-κB activity resulted in apoptosis-driven tumor regression following doxorubicin treatment. By contrast, chemotherapy in mice with myeloid-specific loss of NF-κB activation led to a massive intratumoral recruitment of interleukin-1β-producing neutrophils and necrotic tumor lesions, a condition associated with increased host mortality but not accompanied by tumor regression. Therefore, a molecular target-based therapy may be steered toward different clinical outcomes depending on the drug’s cell-specific effects.
NF-κB; melanoma; neutrophil; efficacy; toxicity
Activation of NF-κB has been linked to various cellular processes in cancer, including inflammation, transformation, proliferation, angiogenesis, invasion, metastasis, chemoresistance, and radioresistance. Although acute inflammation mediates innate and humoral immunity, chronic inflammation has been linked to tumorigenesis. Thus, inhibition of NF-κB has therapeutic potential in sensitization of tumors to chemotherapeutic agents; however, generalized suppression of NF-κB can result in serious host toxicity with minimum effect on the tumor.
Recent proteomic data have uncovered an interdependence of PI3K and STAT3. In PI3K-tranformed murine cells, STAT3 is phosphorylated on Y705 and activated in a PI3K-dependent manner. Dominant negative STAT3 interferes with PI3K-induced oncogenic transformation. Phosphorylation of STAT3 in PI3K-transformed murine cells is mediated by the TEC kinase BMX. Observations on glioblastoma stem cells reveal similar critical roles for STAT3 and BMX. The new data document an important role of STAT3 in PI3K-driven oncogenic transformation and mark BMX as a promising therapeutic target that could enhance the effectiveness of PI3K inhibitors.
SILAC; TEC kinase; TOR; PH domain; BMX
Neuroendocrine prostate cancer (NEPC) is an aggressive subtype of prostate cancer that most commonly evolves from preexisting prostate adenocarcinoma (PCA). Using Next Generation RNA-sequencing and oligonucleotide arrays, we profiled 7 NEPC, 30 PCA, and 5 benign prostate tissue (BEN), and validated findings on tumors from a large cohort of patients (37 NEPC, 169 PCA, 22 BEN) using IHC and FISH. We discovered significant overexpression and gene amplification of AURKA and MYCN in 40% of NEPC and 5% of PCA, respectively, and evidence that that they cooperate to induce a neuroendocrine phenotype in prostate cells. There was dramatic and enhanced sensitivity of NEPC (and MYCN overexpressing PCA) to Aurora kinase inhibitor therapy both in vitro and in vivo, with complete suppression of neuroendocrine marker expression following treatment. We propose that alterations in Aurora kinase A and N-myc are involved in the development of NEPC, and future clinical trials will help determine from the efficacy of Aurora kinase inhibitor therapy.
neuroendocrine prostate cancer; aurora kinase A; n-myc; drug targets
We report that IL-17 significantly increases the secretion of CXCL1 and CXCL5 from mammary carcinoma cells, which is downregulated by TGF-β through the type II TGF-β receptor (TβRII). Carcinoma cells with conditional knockout of TβRII (Tgfbr2KO) have enhanced sensitivity to IL-17a in the stimulation of chemokine secretion. During polyoma middle T (PyMT) induced tumor progression, levels of Th17 inducing cytokines TGF-β, IL-6, IL-23 were increased in PyMT/Tgfbr2KO tumors, which was associated with an increased number of Th17 cells. IL-17 increased the suppressive function of MDSCs on T cells through the upregulation of Arg, IDO, and COX2. Treatment of PyMT/Tgfbr2KO mice with anti-IL-17 Ab decreased carcinoma growth and metastatic burden. Analysis of human breast cancer transcriptome databases showed a strong association between IL-17 gene expression and poor outcome in lymph node positive, estrogen receptor negative or luminal B subtypes suggesting potential therapeutic approaches.
Target groups for human papillomavirus (HPV) vaccination are controversial. We evaluated vaccine efficacy (VE) against 1-year persistent infection, stratified by age and sexual behavior, among young women in Costa Rica. We randomized 7,466 healthy women 18 to 25 years of age to HPV16/18 or hepatitis A vaccine (follow-up, 50.4 months). According-to-protocol (ATP) cohorts included compliant HPV-negative women; intention-to-treat (ITT) included all randomized women. ATP VE was 90.9% (95% CI, 82.0–95.9) against HPV16/18 infections, 44.5% against HPV31/33/45 (95% CI, 17.5–63.1), and 12.4% (95% CI, −3.2 to 25.6) against any oncogenic infection. Overall ITT VE against HPV16/18 infections was 49.0%, but ATP and ITT VE almost reached 100% in year 4 of follow-up. ATP efficacy against HPV16/18 was similar by age, but ITT VE was greatest among youngest women (68.9% among those 18–19 years of age; 21.8% among those 24–25 years of age) and 79.8% among virgins. Among previously unexposed women, vaccination is highly efficacious against HPV16/18 and partially against HPV31/33/45. Vaccination is most effective in women and girls before they initiate sexual activity, with programmatic and individual decision implications.
The anti-diabetic drug metformin has anti-tumor activity in a variety of cancers because it blocks cell growth by inhibiting TORC1. Here we show that melanoma cells that are driven by oncogenic BRAF are resistant to the growth-inhibitory effects of metformin because RSK sustains TORC1 activity even when AMPK is activated. We further show that AMPK targets the dual-specificity protein phosphatase DUSP6 for degradation and this increases ERK activity, which then upregulates the VEGF-A protein. Critically, this drives angiogenesis and accelerates the growth of BRAF-driven tumors in mice. Unexpectedly however, when VEGF signaling is inhibited, instead of accelerating tumor growth, metformin inhibits tumor growth. Thus, we show that BRAF-driven melanoma cells are resistant to the anti-growth effects of AMPK and that AMPK mediates cell autonomous and cell non-autonomous effects that accelerate the growth of these cells in vivo.
BRAFV600E; melanoma; metformin; AMPK; VEGF
Cancers with specific genetic mutations are susceptible to selective kinase inhibitors. However, there is wide spectrum of benefit among cancers harboring the same sensitizing genetic mutations. Herein, we measured apoptotic rates among cell lines sharing the same driver oncogene following treatment with the corresponding kinase inhibitor. There was a wide range of kinase inhibitor-induced apoptosis despite comparable inhibition of the target and associated downstream signaling pathways. Surprisingly, pre-treatment RNA levels of the BH3-only pro-apoptotic BIM strongly predicted the capacity of EGFR, HER2, and PI3K inhibitors to induce apoptosis in EGFR mutant, HER2 amplified, and PIK3CA mutant cancers, respectively, but BIM levels did not predict responsiveness to standard chemotherapies. Furthermore, BIM RNA levels in EGFR mutant lung cancer specimens predicted response and duration of clinical benefit from EGFR inhibitors. These findings suggest assessment of BIM levels in treatment naïve tumor biopsies may indicate the degree of benefit from single-agent kinase inhibitors in multiple oncogene-addiction paradigms.
BIM; oncogene addiction; apoptosis; EGFR; HER2
An increasing number of anti-cancer therapeutic agents target specific mutant proteins that are expressed by many different tumor types. Recent evidence suggests that the selection of patients whose tumors harbor specific genetic alterations identifies the subset of patients that are most likely to benefit from the use of such agents. As the number of genetic alterations that provide diagnostic and/or therapeutic information increases, the comprehensive characterization of cancer genomes will be necessary to understand the spectrum of distinct genomic alterations in cancer, to identify patients who are likely to respond to particular therapies and to facilitate the selection of treatment modalities. Rapid developments in new technologies for genomic analysis now provide the means to perform comprehensive analyses of cancer genomes. Here we review the current state of cancer genome analysis and discuss the challenges and opportunities necessary to implement these technologies in a clinical setting.