Ewing sarcoma (ES) is the second most common bone tumor in children and young adults, with dismal outcomes for metastatic and relapsed disease. To better understand the molecular pathogenesis of ES and to identify new prognostic markers, we used molecular inversion probes (MIPs) to evaluate copy number alterations (CNAs) and loss of heterozygosity (LOH) in formalin-fixed paraffin-embedded (FFPE) samples which included 40 ES primary tumors and 12 ES metastatic lesions. CNAs were correlated with clinical features and outcome, and validated by immunohistochemistry (IHC). We identified previously reported CNAs, in addition to SMARCB1 (INI1/SNF5) homozygous loss and copy neutral LOH. IHC confirmed SMARCB1 protein loss in 7–10% of clinically-diagnosed ES tumors in three separate cohorts (University of Utah [N=40], Children’s Oncology Group [N=31], and University of Michigan [N=55]). A multifactor copy number (MCN)-index was highly predictive of overall survival (39% vs. 100%, P<0.001). We also identified RELN gene deletions unique to 25% of ES metastatic samples. In summary, we identified both known and novel CNAs using MIP technology for the first time in FFPE samples from patients with ES. CNAs detected by microarray correlate with outcome and may be useful for risk-stratification in future clinical trials.
Ewing sarcoma; copy number; outcome; SMARCB1/INI1/SNF5; CEBPB
Background & Aims
Although hepatocellular cancers (HCC) frequently arise in the setting of fibrosis and a hepatic regenerative response requiring new cell growth, therapeutic strategies for these cancers have not targeted protein synthesis. Silvestrol, a rocaglate isolated from Aglaiafoveolata, can inhibit protein synthesis by modulating the initiation of translation through the eukaryotic initiation factor 4A. In this study, we evaluated the therapeutic efficacy of silvestrol for HCC.
The efficacy of silvestrol was examined using human HCC cells in
vitro using an orthotopic tumor cell xenograft model in a fibrotic liver. The impact of silvestrol on the liver was assessed in
vivo in wild-type mice.
Silvestrol inhibited cell growth with an IC50 of 12.5-86 nM in four different HCC cell lines. In
vitro, silvestrol increased apoptosis and caspase 3/7 activity accompanied by loss of mitochondrial membrane potential and decreased expression of Mcl-1 and Bcl-xL. A synergistic effect was observed when silvestrol was combined with other therapeutic agents, with a dose-reduction index of 3.42-fold with sorafenib and 1.75-fold with rapamycin at a fractional effect of 0.5. In
vivo, an antitumor effect was observed with 0.4 mg/kg silvestrol compared to controls after one week, and survival of tumor-bearing mice was improved with a median survival time of 42 and 28 days in the silvestrol and control groups, respectively. The effect on survival was not observed in orthotopic xenografts in non-fibrotic livers. Silvestrol treatment in
vivo did not alter liver structure.
These data identify silvestrol as a novel, structurally unique drug with potent anticancer activity for HCC and support the potential value of targeting initiation of translation in the treatment of HCC.
The use of neoadjuvant and adjuvant chemotherapy in soft tissue sarcomas is controversial. This is a report of long-term (≥5 years) follow-up in patients with high-grade, high-risk soft tissue sarcomas treated with neoadjuvant chemotherapy, preoperative radiotherapy (RT), and adjuvant chemotherapy.
Patients with high-grade soft tissue sarcoma ≥8 cm in diameter of the extremities and body wall received 3 cycles of neoadjuvant chemotherapy (mesna, doxorubicin, ifosfamide, and dacarbazine) and preoperative RT (44 grays administered in split courses), and 3 cycles of postoperative chemotherapy (mesna, doxorubicin, ifosfamide, and dacarbazine).
Sixty-four of 66 patients were analyzed. After chemotherapy and RT, 61 patients had surgery; 58 had R0 resections (5 amputations), and 3 had R1 resections. Ninety-seven percent experienced grade 3 or higher toxicity, including 3 deaths. These toxicities were short term. With a median follow-up of 7.7 years in surviving patients, the 5-year rates of locoregional failure (including amputation), and distant metastasis were 22.2% (95% confidence interval [CI], 11.8–32.6) and 28.1% (95% CI, 17.0–39.2). The most common site of metastasis was lung. Estimated 5-year rates of disease-free survival, distant disease-free survival, and overall survival were 56.1% (95% CI, 43.9–68.3), 64.1% (95% CI, 52.3–75.8), and 71.2% (95% CI, 60.0–82.5), respectively.
Although the toxicity was significant, it was limited in its course and for the most part resolved by 1 year. The long-term outcome was better than might be expected in such high-risk tumors.
sarcoma; neoadjuvant chemotherapy; radiation
Angiosarcomas are aggressive tumors of vascular endothelial origin, occurring sporadically or in association with prior radiotherapy. We compared clinicopathologic and biologic features of sporadic angiosarcomas (SA) and radiation-associated angiosarcomas (RAA). Methods. From a University of Michigan institutional database, 37 SA and 11 RAA were identified. Tissue microarrays were stained for p53, Ki-67, and hTERT. DNA was evaluated for TP53 and ATM mutations. Results. Mean latency between radiotherapy and diagnosis of RAA was 11.9 years: 6.7 years for breast RAA versus 20.9 years for nonbreast RAA (P = 0.148). Survival after diagnosis did not significantly differ between SA and RAA (P = 0.590). Patients with nonbreast RAA had shorter overall survival than patients with breast RAA (P = 0.03). The majority of SA (86.5%) and RAA (77.8%) were classified as high-grade sarcomas (P = 0.609). RAA were more likely to have well-defined vasoformative areas (55.6% versus 27%, P = 0.127). Most breast SA were parenchymal in origin (80%), while most breast RAA were cutaneous in origin (80%). TMA analysis showed p53 overexpression in 25.7% of SA and 0% RAA, high Ki-67 in 35.3% of SA and 44.4% RAA, and hTERT expression in 100% of SA and RAA. TP53 mutations were detected in 13.5% of SA and 11.1% RAA. ATM mutations were not detected in either SA or RAA. Conclusions. SA and RAA are similar in histology, immunohistochemical markers, and DNA mutation profiles and share similar prognosis. Breast RAA have a shorter latency period compared to nonbreast RAA and a significantly longer survival.
During cell cycle progression, D-cyclins activate cyclin-dependent kinases (CDKs) 4/6 to inactivate Rb, permitting E2F1-mediated S-phase gene transcription. This critical pathway is typically deregulated in cancer, and novel inhibitory strategies would be effective in a variety of tumors. The protein synthesis inhibitor silvestrol has potent activity in B-cell leukemias via the mitochondrial pathway of apoptosis, and also reduces cyclin D1 expression in breast cancer and lymphoma cell lines. We hypothesized that this dual activity of silvestrol would make it especially effective in malignancies driven by aberrant cyclin D1 expression.
Mantle Cell Lymphoma (MCL), characterized by elevated cyclin D1, was used as a model to test this approach. The cyclin D/Rb/E2F1 pathway was investigated in vitro using MCL cell lines and primary tumor cells. Silvestrol was also evaluated in vivo using an aggressive model of MCL.
Silvestrol showed low nanomolar potency both in MCL cell lines and primary MCL tumor cells. D-cyclins were depleted with just 10 nM silvestrol at 16 hr, with subsequent reductions of phosphorylated Rb, E2F1 protein, and E2F1 target transcription. As demonstrated in other leukemias, silvestrol caused Mcl-1 depletion followed by mitochondrial depolarization and caspase-dependent apoptosis, effects not related to inhibition of CDK4/6. Silvestrol significantly (P<0.0001) prolonged survival in a MCL xenograft model without detectable toxicity.
These data indicate that silvestrol effectively targets the cyclin/CDK/Rb pathway, and additionally induces cytotoxicity via intrinsic apoptosis. This dual activity may be an effective therapeutic strategy in MCL and other malignancies.
translation; cyclin; Rb; lymphoma; cell cycle
The impact of mutation of the ATM (ataxia telangiectasia mutated) gene in chronic lymphocytic leukemia (CLL) treatment outcome has not been examined. We studied ATM mutations in 73 patients treated with fludarabine and rituximab. ATM gene mutation analysis was performed using temperature gradient capillary electrophoresis. The impact of detected variants on overall survival (OS) and progression-free survival (PFS) was tested with proportional hazards models. None of the 73 patients demonstrated truncating ATM mutations; 17 (23%, 95% confidence interval 14 – 35%) had non-silent variants (ATM-NSVs), including 13 known ATM polymorphisms and four missense variants. ATM-NSVs were not significantly associated with any baseline characteristics including immunoglobulin heavy chain variable gene (IGVH) status. In multivariable models, no significant differences in complete response (p = 0.70), PFS (p = 0.59) or OS (p = 0.13) were observed. Our data indicate that truncating ATM mutations are rare in patients with CLL. Furthermore, in this dataset, these non-silent variants had limited impact on PFS and OS.
Chronic lymphocytic leukemia; ATM mutation; prognosis; chemoimmunotherapy
Increased ZAP-70 expression predicts poor prognosis in chronic lymphocytic leukemia (CLL). Current methods for accurately measuring ZAP-70 expression are problematic, preventing widespread application of these tests in clinical decision making. We therefore used comprehensive DNA methylation profiling of the ZAP-70 regulatory region to identify sites important for transcriptional control.
Patients and Methods
High-resolution quantitative DNA methylation analysis of the entire ZAP-70 gene regulatory regions was conducted on 247 samples from patients with CLL from four independent clinical studies.
Through this comprehensive analysis, we identified a small area in the 5′ regulatory region of ZAP-70 that showed large variability in methylation in CLL samples but was universally methylated in normal B cells. High correlation with mRNA and protein expression, as well as activity in promoter reporter assays, revealed that within this differentially methylated region, a single CpG dinucleotide and neighboring nucleotides are particularly important in ZAP-70 transcriptional regulation. Furthermore, by using clustering approaches, we identified a prognostic role for this site in four independent data sets of patients with CLL using time to treatment, progression-free survival, and overall survival as clinical end points.
Comprehensive quantitative DNA methylation analysis of the ZAP-70 gene in CLL identified important regions responsible for transcriptional regulation. In addition, loss of methylation at a specific single CpG dinucleotide in the ZAP-70 5′ regulatory sequence is a highly predictive and reproducible biomarker of poor prognosis in this disease. This work demonstrates the feasibility of using quantitative specific ZAP-70 methylation analysis as a relevant clinically applicable prognostic test in CLL.
We evaluated the safety and efficacy of the purine nucleoside analogue, clofarabine, in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL). Six patients with DLBCL (n = 5) or MCL (n = 1) and a median age of 68 years were treated with 40 mg/m2 clofarabine IV over 2 h for 5 days, repeated every 28 days, for 1–2 cycles. The overall response rate was 50% (complete response = 1, complete response unconfirmed = 1, partial response = 1). Median progression-free survival was 3.5 months (range 1.5–10 months) and the median overall survival was 7.8 months (range 3–31 months). Grade 3–4 neutropenia and thrombocytopenia was universal, with a median of 34 (range 19–55) and 77 (range 0–275) days required for neutrophil and platelet recovery. Grade 3 non-hematologic toxicities included transaminitis, febrile neutropenia, non-neutropenic infections and orthostatic hypotension. Further accrual to the study was terminated due to prolonged Grade 3–4 myelosuppression and orthostatic hypotension in five of six patients. Clofarabine exhibits evidence of single agent activity in relapsed or refractory DLBCL. However, further study with novel administration schedules that maintain this efficacy and limit toxicity is warranted.
Clofarabine; diffuse large B cell lymphoma; mantle cell lymphoma; nucleoside analogues; myelosuppression
Tetraspanins are commonly believed to act only as “molecular facilitators”, with no direct role in signal transduction. We herein demonstrate that upon ligation, CD37, a tetraspanin molecule expressed on mature normal and transformed B-cells, becomes tyrosine phosphorylated, associates with proximal signaling molecules, and initiates a cascade of events leading to apoptosis. Moreover, we have identified two tyrosine residues with opposing regulatory functions, one lies in the N-terminal domain of CD37 in a predicted “ITIM-like” motif and mediates SHP1-dependent death whereas the second lies in a predicted “ITAM motif” in the C-terminal domain of CD37 and counteracts death signals by mediating phosphatidylinositol 3-kinase-dependent survival.
Activating mutations [internal tandem duplication (ITD)] or overexpression of the FMS-like tyrosine kinase receptor-3 (FLT3) gene are associated with poor outcome in acute myeloid leukemia (AML) patients, underscoring the need for novel therapeutic approaches. The natural product silvestrol has potent antitumor activity in several malignancies, but its therapeutic impact on distinct molecular high-risk AML subsets remains to be fully investigated. We examined here the preclinical activity of silvestrol in FLT3-ITD and FLT3 wild-type (wt) AML.
Silvestrol in vitro anti-leukemic activity was examined by colorimetric cell viability assay, colony-forming and flow cytometry assays assessing growth inhibition and apoptosis, respectively. Pharmacological activity of silvestrol on FLT3 mRNA translation, mRNA and protein expression was determined by RNA-immunoprecipitation, qRT-PCR and immunoblot analyses, respectively. Silvestrol in vivo efficacy was investigated using MV4-11 leukemia-engrafted mice.
Silvestrol shows antileukemia activity at nanomolar concentrations both in FLT3-wt overexpressing (THP-1) and FLT3-ITD (MV4-11) expressing AML cell lines (IC50 = 3.8 and 2.7 nM, respectively) and patients’ primary blasts [IC50 = ~12 nM (FLT3-wt) and ~5 nM (FLT3-ITD)]. Silvestrol increased apoptosis (~4fold, P = 0.0001), and inhibited colony-formation (100%, P < 0.0001) in primary blasts. Silvestrol efficiently inhibited FLT3 translation reducing FLT3 protein expression by 80–90% and decreased miR-155 levels (~60%), a frequently co-regulated onco-miR in FLT3-ITD-positive AML. The median survival of silvestrol-treated vs vehicle-treated mice was 63 vs 29 days post-engraftment, respectively (P < 0.0001).
Silvestrol exhibits significant in vivo and in vitro antileukemic activities in AML through a novel mechanism resulting in inhibition of FLT3 and miR-155 expression. These encouraging results warrant a rapid translation of silvestrol for clinical testing in AML.
A phase I study to determine the maximum tolerated dose (MTD) of bortezomib (B) when combined with weekly paclitaxel in patients with advanced solid tumors.
Patients and methods
Eligible patients received escalating doses of intravenous (IV) bortezomib (0.6–2 mg/m2) on days 2 and 9 and IV paclitaxel at 100 mg/m2 on days 1 and 8 of a 21-day cycle. Dose escalation was based on two end-points: not exceeding 80% 20S-proteasome inhibition (20-S PI) and the development of dose-limiting toxicity defined as grade 3 or greater non-hematologic or grade 4 hematologic toxicities.
Forty-five patients with advanced solid tumors and a median of 3 prior chemotherapy regimens (range 0– 9), received 318 doses (median 5, range 1–34) of bortezomib and paclitaxel. Dose-related inhibition of 20-S PI was observed with a maximum inhibition of 70–80% at the MTD of 1.8 mg/m2 of bortezomib. At the MTD (N = 9) the following toxicities were observed: grade 4 neutropenia without fever (n = 2) and cerebrovascular ischemia (n = 1); grade 3 neutropenia (n = 3), diarrhea (n = 2), nausea (n = 1), and fatigue (n = 1); grade 2 fatigue (n = 5), diarrhea (n = 4), and dyspnea (n = 2). There was one partial response in a patient with an eccrine porocarcinoma. Stabilization of disease was observed in 7 (16%) patients, 3 of whom had advanced pancreatic cancer.
Sequential paclitaxel and bortezomib in previously treated patients with advanced solid tumors resulted in acceptable toxicity and no evidence of interaction. The recommended phase II dose of bortezomib in combination with weekly paclitaxel was 1.8 mg/m2.
Bortezomib; Phase I; Solid tumors; Paclitaxel
The analysis of proteins by reversed-phase liquid chromatography (RPLC) commonly involves the use of TFA as an ion-pairing agent, even though it forms adducts and suppresses sensitivity. The presence of adducts can complicate protein molecular weight assignment especially when protein isoforms coelute as in the case of histones. To mitigate the complicating effects of TFA adducts in protein LC-MS, we have optimized TFA-free methods for protein separation. Protein standards and histones were used to evaluate TFA-free separations using capillary (0.3 mm id) and nanoscale (0.1 mm id) C8 columns with the ion-pairing agents, formic acid or acetic acid. The optimized method was then used to examine the applicability of the approach for histone characterization in human cancer cell lines and primary tumor cells from chronic lymphocytic leukemia patients.
Histone; RPLC-MS; TFA-free; capillary/nanoscale separation
Protein synthesis is a powerful therapeutic target in leukemias and other cancers, but few pharmacologically viable agents are available that affect this process directly. The plant-derived agent silvestrol specifically inhibits translation initiation by interfering with eIF4A/mRNA assembly with eIF4F. Silvestrol has potent in vitro and in vivo activity in multiple cancer models including acute lymphoblastic leukemia (ALL) and is under pre-clinical development by the US National Cancer Institute, but no information is available about potential mechanisms of resistance. In a separate report, we showed that intraperitoneal silvestrol is approximately 100% bioavailable systemically, although oral doses were only 1% bioavailable despite an apparent lack of metabolism. To explore mechanisms of silvestrol resistance and the possible role of efflux transporters in silvestrol disposition, we characterized multi-drug resistance transporter expression and function in a silvestrol-resistant ALL cell line generated via culture of the 697 ALL cell line in gradually increasing silvestrol concentrations. This resistant cell line, 697-R, shows significant upregulation of ABCB1 mRNA and P-glycoprotein (Pgp) as well as cross-resistance to known Pgp substrates vincristine and romidepsin. Furthermore, 697-R cells readily efflux the fluorescent Pgp substrate rhodamine 123. This effect is prevented by Pgp inhibitors verapamil and cyclosporin A, as well as siRNA to ABCB1, with concomitant re-sensitization to silvestrol. Together, these data indicate that silvestrol is a substrate of Pgp, a potential obstacle that must be considered in the development of silvestrol for oral delivery or targeting to tumors protected by Pgp overexpression.
ABCB1; leukemia; multi-drug resistance; P-glycoprotein; silvestrol
A sensitive and specific liquid chromatography–tandem mass spectrometry method was developed and validated for the quantification of the plant natural product silvestrol in mice, using ansamitocin P-3 as the internal standard. The method was validated in plasma with a lower limit of quantification of 1 ng/mL, accuracy ranging from 87 to 114%, and precision (coefficient of variation) below 15%. The validated method was used to characterize pharmacokinetics in C57BL/6 mice and metabolism in mouse, human and rat plasma, and liver microsomes. Mice were dosed with silvestrol formulated in hydroxypropyl-β-cyclodextrin via intravenous, intraperitoneal, and oral routes followed by blood sampling up to 24 h. Intraperitoneal systemic availability was 100%, but oral administration resulted in only 1.7% bioavailability. Gradual degradation of silvestrol was observed in mouse and human plasma, with approximately 60% of the parent drug remaining after 6 h. In rat plasma, however, silvestrol was completely converted to silvestric acid (SA) within 10 min. Evaluation in microsomes provided further evidence that the main metabolite formed was SA, which subsequently showed no cytotoxic or cytostatic activity in a silvestrol-sensitive lymphoblastic cell line. The ability of the analytical assay to measure tissue levels of silvestrol was evaluated in liver, brain, kidney, and spleen. Results indicated the method was capable of accurately measuring tissue levels of silvestrol and suggested it has a relatively low distribution to brain. Together, these data suggest an overall favorable pharmacokinetic profile of silvestrol in mice and provide crucial information for its continued development toward potential clinical testing.
liquid chromatography–tandem mass spectrometry; mouse plasma; pharmacokinetics; silvestrol
Effective quantitative profiling of detergent-insoluble membrane proteins using high-throughput mass spectrometry (MS)-based proteomics would allow a better understanding of physiological and pathological processes that take place at the cell surface. To increase the coverage of proteins present in detergent-resistant membrane microdomains (DRMMs), a combination of 16O/18O and isotope coded affinity tags (ICAT) labeling was used in a comparative analysis of detergent-insoluble membrane proteins isolated from rat basophilic leukemia cells (RBL-2H3), with either Triton X-100 or Brij-96. The analysis resulted in the quantification of 738 unique proteins from Triton X-100 and Brij-96 isolated DRMMs, significantly exceeding the number of proteins quantified from either single labeling technique. Twenty-five non-cysteine-containing proteins were quantified, as well as 32 cysteine-containing proteins that would have been missed if either 16O/18O or ICAT labeling had been used exclusively, which illustrate better proteome coverage and enhanced ability to quantitate. The comparative analysis revealed that proteins were more readily extracted using Triton X-100 than Brij-96; however, Triton X-100 also extracted larger quantities of non-DRMMs-associated proteins. This result confirms previous, targeted studies suggesting that DRMMs isolated using Triton X-100 and Brij-96 differ in their protein content.
Quantitative proteomics; combined 16O/18O and ICAT stable isotopic labeling; Triton X-100 and Brij-96 detergent-insoluble membrane proteins
Hematologic malignancies account for a substantial percentage of cancers worldwide, and the heterogeneity and biological characteristics of leukemias and lymphomas present unique therapeutic challenges. Although treatment options exist for most of these diseases, many types remain incurable and the emergence of drug resistance is pervasive. Thus, novel treatment approaches are essential to improve outcome. Nearly half of the agents used in cancer therapy today are either natural products or derivatives of natural products. The enormous chemical diversity in nature, coupled with millennia of biological selection, has generated a vast and underexplored reservoir of unique chemical structures with biologic activity. This review will describe the investigation and application of natural products derived from higher plants in the treatment of leukemia and lymphoma and the rationale behind these efforts. In addition to the approved vinca alkaloids and the epipodophyllotoxin derivatives, a number of other plant compounds have shown promise in clinical trials and in preclinical investigations. In particular, we will focus on the discovery and biological evaluation of the plant-derived agent silvestrol, which shows potential for additional development as a new therapeutic agent for B-cell malignancies including chronic lymphocytic leukemia.
Epipodophylloxin derivatives; flavopiridol; hematological malignancies; leukemia; lymphoma; natural products; silvestrol; vinca alkaloids
Targeting aberrant DNA hypermethylation in chronic lymphocytic leukemia (CLL) and non-Hodgkin’s lymphoma (NHL) with decitabine may reverse epigenetic silencing in B-cell malignancies.
Twenty patients were enrolled in two phase I trials to determine the minimum effective pharmacologic dose (MEPD) of decitabine in patients with relapsed/refractory CLL (n=16) and NHL (n=4).
Patients received 1–3 cycles of decitabine. Dose limiting toxicity (DLT) was observed in 2 of 4 CLL and 2 of 2 NHL patients receiving decitabine at 15 mg/m2/d days 1–10, consisting of grade 3–4 thrombocytopenia and hyperbilirubinemia. Six patients with CLL received decitabine at 10 mg/m2/d days 1–10 without DLT; however, re-expression of methylated genes or changes in global DNA methylation were not observed. Therefore, a 5-day decitabine schedule was examined. With 15 mg/m2/d decitabine days 1–5, DLT occurred in 2 of 6 CLL and 2 of 2 NHL patients, consisting of grade 3–4 neutropenia, thrombocytopenia, and febrile neutropenia. Eight patients had stable disease. In 17 patients, there were no significant changes in genome-wide methylation or in target gene re-expression.
Dose-limiting myelosuppression and infectious complications prevents dose escalation of decitabine to levels associated with changes in global methylation or gene re-expression in CLL and NHL.
decitabine; methylation; chronic lymphocytic leukemia; non-Hodgkin’s lymphoma
The in vitro evaluation of histones and their post-translational modifications has drawn substantial interest in the development of epigenetic therapies. The differential expression of histone isoforms may serve as a potential marker in the classification of diseases affected by chromatin abnormalities. In this study, protein profiling by liquid chromatography and mass spectrometry was used to explore differences in histone composition in primary CLL cells. Extensive method validations were performed to determine the experimental variances that would impact histone relative abundance. The resulting data demonstrated that the proposed methodology was suitable for the analysis of histone profiles. In 4 normal individuals and 40 CLL patients, a significant decrease in the relative abundance of histone H2A variants (H2AFL and H2AFA/M*) was observed in primary CLL cells as compared to normal B cells. Protein identities were determined using high mass accuracy mass spectrometry and shotgun proteomics.
Chronic lymphocytic leukemia; histone; variant; RPLC-MS
Previous studies in our laboratory have shown the progressive methylation and suppression of the gene encoding protein tyrosine phosphatase, PTPRO, in the livers of rats fed a methyl-deficient diet that induces hepatocarcinogenesis. Subsequently, we observed the methylation of PTPRO in primary human lung tumors and also showed its potential tumor suppressor characteristics. The present study was undertaken to investigate whether the truncated form of PTPRO (PTPROt), specifically expressed in naïve B lymphocytes, was also methylated and suppressed in chronic lymphocytic leukemia (CLL), a disease generally affecting B lymphocytes.
Experimental Design and Results
Initial screening showed that 60% of the 52 CLL samples analyzed using methylation-specific PCR assay were methylated compared with B lymphocytes from normal individuals, which were not methylated. The expression of PTPROt, as measured by semiquantitative reverse transcription-PCR, inversely correlated with methylation in the few samples tested. Analysis of additional samples (n = 50) by combined bisulfite restriction analysis showed that the PTPRO CpG island was methylated in 82% of patients with CLL compared with B lymphocytes from normal individuals. Furthermore, overall expression of PTPRO was reduced in CLL relative to normal lymphocytes. The PTPRO gene was also suppressed by methylation in the CLL cell lineWaC3CD5, where it could be reactivated upon treatment with the DNA hypome-thylating agent 5-AzaC. Ectopic expression of PTPROt in a nonexpressing cell line increased growth inhibition with fludarabine treatment, a therapy commonly used for CLL.
This study reveals the potential role of PTPRO methylation and silencing in CLL tumorigenesis and also provides a novel molecular target in the epigenetic therapy.
Spatially invariant vector quantization (SIVQ) is a texture and color-based image matching algorithm that queries the image space through the use of ring vectors. In prior studies, the selection of one or more optimal vectors for a particular feature of interest required a manual process, with the user initially stochastically selecting candidate vectors and subsequently testing them upon other regions of the image to verify the vector's sensitivity and specificity properties (typically by reviewing a resultant heat map). In carrying out the prior efforts, the SIVQ algorithm was noted to exhibit highly scalable computational properties, where each region of analysis can take place independently of others, making a compelling case for the exploration of its deployment on high-throughput computing platforms, with the hypothesis that such an exercise will result in performance gains that scale linearly with increasing processor count.
An automated process was developed for the selection of optimal ring vectors to serve as the predicate matching operator in defining histopathological features of interest. Briefly, candidate vectors were generated from every possible coordinate origin within a user-defined vector selection area (VSA) and subsequently compared against user-identified positive and negative “ground truth” regions on the same image. Each vector from the VSA was assessed for its goodness-of-fit to both the positive and negative areas via the use of the receiver operating characteristic (ROC) transfer function, with each assessment resulting in an associated area-under-the-curve (AUC) figure of merit.
Use of the above-mentioned automated vector selection process was demonstrated in two cases of use: First, to identify malignant colonic epithelium, and second, to identify soft tissue sarcoma. For both examples, a very satisfactory optimized vector was identified, as defined by the AUC metric. Finally, as an additional effort directed towards attaining high-throughput capability for the SIVQ algorithm, we demonstrated the successful incorporation of it with the MATrix LABoratory (MATLAB™) application interface.
The SIVQ algorithm is suitable for automated vector selection settings and high throughput computation.
Automatic vector selection; MATLAB; parallel computing; SIVQ; histology; image analysis; pattern recognition
MGCD0103, an orally available class I histone deacetylase (HDAC) inhibitor, was examined for pre-clinical activity in chronic lymphocytic leukaemia (CLL). A phase II clinical trial was performed, starting at a dose of 85 mg/day, three times per week. Dose escalation to 110 mg or the addition of rituximab was permitted in patients without a response after 2 or more cycles. MGCD0103 demonstrated pre-clinical activity against CLL cells with a LC50 (concentration lethal to 50%) of 0.23 μM and increased acetylation of the HDAC class I specific target histone H3. Twenty-one patients received a median of 2 cycles of MGCD0103 (range, 0–12). All patients had previously received fludarabine, 33% were fludarabine refractory, and 71% had del(11q22.3) or del(17p13.1). No responses according to the National Cancer Institutes 1996 criteria were observed. Three patients received 110 mg and 4 patients received concomitant rituximab, with no improvement in response. Grade 3–4 toxicity consisted of infections, thrombocytopenia, anemia, diarrhea, and fatigue. HDAC inhibition was observed in 6 out of 9 patients on day 8. Limited activity was observed with single agent MGCD0103 in high risk patients with CLL. Future investigations in CLL should focus on broad HDAC inhibition, combination strategies, and approaches to diminish constitutional symptoms associated with this class of drugs.
Chronic lymphocytic leukemia; MGCD0103; histone deacetylase inhibitors; epigenetics
While deacetylase (DAC) inhibitors show promise for the treatment of B-cell malignancies, those introduced to date are weak inhibitors of class I and II DACs or potent inhibitors of class I DAC only, and have shown suboptimal activity or unacceptable toxicities. We therefore investigated the novel DAC inhibitor AR-42 to determine its efficacy in B-cell malignancies.
In mantle cell lymphoma (JeKo-1), Burkitt's lymphoma (Raji), and acute lymphoblastic leukemia (697) cell lines, the 48-hr IC50 (50% growth inhibitory concentration) of AR-42 is 0.61 µM or less. In chronic lymphocytic leukemia (CLL) patient cells, the 48-hr LC50 (concentration lethal to 50%) of AR-42 is 0.76 µM. AR-42 produces dose- and time-dependent acetylation both of histones and tubulin, and induces caspase-dependent apoptosis that is not reduced in the presence of stromal cells. AR-42 also sensitizes CLL cells to TNF-Related Apoptosis Inducing Ligand (TRAIL), potentially through reduction of c-FLIP. AR-42 significantly reduced leukocyte counts and/or prolonged survival in three separate mouse models of B-cell malignancy without evidence of toxicity.
Together, these data demonstrate that AR-42 has in vitro and in vivo efficacy at tolerable doses. These results strongly support upcoming phase I testing of AR-42 in B-cell malignancies.
Mantle cell lymphoma (MCL) is a distinct histologic subtype of B cell non-Hodgkins lymphoma (NHL) associated with an aggressive clinical course. Inhibition of the ubiquitin-proteasome pathway modulates survival and proliferation signals in MCL and has shown clinical benefit in this disease. This has provided rationale for exploring combination regimens with B-cell selective immunotherapies such as rituximab. In this study, we examined the effects of combined treatment with bortezomib and rituximab on patient-derived MCL cell lines (Jeko, Mino, SP53) and tumor samples from patients with MCL where we validate reversible proteasome inhibition concurrent with cell cycle arrest and additive induction of apoptosis. When MCL cells were exposed to single agent bortezomib or combination bortezomib/rituximab, caspase dependent and independent apoptosis was observed. Single agent bortezomib or rituximab treatment of Mino and Jeko cell lines and patient samples resulted in decreased levels of nuclear NFκB complex(es) capable of binding p65 consensus oligonucleotides, and this decrease was enhanced by the combination. Constitutive activation of the Akt pathway was also diminished with bortezomib alone or in combination with rituximab. On the basis of in vitro data demonstrating additive apoptosis and enhanced NFκB and phosphorylated Akt depletion in MCL with combination bortezomib plus rituximab, a phase II trial of bortezomib-rituximab in patients with relapsed/refractory MCL is underway.
mantle cell lymphoma; proteasome inhibition; CD20; survival and death pathways; apoptosis