Rupal S. Bhatt

A Mouse Serine/Threonine Kinase Homologous to C. elegans UNC51 Functions in Parallel Fiber Formation of Cerebellar Granule Neurons

The formation of the cerebellar circuitry depends on the outgrowth of connections between the two principal classes of neurons, granule neurons and Purkinje neurons. To identify genes that function in axon outgrowth, we have isolated a mouse homolog of C. elegans UNC51, which is required for axon formation, and tested its function in cerebellar granule neurons. Murine Unc51.1 encodes a novel serine/threonine kinase and is expressed in granule cells in the cerebellar cortex. Retroviral infection of immature granule cells with a dominant negative Unc51.1 results in inhibition of neurite outgrowth in vitro and in vivo. Moreover, infected neurons fail to express TAG-1 or neuron-specific beta-tubulin, suggesting that development is arrested prior to this initial step of differentiation. Thus, Unc51.1 signals the program of gene expression leading to the formation of granule cell axons.

Differential expression of PD-L1 between primary and metastatic sites in clear cell Renal Cell Carcinoma

Response to PD-L1 inhibition depends on its expression. Primary ccRCC tumors and their matching metastases were compared, and because PD-L1 was mostly in high nuclear-grade areas, these should be specifically selected for assessment to limit false negatives. PD-L1 expression in primary clear-cell renal cell carcinoma (ccRCC) increases the likelihood of response to anti–PD-1 inhibition, but fails to identify all responders. We hypothesized that PD-L1 levels assessed in randomly selected areas of the primary tumors may not accurately reflect expression levels in metastatic lesions, which are the target of systemic therapy. Therefore, we compared PD-L1 expression in a series of primary ccRCC and their metastases. Tissue blocks from 53 primary ccRCCs and 76 corresponding metastases were retrieved. Areas with predominant and highest nuclear grade were selected. Slides were immunostained with a validated anti–PD-L1 antibody (405.9A11). Membranous expression in tumor cells was quantified using H-score. Expression in tumor-infiltrating mononuclear cells (TIMC) was quantified using a combined score. Discordant tumor cell PD-L1 staining between primary tumors and metastases was observed in 11 of 53 cases (20.8%). Overall, tumor cell PD-L1 levels were not different in primary tumors and metastases (P = 0.51). Tumor cell PD-L1 positivity was associated with higher T stage (P = 0.03) and higher Fuhrman nuclear grade (P < 0.01). Within individual lesions, PD-L1 positivity was heterogeneous and almost exclusively detected in high nuclear grade areas (P < 0.001). No difference was found in PD-L1 levels in TIMCs between primary tumors and metastases (P = 0.82). The heterogeneity of PD-L1 expression in ccRCC suggests that its assessment as a predictive biomarker for PD-1 blockade may require analysis of metastatic lesions. Notably, because PD-L1 expression was mostly detected in high nuclear grade areas, to avoid false-negative results, these areas should be specifically selected for assessment. Cancer Immunol Res; 3(10); 1158–64. ©2015 AACR.

Resistance of Renal Cell Carcinoma to Sorafenib Is Mediated by Potentially Reversible Gene Expression

Purpose Resistance to antiangiogenic therapy is an important clinical problem. We examined whether resistance occurs at least in part via reversible, physiologic changes in the tumor, or results solely from stable genetic changes in resistant tumor cells. Experimental Design Mice bearing two human RCC xenografts were treated with sorafenib until they acquired resistance. Resistant 786-O cells were harvested and reimplanted into naïve mice. Mice bearing resistant A498 cells were subjected to a 1 week treatment break. Sorafenib was then again administered to both sets of mice. Tumor growth patterns, gene expression, viability, blood vessel density, and perfusion were serially assessed in treated vs control mice. Results Despite prior resistance, reimplanted 786-O tumors maintained their ability to stabilize on sorafenib in sequential reimplantation steps. A transcriptome profile of the tumors revealed that the gene expression profile of tumors upon reimplantation reapproximated that of the untreated tumors and was distinct from tumors exhibiting resistance to sorafenib. In A498 tumors, revascularization was noted with resistance and cessation of sorafenib therapy and tumor perfusion was reduced and tumor cell necrosis enhanced with re-exposure to sorafenib. Conclusions In two RCC cell lines, resistance to sorafenib appears to be reversible. These results support the hypothesis that resistance to VEGF pathway therapy is not solely the result of a permanent genetic change in the tumor or selection of resistant clones, but rather is due to a great extent to reversible changes that likely occur in the tumor and/or its microenvironment.

The high-dose aldesleukin "select" trial: A trial to prospectively validate predictive models of response to treatment in patients with metastatic renal cell carcinoma

Purpose: High-dose aldesleukin (HD IL2) received FDA approval for the treatment of metastatic renal cell carcinoma (MRCC) in 1992, producing a 14% objective response rate (ORR) and durable remissions. Retrospective studies suggested that clinical and pathologic features could predict for benefit. The Cytokine Working Group conducted this prospective trial to validate proposed predictive markers of response to HD IL2. Experimental Design: Standard HD IL2 was administered to prospectively evaluate whether the ORR of patients with mRCC with “good” predictive pathologic features based on an “integrated selection” model [ISM (e.g., clear-cell histology subclassification and carbonic anhydrase-9 (CA-9) IHC staining] was significantly higher than the ORR of a historical, unselected population. Archived tumor was collected for pathologic analysis including tumor programmed death-ligand 1 (PD-L1) expression. Results: One hundred and twenty eligible patients were enrolled between June 11 and September 7; 70% were Memorial Sloan Kettering Cancer Center (New York, NY) intermediate risk, 96% had clear cell RCC, and 99% had prior nephrectomy. The independently assessed ORR was 25% (30/120, 95% CI, 17.5%–33.7%, P = 0.0014; 3 complete responses, 27 partial responses) and was higher than a historical ORR. Thirteen patients (11%) remained progression free at 3 years and the median overall survival was 42.8 months. ORR was not statistically different by ISM classification (“good-risk” 23% vs. “poor-risk” 30%; P = 0.39). ORR was positively associated with tumor PD-L1 expression (P = 0.01) by IHC. Conclusions: In this prospective, biomarker validation study, HD IL2 produced durable remissions and prolonged survival in both “good” and “poor-risk” patients. The proposed ISM was unable to improve the selection criteria. Novel markers (e.g., tumor PD L1 expression) appeared useful, but require independent validation. Clin Cancer Res; 21(3); 561–8. ©2014 AACR.

A phase 2 pilot trial of low-dose, continuous infusion, or "metronomic" paclitaxel and oral celecoxib in patients with metastatic melanoma.

Tumor angiogenesis has been associated with a poor prognosis in patients with metastatic melanoma (MM). Microtubule stabilizers and cyclooxygenase 2 (COX‐2) inhibitors, alone and in combination, have produced inhibitory effects on endothelial cells and tumor angiogenesis. Angiogenesis, which is the growth of new blood vessels, is necessary for tumor growth and progression. Thus, the authors tested the safety and efficacy of a low dose of paclitaxel and celecoxib in patients with MM.

Retrospective Analysis of the Safety and Efficacy of Interleukin-2 After Prior Vegf-targeted Therapy in Patients With Advanced Renal Cell Carcinoma

Agents targeting vascular endothelial growth factor (VEGF) signaling have been advocated as frontline therapy for advanced renal cancer. The role of interleukin 2 (IL-2) therapy after resistance to VEGF-targeted therapy remains unexplored. We conducted a retrospective analysis of the tolerability and efficacy of IL-2 therapy in patients who had previously received VEGF-targeted therapy. Twenty-three consecutive patients who received salvage IL-2 therapy were analyzed. Fifteen patients had received prior tyrosine kinase inhibitors (TKIs) (sorafenib or sunitinib), whereas 8 patients had received bevacizumab alone. Six of 23 patients did not receive week 2 of cycle 1 of treatment. All 6 of these patients had received prior TKIs. The incidence of severe cardiac toxicities, including 1 sudden cardiac death, in patients receiving prior TKI was 40% (95% confidence interval, 16.3-67.7%), significantly higher than what is expected from historical experience. Only 1 of 23 patients proceeded to receive a second cycle of IL-2. No patients achieved a partial or complete response to therapy. This retrospective analysis highlights unexpected and severe cardiac toxicities in patients receiving IL-2 after VEGF-targeted TKI therapy. The assumption that IL-2 therapy can be safely administered after TKI therapy may not be valid. Further examination of the safety of this sequential approach is necessary and more cautious patient selection seems warranted.

Renal Cancer Resistance to Antiangiogenic Therapy Is Delayed by Restoration of Angiostatic Signaling

Treatment of metastatic renal cell cancer (RCC) with antiangiogenic agents that block vascular endothelial growth factor (VEGF) receptor 2 signaling produces tumor regression in a substantial fraction of patients; however, resistance typically develops within 6 to 12 months. The purpose of this study was to identify molecular pathways involved in resistance. Treatment of mice bearing either 786-0 or A498 human RCC xenografts with sorafenib or sunitinib produced tumor growth stabilization followed by regrowth despite continued drug administration analogous to the clinical experience. Tumors and plasma were harvested at day 3 of therapy and at the time of resistance to assess pathways that may be involved in resistance. Serial perfusion imaging, and plasma and tumor collections were obtained in mice treated with either placebo or sunitinib alone or in combination with intratumoral injections of the angiostatic chemokine CXCL9. Sunitinib administration led to an early downmodulation of IFNγ levels as well as reduction of IFNγ receptor and downstream angiostatic chemokines CXCL9 to 11 within the tumor. Intratumoral injection of CXCL9, although producing minimal effects by itself, when combined with sunitinib resulted in delayed resistance in vivo accompanied by a prolonged reduction of microvascular density and tumor perfusion as measured by perfusion imaging relative to sunitinib alone. These results provide evidence that resistance to VEGF receptor therapy is due at least in part to resumption of angiogenesis in association with reduction of IFNγ-related angiostatic chemokines, and that this resistance can be delayed by concomitant administration of CXCL9. Mol Cancer Ther; 9(10); 2793–802. ©2010 AACR.

Angiotensin System Inhibitors and Survival Outcomes in Patients with Metastatic Renal Cell Carcinoma

Purpose: The renin-angiotensin system may play a role in carcinogenesis. The purpose of this study was to evaluate the impact of angiotensin system inhibitors (ASI) on outcomes in metastatic renal cell carcinoma (mRCC) patients treated in the targeted therapy era. Experimental Design: We conducted a pooled analysis of mRCC patients treated on phase II and III clinical trials. Statistical analyses were performed using Cox regression adjusted for several risk factors and the Kaplan–Meier method. Results: A total of 4,736 patients were included, of whom 1,487 received ASIs and 783 received other antihypertensive agents. Overall, ASI users demonstrated improved overall survival (OS) compared with users of other antihypertensive agents (adjusted HR, 0.838, P = 0.0105, 26.68 vs. 18.07 months) and individuals receiving no antihypertensive therapy (adjusted HR, 0.810, P = 0.0026, 26.68 vs. 16.72 months). When stratified by therapy type, a benefit in OS was demonstrated in ASI users compared with nonusers in individuals receiving VEGF therapy (adjusted HR, 0.737, P < 0.0001, 31.12 vs. 21.94 months) but not temsirolimus or IFNα. An in vitro cell viability assay demonstrated that sunitinib in combination with an ASI significantly decreased RCC cell viability compared with control at physiologically relevant doses. This effect was not observed with either agent alone or with other non-ASI antihypertensives or temsirolimus. Conclusions: In the largest analysis to date, we demonstrate that ASI use improved survival in mRCC patients treated in the targeted therapy era. Further studies are warranted to investigate the mechanism underlying this interaction and verify our observations to inform clinical practice. Clin Cancer Res; 21(11); 2471–9. ©2015 AACR.

Angiopoietin 2 Is a Potential Mediator of High-Dose Interleukin 2–Induced Vascular Leak

Purpose: High-dose interleukin 2 (HDIL2) produces durable tumor regressions in 10% of patients with metastatic renal cell carcinoma and melanoma. However, a major toxicity is vascular leak syndrome (VLS). We previously reported elevated serum angiopoietin 2 (Ang2) in septic patients with vascular leak and hypothesized that Ang2 might also contribute to HDIL2 VLS. Experimental Design: Blood was collected from 14 patients receiving HDIL2 and from 4 patients receiving HDIL2 and bevacizumab, an antibody against vascular endothelial growth factor (VEGF). The effect of Ang2 was studied in vitro by incubating high Ang2 patient serum with cultured endothelial cells. Results: Pretreatment Ang2 levels were in the reference range (median, 3.3 ng/mL) and rose with each day of IL-2 therapy (median peak, 29.7 ng/mL). No trend was seen in free VEGF levels during therapy. Patients treated with HDIL2 and bevacizumab all developed VLS and elevated Ang2. High Ang2 patient sera induced propermeability structural changes in endothelial cells, an effect reversed by blockade with the competitive ligand angiopoietin 1 (Ang1). Conclusions: Ang2 may be a mediator of HDIL2 VLS as evidenced by (a) an increase in Ang2 in all patients on HDIL2; (b) the effect of high Ang2 patient serum on cultured endothelial cells; (c) rescue of those structural changes by Ang1. The lack of correlation between VLS and serum VEGF levels in patients treated with HDIL2 alone or in combination with bevacizumab suggests that VEGF is not a major contributor to VLS or Ang2 release. These data suggest that the inhibition of Ang2 may mitigate VLS in patients receiving HDIL2.

Phase 2 study of neoadjuvant docetaxel plus bevacizumab in patients with high-risk localized prostate cancer: a Prostate Cancer Clinical Trials Consortium trial.

Treatment of high‐risk localized prostate cancer remains inadequate. The authors performed a phase 2 multicenter trial of neoadjuvant docetaxel plus bevacizumab before radical prostatectomy.