Effects of HDM2 antagonism on sunitinib resistance, p53 activation, SDF-1 induction, and tumor infiltration by CD11b+/Gr-1+ myeloid derived suppressor cells.

BACKGROUND: The studies reported herein were undertaken to determine if the angiostatic function of p53 could be exploited as an adjunct to VEGF-targeted therapy in the treatment of renal cell carcinoma (RCC). METHODS: Nude/beige mice bearing human RCC xenografts were treated with various combinations of sunitinib and the HDM2 antagonist MI-319. Tumors were excised at various time points before and during treatment and analyzed by western blot and IHC for evidence of p53 activation and function. RESULTS: Sunitinib treatment increased p53 levels in RCC xenografts and transiently induced the expression of p21(waf1), Noxa, and HDM2, the levels of which subsequently declined to baseline (or undetectable) with the emergence of sunitinib resistance. The development of resistance and the suppression of p53-dependent gene expression temporally correlated with the induction of the p53 antagonist HDMX. The concurrent administration of MI-319 markedly increased the antitumor and anti-angiogenic activities of sunitinib and led to sustained p53-dependent gene expression. It also suppressed the expression of the chemokine SDF-1 (CXCL12) and the influx of CD11b+/Gr-1+ myeloid-derived suppressor cells (MDSC) otherwise induced by sunitinib. Although p53 knockdown markedly reduced the production of the angiostatic peptide endostatin, the production of endostatin was not augmented by MI-319 treatment. CONCLUSIONS: The evasion of p53 function (possibly through the expression of HDMX) is an essential element in the development of resistance to VEGF-targeted therapy in RCC. The maintenance of p53 function through the concurrent administration of an HDM2 antagonist is an effective means of delaying or preventing the development of resistance.

Differential modulatory effects of GSK-3ß and HDM2 on sorafenib-induced AIF nuclear translocation (programmed necrosis) in melanoma.

BACKGROUND: GSK-3ß phosphorylates numerous substrates that govern cell survival. It phosphorylates p53, for example, and induces its nuclear export, HDM2-dependent ubiquitination, and proteasomal degradation. GSK-3ß can either enhance or inhibit programmed cell death, depending on the nature of the pro-apoptotic stimulus. We previously showed that the multikinase inhibitor sorafenib activated GSK-3ß and that this activation attenuated the cytotoxic effects of the drug in various BRAF-mutant melanoma cell lines. In this report, we describe the results of studies exploring the effects of GSK-3ß on the cytotoxicity and antitumor activity of sorafenib combined with the HDM2 antagonist MI-319. RESULTS: MI-319 alone increased p53 levels and p53-dependent gene expression in melanoma cells but did not induce programmed cell death. Its cytotoxicity, however, was augmented in some melanoma cell lines by the addition of sorafenib. In responsive cell lines, the MI-319/sorafenib combination induced the disappearance of p53 from the nucleus, the down modulation of Bcl-2 and Bcl-xL, the translocation of p53 to the mitochondria and that of AIF to the nuclei. These events were all GSK-3ß-dependent in that they were blocked with a GSK-3ß shRNA and facilitated in otherwise unresponsive melanoma cell lines by the introduction of a constitutively active form of the kinase (GSK-3ß-S9A). These modulatory effects of GSK-3ß on the activities of the sorafenib/MI-319 combination were the exact reverse of its effects on the activities of sorafenib alone, which induced the down modulation of Bcl-2 and Bcl-xL and the nuclear translocation of AIF only in cells in which GSK-3ß activity was either down modulated or constitutively low. In A375 xenografts, the antitumor effects of sorafenib and MI-319 were additive and associated with the down modulation of Bcl-2 and Bcl-xL, the nuclear translocation of AIF, and increased suppression of tumor angiogenesis. CONCLUSIONS: Our data demonstrate a complex partnership between GSK-3ß and HDM2 in the regulation of p53 function in the nucleus and mitochondria. The data suggest that the ability of sorafenib to activate GSK-3ß and alter the intracellular distribution of p53 may be exploitable as an adjunct to agents that prevent the HDM2-dependent degradation of p53 in the treatment of melanoma.

The Raf inhibitor BAY 43-9006 (Sorafenib) induces caspase-independent apoptosis in melanoma cells.

Mitogen-activated protein kinase (MAPK) is activated in the majority of melanomas, and its activity is essential for cell survival. In this report, we examined the effects of a novel raf inhibitor BAY 43-9006 on melanoma cell viability and intracellular signaling and found that it induces apoptosis through a caspase-independent mechanism. At concentrations that suppress extracellular signal-regulated kinase (ERK) phosphorylation, BAY 43-9006 dephosphorylates Bad on Ser(75) and Ser(99), activates Bak and Bax, and reduces the mitochondrial transmembrane potential. BAY 43-9006 (sorafenib) down-modulates the levels of Bcl-2 and Bcl-X(L) in a MAPK-independent manner in A2058 and SKMEL5 melanoma cells but not in the more resistant A375 cells. Of the three lines tested, only A375 cells were rescued from BAY 43-9006-induced apoptosis by knocking down Bad. BAY 43-9006 induced poly(ADP-ribose) polymerase cleavage and the mitochondrial release of cytochrome c and SMAC. However, the pan-caspase inhibitor Z-VAD-fmk had only a modest protective effect against the drug, suggesting that BAY 43-9006-induced apoptosis is largely caspase independent. BAY 43-9006 but not the MAP/ERK kinase inhibitors PD98059 or U0126 induced the nuclear translocation of apoptosis-inducing factor (AIF) in A2058 and SKMEL5 cells, and the introduction of a small interfering RNA (siRNA) for AIF partially protected these cells from BAY 43-9006-induced apoptosis. The AIF siRNA had little effect in A375 cells, in which drug-induced AIF release was negligible. These data indicate that in sensitive cell lines, BAY 43-9006-induced apoptosis is independent of Bad dephosphorylation and caspase activation and largely mediated through the nuclear translocation of AIF.

Circulating BRAFV600E Levels Correlate with Treatment in Patients with Thyroid Carcinoma.

BACKGROUND: BRAFV600E is the most common mutation in papillary thyroid carcinoma (PTC) and can be associated with aggressive disease. Previously, a highly sensitive blood RNA-based BRAFV600E assay was reported. The objective of this study was to assess the correlation of BRAFV600E circulating tumor RNA levels with surgical and medical treatment. METHODS: Circulating BRAFV600E levels were assessed in (i) a murine model of undifferentiated (anaplastic) thyroid carcinoma with known BRAFV600E mutation undergoing BRAFV600E-inhibitor (BRAFi) treatment, and (ii) in 111 patients enrolled prior to thyroidectomy (n = 86) or treatment of advanced recurrent or metastatic PTC (n = 25). Blood samples were drawn for BRAFV600E analysis before and after treatment. Testing characteristics were assessed and positivity criteria optimized. Changes in blood BRAFV600E values were assessed and compared to clinical characteristics and response to therapy. RESULTS: In a murine model of anaplastic thyroid carcinoma with BRAFV600E mutation, blood BRAFV600E RNA correlated with tumor volume in animals treated with BRAFi. In tissue BRAFV600E-positive (n = 36) patients undergoing initial surgery for PTC, blood BRAFV600E levels declined postoperatively (median 370.0-178.5 fg/ng; p = 0.002). In four patients with metastatic or poorly differentiated thyroid carcinoma receiving targeted therapies, blood BRAFV600E declined following therapy and corresponded with radiographic evidence of partial response or stable disease. CONCLUSIONS: This study shows the correlation of blood BRAFV600E levels in response to treatment in both an established animal model of thyroid cancer and in patients with BRAFV600E-positive tumors with all stages of disease. This assay represents an alternative biomarker in patients with positive thyroglobulin antibodies, and tumors, which do not express thyroglobulin.

Targeting the mitogen-activated protein kinase pathway in the treatment of malignant melanoma.

The mitogen-activated protein kinase (MAPK; i.e., Ras-Raf-Erk) pathway is an attractive target for therapeutic intervention in melanoma due to its integral role in the regulation of proliferation, invasiveness, and survival and the recent availability of pharmaceutical agents that inhibit the various kinases and GTPases that comprise the pathway. Genetic studies have identified activating mutations in either B-raf or N-ras in most cutaneous melanomas. Other studies have delineated the contribution of autocrine growth factors (e.g., hepatocyte growth factor and fibroblast growth factor) to MAPK activation in melanoma. Still, others have emphasized the consequences of the down-modulation of endogenous raf inhibitors, such as Sprouty family members (e.g., SPRY2) and raf-1 kinase inhibitory protein, in the regulation of the pathway. The diversity of molecular mechanisms used by melanoma cells to ensure the activity of the MAPK pathway attests to its importance in the evolution of the disease and the likelihood that inhibitors of the pathway may prove to be highly effective in melanoma treatment. MAPK inhibition has been shown to result in the dephosphorylation of the proapoptotic Bcl-2 family members Bad and Bim. This process in turn leads to caspase activation and, ultimately, the demise of melanoma cells through the induction of apoptosis. Several recent studies have identified non-mitogen-activated protein/extracellular signal-regulated kinase kinase-binding partners of raf and suggested that the prosurvival effects of raf and the lethality of raf inhibition are mediated through these alternative targets, independent of the MAPK pathway. Other studies have suggested that endothelial cells are the primary targets of raf inhibitors in vivo and that the antitumor effect of these agents are largely attributable to angiogenesis inhibition. This article reviews the genetic and biochemical factors contributing to MAPK activation in melanoma, the mechanisms by which inhibition of the pathway might prove deleterious to tumor cells, and the potential of MAPK inhibitors in the treatment of the disease.

FCGR Polymorphisms Influence Response to IL2 in Metastatic Renal Cell Carcinoma.

Purpose: Fc-gamma receptors (FCGRs) are expressed on immune cells, bind to antibodies, and trigger antibody-induced cell-mediated antitumor responses when tumor-reactive antibodies are present. The affinity of the FCGR/antibody interaction is variable and dependent upon FCGR polymorphisms. Prior studies of patients with cancer treated with immunotherapy indicate that FCGR polymorphisms can influence antitumor response for certain immunotherapies that act via therapeutically administered mAbs or via endogenous tumor-reactive antibodies induced from tumor antigen vaccines. The previously published "SELECT" trial of high-dose aldesleukin (HD-IL2) for metastatic renal cell carcinoma resulted in an objective response rate of 25%. We evaluated the patients in this SELECT trial to determine whether higher-affinity FCGR polymorphisms are associated with outcome.Experimental Design: SNPs in FCGR2A, FCGR3A, and FCGR2C were analyzed, individually and in combination, for associations between genotype and clinical outcome.Results: When higher-affinity genotypes for FCGR2A, FCGR3A, and FCGR2C were considered together, they were associated with significantly increased tumor shrinkage and prolonged survival in response to HD-IL2.Conclusions: Although associations of higher-affinity FCGR genotype with clinical outcome have been demonstrated with mAb therapy and with idiotype vaccines, to our knowledge, this is the first study to show associations of FCGR genotypes with outcome following HD-IL2 treatment. We hypothesize that endogenous antitumor antibodies may engage immune cells through their FCGRs, and HD-IL2 may enhance antibody-induced tumor destruction, or antibody-enhanced tumor antigen presentation, via augmented activation of innate or adaptive immune responses; this FCGR-mediated immune activity would be augmented through immunologically favorable FCGRs. Clin Cancer Res; 23(9); 2159-68. ©2016 AACR.

Novel drugs that target the metabolic reprogramming in renal cell cancer.

Molecular profiling studies of tumor tissue from patients with clear cell renal cell cancer (ccRCC) have revealed extensive metabolic reprogramming in this disease. Associations were found between metabolic reprogramming, histopathologic Fuhrman grade, and overall survival of patients. Large-scale genomics, proteomics, and metabolomic analyses have been performed to identify the molecular players in this process. Genes involved in glycolysis, the pentose phosphate pathway, glutamine metabolism, and lipogenesis were found to be upregulated in renal cell cancer (RCC) specimens as compared to normal tissue. Preclinical research indicates that mutations in VHL, FBP1, and the PI3K-AKT-mTOR pathway drives aerobic glycolysis through transcriptional activation of the hypoxia-inducible factors (HIF). Mechanistic studies revealed glutamine as an important source for de novo fatty acid synthesis through reductive carboxylation. Amplification of MYC drives reductive carboxylation. In this review, we present a detailed overview of the metabolic changes in RCC in conjunction with potential novel therapeutics. We discuss preclinical studies that have investigated targeted agents that interfere with various aspects of tumor cell metabolism and emphasize their impact specifically on glycolysis, lipogenesis, and tumor growth. Furthermore, we describe a number of phase 1 and 2 clinical trials that have been conducted with these agents.

Detection of Circulating BRAF(V600E) in Patients with Papillary Thyroid Carcinoma.

BRAF(V600E) is a common mutation in papillary thyroid carcinoma (PTC) correlated with aggressive features. Our objective was to assess the feasibility and accuracy of a novel RNA-based blood assay to identify individuals with a high-risk tumor mutation in patients with PTC. Patients with benign or malignant thyroid disorders were included between September 2013 and July 2014 before either thyroidectomy (n = 62) or treatment of recurrent or metastatic PTC (n = 8). RNA was isolated from peripheral blood lymphocytes and reverse transcribed and followed by two rounds of nested PCR amplification with a restriction digest specific for wild-type BRAF. BRAF(V600E) levels were quantified with standardization curves. Circulating BRAF(V600E) levels were compared with BRAF mutation status from surgical pathologic DNA-based tissue assays. Testing characteristics and receiving-operator curve using tissue results as the gold standard were assessed. Matched blood and tissue assays for BRAF(V600E) were performed on 70 patients with PTC (stages I to IV, n = 48) or other (n = 22) thyroid tumors. Sixty-three percent of PTC patients tested positive for BRAF(V600E) with conventional tissue assays on surgical specimens. The correlation between the RNA-based blood assay and tissue BRAF status was 0.71. PTC patients harbor detectable BRAF(V600E) circulating tumor cells. This blood assay is feasible and has potential as a biomarker for prognosis, surveillance, clinical decision making, and assessment of treatment response to BRAF-targeted therapies.

Dramatic Response of BRAF V600E Mutant Papillary Craniopharyngioma to Targeted Therapy.

We recently reported that BRAF V600E is the principal oncogenic driver of papillary craniopharyngioma, a highly morbid intracranial tumor commonly refractory to treatment. Here, we describe our treatment of a man age 39 years with multiply recurrent BRAF V600E craniopharyngioma using dabrafenib (150mg, orally twice daily) and trametinib (2mg, orally twice daily). After 35 days of treatment, tumor volume was reduced by 85%. Mutations that commonly mediate resistance to MAPK pathway inhibition were not detected in a post-treatment sample by whole exome sequencing. A blood-based BRAF V600E assay detected circulating BRAF V600E in the patient's blood. Re-evaluation of the existing management paradigms for craniopharyngioma is warranted, as patient morbidity might be reduced by noninvasive mutation testing and neoadjuvant-targeted treatment.

Clinical, Molecular, and Immune Analysis of Dabrafenib-Trametinib Combination Treatment for BRAF Inhibitor-Refractory Metastatic Melanoma: A Phase 2 Clinical Trial.

IMPORTANCE: Combined treatment with dabrafenib and trametinib (CombiDT) achieves clinical responses in only about 15% of patients with BRAF inhibitor (BRAFi)-refractory metastatic melanoma in contrast to the higher response rate observed in BRAFi-naïve patients. Identifying correlates of response and mechanisms of resistance in this population will facilitate clinical management and rational therapeutic development. OBJECTIVE: To determine correlates of benefit from CombiDT therapy in patients with BRAFi-refractory metastatic melanoma. DESIGN, SETTING, AND PARTICIPANTS: Single-center, single-arm, open-label phase 2 trial of CombiDT treatment in patients with BRAF V600 metastatic melanoma resistant to BRAFi monotherapy conducted between September 2012 and October 2014 at the University of Texas MD Anderson Cancer Center. Key eligibility criteria for participants included BRAF V600 metastatic melanoma, prior BRAFi monotherapy, measurable disease (RECIST 1.1), and tumor accessible for biopsy. INTERVENTIONS: Patients were treated with dabrafenib (150 mg, twice daily) and trametinib (2 mg/d) continuously until disease progression or intolerance. All participants underwent a mandatory baseline biopsy, and optional biopsy specimens were obtained on treatment and at disease progression. Whole-exome sequencing, reverse transcription polymerase chain reaction analysis for BRAF splicing, RNA sequencing, and immunohistochemical analysis were performed on tumor samples, and blood was analyzed for levels of circulating BRAF V600. MAIN OUTCOMES AND MEASURES: The primary end point was overall response rate (ORR). Progression-free survival (PFS) and overall survival (OS) were secondary clinical end points. RESULTS: A total of 28 patients were screened, and 23 enrolled. Among evaluable patients, the confirmed ORR was 10%; disease control rate (DCR) was 45%, and median PFS was 13 weeks. Clinical benefit was associated with duration of prior BRAFi therapy greater than 6 months (DCR, 73% vs 11% for ≤6 months; P = .02) and decrease in circulating BRAF V600 at day 8 of cycle 1 (DCR, 75% vs 18% for no decrease; P = .02) but not with pretreatment mitogen-activated protein kinase (MAPK) pathway mutations or activation. Biopsy specimens obtained during treatment demonstrated that CombiDT therapy failed to achieve significant MAPK pathway inhibition or immune infiltration in most patients. CONCLUSIONS AND RELEVANCE: The baseline presence of MAPK pathway alterations was not associated with benefit from CombiDT in patients with BRAFi-refractory metastatic melanoma. Failure to inhibit the MAPK pathway provides a likely explanation for the limited clinical benefit of CombiDT in this setting. Circulating BRAF V600 is a promising early biomarker of clinical response. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01619774.

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.

Assaying for BRAF V600E in tissue and blood in melanoma.

The Braf(V600E) mutation has been detected in patients with metastatic melanoma, colon, thyroid, and other cancers. Studies suggested that tumors with this mutation are especially sensitive to BRAF inhibitors-hence the need to reliably determine the BRAF status of tumor specimens. The present technologies used to screen for this mutation fail to address the problems associated with infiltrating stromal and immune cells bearing wild-type BRAF alleles and thus may fail to detect the presence of mutant BRAF(V600E) tumors. We have developed a rapid, inexpensive method of BRAF analysis that reduces the contamination of wild-type BRAF sequences from tumor biopsies. The protocol involves a series of PCR amplifications and restriction digestions that take advantage of unique features of both wild-type and mutant BRAF RNA at codon 600. Using this protocol, mutant BRAF can be detected in RNA from mixed populations with as few as 0.1 % BRAF(V600E) mutant containing cells.

Clinical utility of a blood-based BRAF(V600E) mutation assay in melanoma.

BRAF inhibitors (BRAFi) have led to clinical benefit in patients with melanoma. The development of a blood-based assay to detect and quantify BRAF levels in these patients has diagnostic, prognostic, and predictive capabilities that could guide treatment decisions. Blood BRAF(V600E) detection and quantification were performed on samples from 128 patients with stage II (19), III (67), and IV (42) melanoma. Tissue BRAF analysis was performed in all patients with stage IV disease and in selected patients with stage II and III disease. Clinical outcomes were correlated to initial BRAF levels as well as BRAF level dynamics. Serial analysis was performed on 17 stage IV melanoma patients treated with BRAFi and compared with tumor measurements by RECIST. The assay was highly sensitive (96%) and specific (95%) in the stage IV setting, using a blood level of 4.8 pg as "positive." BRAF levels typically decreased following BRAFi. A subset of these patients (5) had an increase in BRAF(V600E) values 42 to 112 days before clinical or radiographic disease progression (PD). From 86 patients with resected, stage II or III melanoma, 39 had evidence of disease relapse (45.3%). Furthermore, BRAF mutation in the blood after surgical resection in these patients was not associated with a difference in relapse risk, although tissue BRAF status was only available for a subset of patients. In summary, we have developed a highly sensitive and specific, blood-based assay to detect BRAF(V600) mutation in patients with melanoma.

Clinical profiling of BCL-2 family members in the setting of BRAF inhibition offers a rationale for targeting de novo resistance using BH3 mimetics.

While response rates to BRAF inhibitiors (BRAFi) are high, disease progression emerges quickly. One strategy to delay the onset of resistance is to target anti-apoptotic proteins such as BCL-2, known to be associated with a poor prognosis. We analyzed BCL-2 family member expression levels of 34 samples from 17 patients collected before and 10 to 14 days after treatment initiation with either vemurafenib or dabrafenib/trametinib combination. The observed changes in mRNA and protein levels with BRAFi treatment led us to hypothesize that combining BRAFi with a BCL-2 inhibitor (the BH3-mimetic navitoclax) would improve outcome. We tested this hypothesis in cell lines and in mice. Pretreatment mRNA levels of BCL-2 negatively correlated with maximal tumor regression. Early increases in mRNA levels were seen in BIM, BCL-XL, BID and BCL2-W, as were decreases in MCL-1 and BCL2A. No significant changes were observed with BCL-2. Using reverse phase protein array (RPPA), significant increases in protein levels were found in BIM and BID. No changes in mRNA or protein correlated with response. Concurrent BRAF (PLX4720) and BCL2 (navitoclax) inhibition synergistically reduced viability in BRAF mutant cell lines and correlated with down-modulation of MCL-1 and BIM induction after PLX4720 treatment. In xenograft models, navitoclax enhanced the efficacy of PLX4720. The combination of a selective BRAF inhibitor with a BH3-mimetic promises to be an important therapeutic strategy capable of enhancing the clinical efficacy of BRAF inhibition in many patients that might otherwise succumb quickly to de novo resistance. Trial registrations: ClinicalTrials.gov NCT01006980; ClinicalTrials.gov NCT01107418; ClinicalTrials.gov NCT01264380; ClinicalTrials.gov NCT01248936; ClinicalTrials.gov NCT00949702; ClinicalTrials.gov NCT01072175.

An inexpensive, specific and highly sensitive protocol to detect the BrafV600E mutation in melanoma tumor biopsies and blood.

The Braf(V600E) mutation has been detected in patients with metastatic melanoma, colon, thyroid and other cancers. Recent studies suggested that tumors with this mutation are especially sensitive to Braf inhibitors, hence the need to reliably determine the Braf status of tumor specimens. The present technologies used to screen for this mutation fail to address the problems associated with infiltrating stromal and immune cells bearing wild-type Braf alleles and thus may fail to detect the presence of mutant Braf(V600E) tumors. We have developed a rapid, inexpensive method that reduces the contamination of wild-type Braf sequences from tumor biopsies. The protocol involves a series of PCR amplifications and restriction digestions that take advantage of unique features of both wild type and mutant Braf RNA at position 600. Using this protocol, mutant Braf can be detected in RNA from mixed populations with as few as 0.1% Braf(V600E) mutant cells.

The efficacy of the novel dual PI3-kinase/mTOR inhibitor NVP-BEZ235 compared with rapamycin in renal cell carcinoma.

PURPOSE: Inhibitors of TORC1 have been shown to be active in patients with metastatic renal cell carcinoma (RCC). As the phosphatidylinositol 3-kinase (PI3K) pathway activates numerous other kinases, transcription factors, and proteins associated with cell growth and survival besides mammalian target of rapamycin (mTOR), disruption of this pathway upstream of mTOR may be more effective than inhibition of TORC1 alone. EXPERIMENTAL DESIGN: To investigate this possibility, the dual PI3K/mTOR inhibitor NVP-BEZ235 was compared with rapamycin in RCC cell lines and xenografts generated from 786-O and A498 cells. RESULTS: Treatment of RCC cell lines with NVP-BEZ235 in vitro resulted in the nuclear translocation of p27, greater reduction in tumor cell proliferation, and more complete suppression of Akt, Mnk-1, eIF4E, and 4EBP-1 phosphorylation and cyclin D1 and hypoxia-inducible factor 2alpha (HIF2alpha) expression than that achieved with rapamycin. The reduction of HIF2alpha levels correlated with reduced HIF activity as determined by luciferase assay. NVP-BEZ235 induced growth arrest in both the 786-O and A498 xenografts that was associated with inhibition of Akt and S6 phosphorylation as well as the induction of apoptosis and reduction in markers of tumor cell proliferation. In contrast, rapamycin induced only minimal growth retardation. CONCLUSION: Dual inhibition of PI3K/mTOR with NVP-BEZ235 induced growth arrest in RCC cell lines both in vitro and in vivo more effectively than inhibition of TORC1 alone. These results provide the rationale for the clinical assessment of agents such as NVP-BEZ235 in patients with advanced RCC.