In human cancers, loss of PTEN, stabilization of HIF-1alpha and activation of Ras and AKT converge to increase the activity of a key regulator of glycolysis, 6-phosphofructo-2-kinase (PFKFB3). This enzyme synthesizes fructose 2,6-bisphosphate (F26BP) which is an activator of 6-phosphofructo-1-kinase, a key step of glycolysis. Previously, a weak competitive inhibitor of PFKFB3, 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO), was found to reduce the glucose metabolism and proliferation of cancer cells. We have synthesized 73 derivatives of 3PO and screened each compound for activity against recombinant PFKFB3. One small molecule, 1-(4-pyridinyl)-3-(2-quinolinyl)-2-propen-1-one (PFK15), was selected for further pre-clinical evaluation of its pharmacokinetic, anti-metabolic and anti-neoplastic properties in vitro and in vivo. We found that PFK15 causes a rapid induction of apoptosis in transformed cells, has adequate pharmacokinetic properties, suppresses the glucose uptake and growth of Lewis lung carcinomas in syngeneic mice and yields anti-tumor effects in three human xenograft models of cancer in athymic mice that are comparable to FDA-approved chemotherapeutic agents. As a result of this study, a synthetic derivative and formulation of PFK15 has undergone IND-enabling toxicology and safety studies. A phase I clinical trial of its efficacy in advanced cancer patients will initiate in 2013 and we anticipate that this new class of anti-metabolic agents will yield acceptable therapeutic indices and prove to be synergistic with agents that disrupt neoplastic signaling.

Activating mutations of Fibroblast growth factor receptor-3 (FGFR3) have been described in approximately 75% of low-grade papillary bladder tumors. In muscle invasive disease, FGFR3 mutations are found in 20% of tumors, but overexpression of FGFR3 is observed in about half of cases. Therefore, FGFR3 is a particularly promising target for therapy in bladder cancer. Up to now most drugs tested for inhibition of FGFR3 have been small molecule, multi-tyrosine kinase inhibitors. More recently, a specific inhibitory monoclonal antibody targeting FGFR3 (R3Mab) has been described and tested pre-clinically. In this study, we have evaluated mutation and expression status of FGFR3 in 19 urothelial cancer cell lines and a cohort of 170 American bladder cancer patients. We demonstrated inhibitory activity of R3Mab on tumor growth and corresponding cell signaling in three different orthotopic xenografts of bladder cancer. Our results provide the pre-clinical proof of principle necessary to translate FGFR3 inhibition with R3Mab into clinical trials in patients with bladder cancer.

Despite significant treatment advances over the past decade, metastatic gastrointestinal stromal tumor (GIST) remains largely incurable. Rare diseases, such as GIST, individually affect small groups of patients but collectively are estimated to affect 25-30 million people in the U.S. alone. Given the costs associated with the discovery, development and registration of new drugs, orphan diseases such as GIST are often not pursued by mainstream pharmaceutical companies. As a result, "drug repurposing" or "repositioning", has emerged as an alternative to the traditional drug development process. In this study we screened 796 FDA-approved drugs and found that two of these compounds, auranofin and fludarabine phosphate, effectively and selectively inhibited the proliferation of GISTs including imatinib-resistant cells. One of the most notable drug hits, auranofin (Ridaura®), an oral, gold-containing agent approved by the FDA in 1985 for the treatment of rheumatoid arthritis (RA), was found to inhibit thioredoxin reductase (TrxR) activity and induce reactive oxygen species (ROS) production, leading to dramatic inhibition of GIST cell growth and viability. Importantly, the anti-cancer activity associated with auranofin was independent of IM resistant status, but was closely related to the endogenous and inducible levels of ROS, therefore is prior to IM response. Coupled with the fact auranofin has an established safety profile in patients, these findings suggest for the first time that auranofin may have clinical benefit for GIST patients, particularly in those suffering from imatinib-resistant and recurrent forms of this disease.

Advanced renal cell carcinoma (RCC) is an invariably fatal cancer. Currently, small-molecule inhibitors that target cell-growth, angiogenesis, or nutrient-sensing pathways represent the primary pharmacological interventions for this disease, but these inhibitors only delay tumor progression and are not curative. The cytokine interferon (IFN)-γ showed the potential to provide lasting remission in several phase I/II trials for advanced RCC, but subsequent trials, including a multi-center phase III study using IFN-γ as a monotherapy for RCC, were less promising. Notably, these trials were designed to exploit the indirect immune-modulatory effects of IFN-γ, while its direct anti-tumor properties - including its ability to trigger programmed cell death in tumors - remain mostly untapped. Here, we show that the proteasome inhibitor bortezomib (PS-341, Velcade) sensitizes otherwise-resistant RCC cells to direct necrotic death by IFN-γ. Mechanistically, we demonstrate that bortezomib functions at least in part by inhibiting pro-survival NF-κB signaling. In the absence of this signal, IFN-γ triggers programmed necrosis (or 'necroptosis') dependent on the kinase RIP1. When taken together with the observation that NF-κB signaling is elevated in RCC, these results provide rationale for the combined use of IFN-γ and bortezomib in the treatment of metastatic RCC.

Activation of TNF-related apoptosis-inducing ligand receptor 2 (TRAILR2) can induce apoptosis in a variety of human cancer cell lines and xenografts, while lacking toxicity in normal cells. The natural ligand and agonistic antibodies show anti-tumor activity in preclinical models of cancer, and this had led to significant excitement in the clinical potential of these agents. Unfortunately, this optimism has been tempered by trial data that, thus far, is not showing clear signs of efficacy in cancer patients. The reasons for discrepant preclinical and clinical observations are not understood, but one possibility is that the current TRAILR2 agonists lack sufficient potency to achieve a meaningful response in patients. Toward addressing that possibility, we have developed multivalent forms of a new binding scaffold (Tn3) that are superagonists of TRAILR2 and can induce apoptosis in tumor cell lines at subpicomolar concentrations. The monomer Tn3 unit was a fibronectin type III domain engineered for high affinity TRAILR2 binding. Multivalent presentation of this basic unit induced cell death in TRAILR2-expressing cell lines. Optimization of binding affinity, molecular format and valency contributed to cumulative enhancements of agonistic activity. An optimized multivalent agonist consisting of 8 tandem Tn3 repeats was highly potent in triggering cell death in TRAIL-sensitive cell lines and was 1-2 orders of magnitude more potent than TRAIL. Enhanced potency was also observed in vivo in a tumor xenograft setting. The TRAILR2 superagonists described here have the potential for superior clinical activity in settings insensitive to the current therapeutic agonists which target this pathway.

Inhibitors of the MAPKs, BRAF and MEK, induce tumor regression in the majority of patients with BRAF-mutant metastatic melanoma. The clinical benefit of MAPK inhibitors is restricted by the development of acquired resistance with half of those who benefit having progressed by 6-7 months and long-term responders uncommon. There remains no agreed treatment strategy on disease progression in these patients. Without published evidence, fears of accelerated disease progression on inhibitor withdrawal have led to the continuation of drugs beyond formal disease progression. We now demonstrate that treatment with MAPK inhibitors beyond disease progression can provide significant clinical benefit, and the withdrawal of these inhibitors led to a marked increase in the rate of disease progression in two patients. We also show that MAPK inhibitors retain partial activity in acquired resistant melanoma by examining drug-resistant clones generated to dabrafenib, trametinib or the combination of these drugs. All resistant sublines displayed a markedly slower rate of proliferation when exposed to MAPK inhibitors, and this coincided with a reduction in MAPK signalling, decrease in BrdU incorporation and S-phase inhibition. This cytostatic effect was also associated with diminished levels of cyclin D1 and p-pRb. Two short-term melanoma cultures generated from resistant tumour biopsies also responded to MAPK inhibition with comparable inhibitory changes in proliferation and MAPK signalling. These data provide a rationale for the continuation of BRAF and MEK inhibitors after disease progression and support the development of clinical trials to examine this strategy.

Phospho-sulindac (PS) is a sulindac derivative with promising anticancer activity in lung cancer, but its limited metabolic stability presents a major challenge for systemic therapy. We reasoned that inhalation delivery of PS might overcome first-pass metabolism and produce high levels of intact drug in lung tumors. Here, we developed a system for aerosolization of PS and evaluated the antitumor efficacy of inhaled PS in an orthotopic model of human non-small cell lung cancer (A549 cells). We found that administration by inhalation delivered high levels of PS to the lungs and minimized its hydrolysis to less active metabolites. Consequently, inhaled PS (6.5mg/kg) was highly effective in inhibiting lung tumorigenesis (75%, p<0.01) and significantly improved the survival of mice bearing orthotopic A549 xenografts. Mechanistically, PS suppressed lung tumorigenesis by 1) inhibiting EGFR activation, leading to profound inhibition of Raf/MEK/ERK and PI3K/AKT/mTOR survival cascades; 2) inducing oxidative stress, which provokes the collapse of mitochondrial membrane potential and mitochondria-dependent cell death; and 3) inducing autophagic cell death. Our data establish that inhalation delivery of PS is an efficacious approach to the prevention of lung cancer, which merits further evaluation.

Insulin-like growth factor receptor-1 (IGF-1R) inhibition could be a relevant therapeutic approach in small cell lung cancer (SCLC) given the importance of an IGF-1R autocrine loop and its role in DNA damage repair processes. We assessed IGF-1R and pAkt protein expression in 83 SCLC human specimens. The efficacy of R1507 (a monoclonal antibody directed against IGF-1R) alone or combined with cisplatin or ionizing radiation (IR) was evaluated in H69, H146 and H526 cells in vitro and in vivo. Innovative genomic and functional approaches were conducted to analyze the molecular behavior under the different treatment conditions. A total of 53% and 37% of human specimens expressed IGF-1R and pAkt, respectively. R1507 demonstrated single agent activity in H146 and H526 cells but not in H69 cells. R1507 exhibited synergistic effects with both Cisplatin and IR in vitro. The triple combination R1507-Cisplatin-IR led to a dramatic delay in tumor growth compared to Cisplatin-IR in H526 cells. Analyzing the apparent absence of antitumoral effect of R1507 alone in vivo, we observed a transient reduction of IGF-1R staining intensity in vivo, concomitant to the activation of multiple cell surface receptors and intracellular proteins involved in proliferation, angiogenesis and survival. Finally, we identified that the nucleotide excision repair pathway (NER) was mediated after exposure to R1507-CDDP and R1507-IR in vitro and in vivo. In conclusion, adding R1507 to the current standard Cisplatin-IR doublet reveals remarkable chemo- and radiosensitizing effects in selected SCLC models and warrants to be investigated in the clinical setting.

Metastatic prostate cancer has limited therapeutic options and has remained a major clinical challenge. Historically, prostate cancer has been widely recognized as a chemotherapy-resistant disease. However, clinical studies with anti-microtubule agents over the past decade have shown important efficacy in improving survival in patients with advanced disease. The favorable outcomes with microtubule-targeted agents have thus rekindled interest in such therapies for the clinical management of prostate cancer. Microtubules are dynamic polymers of tubulin molecules that play diverse roles within the cell. The dynamic property of microtubules is responsible for forming the bipolar mitotic apparatus, the mitotic spindle, that functions to precisely segregate the chromosomes during cell division. Thus, owing to the pivotal role that they play in the orchestration of mitotic events, microtubules provide excellent targets for anti-cancer therapy. Recent evidence also suggests that microtubules play a crucial role in the regulation of endocrine signaling pathways. Interestingly, microtubule-targeted agents such as taxanes not only inhibit cell division but also impair endocrine receptor signaling in prostate cancer. Herein, we provide an overview of the current status of microtubule-targeted therapies that are used in the treatment of prostate cancer and discuss novel mechanisms by which such therapies modulate endocrine signaling in prostate cancer. We also address the emerging roles of microtubule regulatory proteins in prostate carcinogenesis that could serve as attractive targets for prostate cancer therapy and might also serve as predictive biomarkers to identify patients who may benefit from endocrine and/or chemotherapy. This may have important implications in designing mechanism-based and targeted-therapeutic strategies for prostate cancer. Mol Cancer Ther; 12(5); 555-66. ©2013 AACR.