Druggable Enzymes Research Articles

Abstract IA28: New targeted approaches for high-risk pediatric malignancies

Abstract While significant progress has been made in treating many pediatric malignancies, cancer remains the leading cause of death from disease in children. A number of childhood cancer subtypes remain particularly recalcitrant to dose-intensified cytotoxic treatment suggesting that new approaches are needed. Initial optimism that massively parallel sequencing efforts would reveal imminently targetable lesions has been tempered by a major finding that pediatric cancers often have simple genomes. While a signature mutation is frequently present, the product is often considered a difficult drug target, such as an aberrant transcription factor. Thus, the hope that cancer can be treated with combinations of drugs targeting specific gene mutations is unlikely to be imminently viable for most pediatric cancers. We hypothesized that while there is a notable paucity of events in easily druggable enzymes, a small number of sentinel lesions in an otherwise quiet genome may enable the discovery of synthetic lethal relationships with these key genetic events. Thus, we are applying unbiased approaches to identify key dependencies in pediatric cancers using functional genomic screening (shRNA and CRISPR) and chemical genomic screening. The primary goal is to connect key genetic lesions or disease lineages to new gene targets or small-molecule perturbations in the highest risk subtypes of pediatric cancers. Illustrative examples of our early findings will be presented. Citation Format: Kimberly Stegmaier. New targeted approaches for high-risk pediatric malignancies. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr IA28.

Abstract IA13: Deconvoluting the molecular circuitry of cancerous cells with high-throughput experimentation

Abstract Developmentally important signal transduction pathways such as those controlled by the secreted Wnt and Hedgehog (Hh) ligands are frequently exploited in cancerous cells to promote unfettered growth. We describe functional and chemical genomics-based efforts to recover actionable mechanisms sustaining cancer-associated Wnt and Hh signaling. Our findings extend the portfolio of druggable enzymes with anti-cancer relevance and reveal novel prosurvival mechanisms in cancerous cells. Citation Format: Lawrence Lum. Deconvoluting the molecular circuitry of cancerous cells with high-throughput experimentation. [abstract]. In: Proceedings of the AACR Special Conference on Translation of the Cancer Genome; Feb 7-9, 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 1):Abstract nr IA13.

Targeted inhibition of metastatic melanoma through interference with Pin1-FOXM1 signaling.

Melanoma is the most lethal form of skin cancer and successful treatment of metastatic melanoma remains challenging. BRAF/MEK inhibitors only show a temporary benefit due to rapid occurrence of resistance, whereas immunotherapy is mainly effective in selected subsets of patients. Thus, there is a need to identify new targets to improve treatment of metastatic melanoma. To this extent, we searched for markers that are elevated in melanoma and are under regulation of potentially druggable enzymes. Here, we show that the pro-proliferative transcription factor FOXM1 is elevated and activated in malignant melanoma. FOXM1 activity correlated with expression of the enzyme Pin1, which we found to be indicative of a poor prognosis. In functional experiments, Pin1 proved to be a main regulator of FOXM1 activity through MEK-dependent physical regulation during the cell cycle. The Pin1-FOXM1 interaction was enhanced by BRAFV600E, the driver oncogene in the majority of melanomas, and in extrapolation of the correlation data, interference with\\ Pin1 in BRAFV600E-driven metastatic melanoma cells impaired both FOXM1 activity and cell survival. Importantly, cell-permeable Pin1-FOXM1-blocking peptides repressed the proliferation of melanoma cells in freshly isolated human metastatic melanoma ex vivo and in three-dimensional-cultured patient-derived melanoids. When combined with the BRAFV600E-inhibitor PLX4032 a robust repression in melanoid viability was obtained, establishing preclinical value of patient-derived melanoids for prognostic use of drug sensitivity and further underscoring the beneficial effect of Pin1-FOXM1 inhibitory peptides as anti-melanoma drugs. These proof-of-concept results provide a starting point for development of therapeutic Pin1-FOXM1 inhibitors to target metastatic melanoma.

Abstract IA32: Targeting cancer cell dependencies on developmental signal transduction pathways

Abstract Developmentally important signal transduction pathways such as those controlled by the secreted Wnt and Hedgehog (Hh) ligands are frequently exploited in cancerous cells to promote unfettered growth. We describe functional and chemical genomics-based efforts to recover actionable mechanisms sustaining cancer-associated Wnt and Hh signaling. We discuss chemically tractable strategies for disrupting the fatty acylation of Wnt proteins and unanticipated vulnerabilities in Hh signaling to inhibitors of the Bcl-2 antiapoptotic proteins. Our findings extend the portfolio of druggable enzymes with anti-cancer relevance and reveal novel compensatory prosurvival mechanisms in cancerous cells that incorporate developmental pathway components. Citation Format: Lawrence Lum. Targeting cancer cell dependencies on developmental signal transduction pathways. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr IA32.

Prevent protein interactions to prevent cancer metastasis

Traditional drug design and discovery focus on inhibition of many so-called druggable enzyme activities, channels and cell surface receptors by targeting well-defined active sites. It has been grad...

Abstract 2238: Modeling local network connectivity to identify druggable enzyme targets.

Abstract While targeted therapies have provided extended lifespans to some cancer patients, the majority of cancers do not have these “golden bullet” therapies despite their increasing need. To address this, large-scale drug screening efforts are conducted to identify novel therapeutic targets in various cancers. While these screening efforts identify important nodes in the cancer cell signaling network, they do not necessarily reflect the “druggability” of those nodes. We predict that the local molecular connections surrounding a drug target will be predictive of inhibitor efficacy and should be considered in drug screening efforts and prioritizing drugs for clinical development. Towards this end, we have used computational modeling to survey the behavior of a three-tiered enzyme cascade configured with all possible one- and two-feedback interactions. To characterize the effect of local network topology on pathway inhibition, we compared inhibition by RNAi vs. small-molecules in the computational models. Our modeling predicts that certain topologies will be more sensitive to RNAi than small-molecules, and that other topologies will show the opposite behavior. We next experimentally tested one network wiring that our modeling predicts will be more potently inhibited by a small-molecule inhibitor than RNAi inhibition, where the third enzyme in the cascade negatively feeds back on the first. This topology is found in the Raf-MEK1/2-ERK1/2 pathway where ERK1/2 can hyperphosphorylate and inactivate Raf, creating a negative feedback loop. To test our model hypothesis, we compared the potency of shMEK constructs relative to equivalent inhibition by a small-molecule inhibitor of MEK1/2, U0126. We analyzed pathway output (pERK1/2) over time in response to pathway activation. Our data suggests that pERK1/2 responses are both qualitatively and quantitatively different for cells inhibited by shMEK compared to U0126. In U0126-treated cells, pERK1/2 activation after stimulation is delayed and transient compared to shMEK1/2 cells, which show reduced pERK1/2 compared to controls but no differences in signaling kinetics. We further investigated the phenotypic response from this difference in pERK1/2 signaling and found that upon stimulation the shMEK-inhibited cells proliferated whereas the U0126-inhibited cells did not. These results support our model prediction that small-molecule inhibition of MEK1/2 will more potently inhibit pathway output compared to RNAi. While global loss-of-function screens can identify new targets for therapy, it is critical to determine whether drugging such targets will yield the same outcome as eliminating them. Our work demonstrates the need to consider local network topology in drug screening and target identification for drug development. Prioritizing targets for drug development in this way will reduce the cost of drug development and allow more effective therapies to reach patients in the clinic. Citation Format: Karin J. Jensen, Christian B. Moyer, Kevin A. Janes. Modeling local network connectivity to identify druggable enzyme targets. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2238. doi:10.1158/1538-7445.AM2013-2238