Steen, Travis Van der

Abstract Fatty acid synthase (FASN) is a novel therapeutic target for cancer as it has increased expression in many different types of cancers. There has been significant understanding that cancer cells can hijack and modify tightly regulated metabolic pathway for its own survival. FASN is the enzyme that synthesizes palmitate from malonyl-CoA for energy storage, structure and biomolecules. FASN expression is low to undetectable in normal cells with the exception of liver and adipose tissue. In this study, we investigated the role of FASN in breast cancer cells. We observed that in highly expressing FASN breast cancer cells, TVB-3166, FASN inhibitor, results in a decrease in cellular proliferation and an increase in cellular death. FASN inhibition increased reactive oxygen species (ROS) and altered NADPH/NADP+ ratio. Increase in ROS and NADPH have been linked to the intrinsic apoptosis pathway. Additionally, there is an increase in expression of the BH3-only proteins Bim, Puma and Noxa, leading to the permeabilization of the mitochondria and the release of cytochrome c. Furthermore, after prolong exposure to TVB-3166 a number of cells enter into a senescent state. This was observed the in detection of β-galactosidase and confirmed by the expression of senescent markers including ARF, INK4A, and CIP. Additionally, when the cells were treated with a CDK4/6 inhibitor in combination with the FASN inhibitor TVB-3166, an increase in stress induced premature senescence was observed. Our data demonstrates that inhibition of FASN induces intrinsic apoptosis while it stimulates cellular senescence to the apoptotic resistant cells. Therefore, the ability for TVB-3166 to both eradicate and overturn cell growth makes it potential therapeutic modality. Citation Format: Travis Van der Steen, George Kemble, Ruth Lupu. Targeting fatty acid synthase induces apoptosis and senescence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 708.

Abstract Reactivation of the androgen receptor (AR) is the hallmark of prostate cancer (PCa) progression to the castration resistant prostate cancer (CRPC) phenotype. Currently, treatment for CRPC strives to impede the full-length AR (AR-FL) from becoming activated through targeting the ligand binding domain (LBD) via androgen deprivation therapy or treatment with antiandrogens. However, these options can give rise to AR-variants (AR-Vs) that lack the LBD and are unresponsive to treatment. Therefore, targeting the N-terminus of AR, which is conserved between AR-FL and AR-Vs, is critical for identifying new treatment options. Phosphorylation of serine 81 (AR-pS81) in the N-terminus of AR is critical for AR activation, stability and recruitment to the chromatin. Similar phosphorylation sites can be observed in the N-terminus of both AR-FL and AR-Vs. Expression of Pin1, a proline isomerase, exhibits a strong correlation with progression and relapse of PCa. Also, suppression of Pin1 in PCa decreases cell proliferation rates, suggesting that Pin1 may play a pivotal role in PCa progression. Pin1 isomerizes proline residues from trans to cis when the adjacent serine/threonine residue is phosphorylated. Dephosphorylation by phosphatases occurs when a pS-P motif is in the trans conformation. Therefore, Pin1 isomerization of AR pS81-P82 from trans to cis could prevent dephosphorylation and result in constitutive or enhanced AR activity. Stable cell lines with Pin1 knockdown were generated via shRNA targeting the 5′ UTR of Pin1 that express either AR-FL and/or AR-Vs. Pin1 knockdown was confirmed by western blots, and AR activity was monitored by expression of several AR regulated genes. Additionally, AR recruitment to chromatin was assayed by ChIP and Re-Chip. Loss of Pin1 resulted in a 60% reduction of endogenous PSA expression, and AR was unable to induce PSA expression when treated with androgens. However, suppression of AR activity was not due to decreased recruitment of AR to chromatin. Phosphorylation of AR-pS81 was decreased by loss of Pin1, while protein stability and mRNA expression was not altered. These data suggest that Pin1 may play a critical role in regulating the transcriptional activity of AR by altering the accessibility of AR to interact with transcriptional machinery needed to maintain AR activity. (Funding for this project was provided by the T.J. Martell Foundation). Citation Format: Travis Van der Steen, Haojie Huang, Donald Tindall. Pin1 suppresses androgen receptor activity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 89. doi:10.1158/1538-7445.AM2015-89

The androgen receptor (AR) is important in the development of the prostate by regulating transcription, cellular proliferation, and apoptosis. AR undergoes posttranslational modifications that alter its transcription activity, translocation to the nucleus and stability. The posttranslational modifications that regulate these events are of utmost importance to understand the functional role of AR and its activity. The majority of these modifications occur in the activation function-1 (AF1) region of the AR, which contains the transcriptional activation unit 1 (TAU1) and 5 (TAU5). Identification of the modifications that occur to these regions may increase our understanding of AR activation in prostate cancer and the role of AR in the progression from androgen-dependent to castration-resistant prostate cancer (CRPC). Most of the posttranslational modifications identified to date have been determined using the full-length AR in androgen dependent cells. Further investigations into the role of posttranslational modifications in androgen-independent activation of full-length AR and constitutively active splicing variants are warranted, findings from which may provide new therapeutic options for CRPC.