Enhanced radiosensitization of enzalutamide via schedule dependent administration to androgen-sensitive prostate cancer cells.

BACKGROUND: Prostate cancer (PCa) is a progressive disease and the most diagnosed cancer in men. The current standard of care for high-risk localized PCa is a combination of androgen deprivation therapy (ADT) and radiation (XRT). The majority of these patients however become resistant due to incomplete responses to ADT as a result of selective cells maintaining androgen receptor (AR) activity. Improvement can be made if increasing radiosensitivity is realized. Therefore, the aim of this study is to investigate the efficacy of the next-generation PCa drug Enzalutamide (ENZA), as a radiosensitizer in XRT therapy. METHODS: Using a number of androgen-dependent (LNCaP, PC3-T877A) and androgen-independent (C4-2, 22RV1, PC3, PC3-AR V7) cell lines, the effect of ENZA as a radiosensitizer was studied alone or in combination with ADT and/or XRT. Cell viability and cell survival were assessed, along with determination of cell cycle arrest, DNA damage response and repair, apoptosis and senescence. RESULTS: Our results indicated that either ENZA alone (in AR positive, androgen-dependent PCa cells) or in combination with ADT (in AR positive, hormone-insensitive PCa cells) potentiates radiation response [Dose enhancement factor (DEF) of 1.75 in LNCAP and 1.35 in C4-2] stronger than ADT + XRT conditions. Additionally, ENZA sensitized androgen dependent PCa cells to XRT in a schedule-dependent manner, where concurrent administration of ENZA and radiation lead to a maximal radiosensitization when compared to either drug administration prior or after XRT. In LNCaP cells, ENZA treatment significantly prolonged the presence of XRT-induced phospho-γH2AX up to 24 h after treatment; suggesting enhanced DNA damage. It also significantly increased XRT-induced apoptosis and senescence. CONCLUSIONS: Our data indicates that ENZA acts as a much stronger radiosensitizer compared to ADT. We have also observed that its efficacy is schedule dependent and related to increased levels of DNA damage and a delay of DNA repair processes. Finally, the initial abrogation of DNA-PKcs activity by AR inhibition and its subsequent recovery might represent an important mechanism by which PCa cells acquire resistance to combined anti-androgen and XRT treatment. This work suggests a new use of ENZA in combination with XRT that could be applicable in clinical trial settings for patients with early and intermediate hormone responsive disease.

Translation efficiency driven by CNOT3 subunit of the CCR4-NOT complex promotes leukemogenesis.

Protein synthesis is frequently deregulated during tumorigenesis. However, the precise contexts of selective translational control and the regulators of such mechanisms in cancer is poorly understood. Here, we uncovered CNOT3, a subunit of the CCR4-NOT complex, as an essential modulator of translation in myeloid leukemia. Elevated CNOT3 expression correlates with unfavorable outcomes in patients with acute myeloid leukemia (AML). CNOT3 depletion induces differentiation and apoptosis and delayed leukemogenesis. Transcriptomic and proteomic profiling uncovers c-MYC as a critical downstream target which is translationally regulated by CNOT3. Global analysis of mRNA features demonstrates that CNOT3 selectively influences expression of target genes in a codon usage dependent manner. Furthermore, CNOT3 associates with the protein network largely consisting of ribosomal proteins and translation elongation factors in leukemia cells. Overall, our work elicits the direct requirement for translation efficiency in tumorigenesis and propose targeting the post-transcriptional circuitry via CNOT3 as a therapeutic vulnerability in AML.

miR-148a-3p and DDX6 functional link promotes survival of myeloid leukemia cells.

Regulation of gene expression at the RNA level is an important regulatory mechanism in cancer. However, posttranscriptional molecular pathways underlying tumorigenesis remain largely unexplored. In this study, we uncovered a functional axis consisting of microRNA (miR)-148a-3p, RNA helicase DDX6, and its downstream target thioredoxin-interacting protein (TXNIP) in acute myeloid leukemia (AML). Using a DROSHA-knockout cell system to evaluate miR-mediated gene expression control, we comprehensively profiled putative transcripts regulated by miR-148a-3p and identified DDX6 as a direct target of miR-148a-3p in AML cells. DDX6 depletion induced cell cycle arrest, apoptosis, and differentiation, although delaying leukemia development in vivo. Genome-wide assessment of DDX6-binding transcripts and gene expression profiling of DDX6-depleted cells revealed TXNIP, a tumor suppressor, as the functional downstream target of DDX6. Overall, our study identified DDX6 as a posttranscriptional regulator that is required for AML survival. We proposed the regulatory link between miR-148a-3p and DDX6 as a potential therapeutic target in leukemia.

Identification of a Radiosensitivity Molecular Signature Induced by Enzalutamide in Hormone-sensitive and Hormone-resistant Prostate Cancer Cells.

Prostate cancer (PCa) is the most common cancer amongst men. A novel androgen receptor (AR) antagonist, enzalutamide (ENZA) has recently been demonstrated to enhance the effect of radiation (XRT) by impairing the DNA damage repair process. This study aimed to identify a radiosensitive gene signature induced by ENZA in the PCa cells and to elucidate the biological pathways which influence this radiosensitivity. We treated LNCaP (AR-positive, hormone-sensitive PCa cells) and C4-2 (AR-positive, hormone-resistant PCa cells) cells with ENZA alone and in combination with androgen deprivation therapy (ADT) and XRT. Using one-way ANOVA on the gene expression profiling, we observed significantly differentially expressed (DE) genes in inflammation-and metabolism-related genes in hormone-sensitive and hormone-resistant PCa cell lines respectively. Survival analysis in both the TCGA PRAD and GSE25136 datasets suggested an association between the expression of these genes and time to recurrence. These results indicated that ENZA alone or in combination with ADT enhanced the effect of XRT through immune and inflammation-related pathways in LNCaP cells and metabolic-related pathways in C4-2 cells. Kaplan-Meier analysis and Cox proportional hazard models showed that low expression of all the candidate genes except for PTPRN2 were associated with tumor progression and recurrence in a PCa cohort.