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A reciprocal role of prostate cancer on stromal DNA damage.

ABSTRACT: DNA damage found in prostate cancer-associated fibroblasts (CAF) promotes tumor progression. In the absence of somatic mutations in CAF, epigenetic changes dictate how stromal coevolution is mediated in tumors. Seventy percent of prostate cancer patients lose expression of transforming growth factor-beta type II receptor (TGFBR2) in the stromal compartment (n=77, P-value=0.0001), similar to the rate of glutathione S-transferase P1 (GSTP1) silencing. Xenografting of human prostate cancer epithelia, LNCaP, resulted in the epigenetic Tgfbr2 silencing of host mouse prostatic fibroblasts. Stromal Tgfbr2 promoter hypermethylation, initiated by LNCaP cells, was found to be dependent on interleukin 6 expression, based on neutralizing antibody studies. We further found that pharmacologic and transgenic knockout of TGF-? responsiveness in prostatic fibroblasts induced Gstp1 promoter methylation. It is known that TGF-? promotes DNA stability, however, the mechanism is not well understood. Both prostatic human CAF and mouse transgenic knockout of Tgbr2 had elevated DNA methyltransferase I (DNMT1) activity and histone H3 lysine 9 trimethylation (H3K9me3) to suggest greater promoter methylation. Interestingly, the conditional knockout of Tgfbr2 in mouse prostatic fibroblasts, in modeling epigenetic silencing of Tgfbr2, had greater epigenetic gene silencing of multiple DNA damage repair and oxidative stress response genes, based on promoter methylation array analysis. Homologous gene silencing was validated by reverse transcriptase (RT)-PCR in mouse and human prostatic CAF. Not surprisingly, DNA damage repair gene silencing in the prostatic stromal cells corresponded with the presence of DNA damage. Restoring the expression of the epigenetically silenced genes in wild-type fibroblasts with radiation-induced DNA damage reduced tumor progression. Tumor progression was inhibited even when epigenetic silencing was reversed in the Tgfbr2-knockout prostatic fibroblasts. Taken together, fibroblastic epigenetic changes causative of DNA damage, initiated by association with cancer epithelia, is a dominant mediator of tumor progression over TGF-? responsiveness.

SUBMITTER: Banerjee J

PROVIDER: S-EPMC4121379 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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A reciprocal role of prostate cancer on stromal DNA damage.

Banerjee J J Mishra R R Li X X Jackson R S RS Sharma A A Bhowmick N A NA

Oncogene 20131021 41

DNA damage found in prostate cancer-associated fibroblasts (CAF) promotes tumor progression. In the absence of somatic mutations in CAF, epigenetic changes dictate how stromal coevolution is mediated in tumors. Seventy percent of prostate cancer patients lose expression of transforming growth factor-beta type II receptor (TGFBR2) in the stromal compartment (n=77, P-value=0.0001), similar to the rate of glutathione S-transferase P1 (GSTP1) silencing. Xenografting of human prostate cancer epitheli ...[more]

PMID: 24141771

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Project description:Steroid hormone signaling induces vast gene expression programs which necessitate the local formation of transcription factories at regulatory regions and large-scale alterations of the genome architecture to allow communication among distantly related cis-acting regions. This involves major stress at the genomic DNA level. Transcriptionally active regions are generally instable and prone to breakage due to the torsional stress and local depletion of nucleosomes that make DNA more accessible to damaging agents. A dedicated DNA damage response (DDR) is therefore essential to maintain genome integrity at these exposed regions. The DDR is a complex network involving DNA damage sensor proteins, such as the poly(ADP-ribose) polymerase 1 (PARP-1), the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), the ataxia-telangiectasia-mutated (ATM) kinase and the ATM and Rad3-related (ATR) kinase, as central regulators. The tight interplay between the DDR and steroid hormone receptors has been unraveled recently. Several DNA repair factors interact with the androgen and estrogen receptors and support their transcriptional functions. Conversely, both receptors directly control the expression of agents involved in the DDR. Impaired DDR is also exploited by tumors to acquire advantageous mutations. Cancer cells often harbor germline or somatic alterations in DDR genes, and their association with disease outcome and treatment response led to intensive efforts towards identifying selective inhibitors targeting the major players in this process. The PARP-1 inhibitors are now approved for ovarian, breast, and prostate cancer with specific genomic alterations. Additional DDR-targeting agents are being evaluated in clinical studies either as single agents or in combination with treatments eliciting DNA damage (e.g., radiation therapy, including targeted radiotherapy, and chemotherapy) or addressing targets involved in maintenance of genome integrity. Recent preclinical and clinical findings made in addressing DNA repair dysfunction in hormone-dependent and -independent prostate and breast tumors are presented. Importantly, the combination of anti-hormonal therapy with DDR inhibition or with radiation has the potential to enhance efficacy but still needs further investigation.

Project description:IntroductionWe previously reported that cholesterol homeostasis in prostate cancer (PC) is regulated by 27-hydroxycholesterol (27HC) and that CYP27A1, the enzyme that converts cholesterol to 27HC, is frequently lost in PCs. We observed that restoring the CYP27A1/27HC axis inhibited PC growth. In this study, we investigated the mechanism of 27HC-mediated anti-PC effects.MethodsWe employed in vitro models and human transcriptomics data to investigate 27HC mechanism of action in PC. LNCaP (AR+) and DU145 (AR-) cells were treated with 27HC or vehicle. Transcriptome profiling was performed using the Affymetrix GeneChip™ microarray system. Differential expression was determined, and gene set enrichment analysis was done using the GSEA software with hallmark gene sets from MSigDB. Key changes were validated at mRNA and protein levels. Human PC transcriptomes from six datasets were analyzed to determine the correlation between CYP27A1 and DNA repair gene expression signatures. DNA damage was assessed via comet assays.ResultsTranscriptome analysis revealed 27HC treatment downregulated Hallmark pathways related to DNA damage repair, decreased expression of FEN1 and RAD51, and induced "BRCAness" by downregulating genes involved in homologous recombination regulation in LNCaP cells. Consistently, we found a correlation between higher CYP27A1 expression (i.e., higher intracellular 27HC) and decreased expression of DNA repair gene signatures in castration-sensitive PC (CSPC) in human PC datasets. However, such correlation was less clear in metastatic castration-resistant PC (mCRPC). 27HC increased expression of DNA damage repair markers in PC cells, notably in AR+ cells, but no consistent effects in AR- cells and decreased expression in non-neoplastic prostate epithelial cells. While testing the clinical implications of this, we noted that 27HC treatment increased DNA damage in LNCaP cells via comet assays. Effects were reversible by adding back cholesterol, but not androgens. Finally, in combination with olaparib, a PARP inhibitor, we showed additive DNA damage effects.DiscussionThese results suggest 27HC induces "BRCAness", a functional state thought to increase sensitivity to PARP inhibitors, and leads to increased DNA damage, especially in CSPC. Given the emerging appreciation that defective DNA damage repair can drive PC growth, future studies are needed to test whether 27HC creates a synthetic lethality to PARP inhibitors and DNA damaging agents in CSPC.

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A reciprocal role of prostate cancer on stromal DNA damage.

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A reciprocal role of prostate cancer on stromal DNA damage.

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