Androgen receptor splice variants drive castration-resistant prostate cancer metastasis by activating distinct transcriptional programs.

One critical mechanism through which prostate cancer (PCa) adapts to treatments targeting androgen receptor (AR) signaling is the emergence of ligand-binding domain-truncated and constitutively active AR splice variants, particularly AR-V7. While AR-V7 has been intensively studied, its ability to activate distinct biological functions compared to the full-length AR (AR-FL), and its role in regulating the metastatic progression of castration-resistant PCa (CRPC), remains unclear. Our study found that, under castrated conditions, AR-V7 strongly induced osteoblastic bone lesions, a response not observed with AR-FL overexpression. Through combined ChIP-seq, ATAC-seq, and RNA-seq analyses, we demonstrated that AR-V7 uniquely accesses the androgen-responsive elements in compact chromatin regions, activating a distinct transcription program. This program was highly enriched for genes involved in epithelial-mesenchymal transition and metastasis. Notably, we discovered that SOX9, a critical metastasis driver gene, was a direct target and downstream effector of AR-V7. Its protein expression was dramatically upregulated in AR-V7-induced bone lesions. Moreover, we found that Ser81 phosphorylation enhanced AR-V7's pro-metastasis function by selectively altering its specific transcription program. Blocking this phosphorylation with CDK9 inhibitors impaired the AR-V7-mediated metastasis program. Overall, our study has provided molecular insights into the role of AR splice variants in driving the metastatic progression of CRPC.

Demethylation of EHMT1/GLP Protein Reprograms Its Transcriptional Activity and Promotes Prostate Cancer Progression.

Epigenetic reprogramming, mediated by genomic alterations and dysregulation of histone reader and writer proteins, plays a critical role in driving prostate cancer progression and treatment resistance. However, the specific function and regulation of EHMT1 (also known as GLP) and EHMT2 (also known as G9A), well-known histone 3 lysine 9 methyltransferases, in prostate cancer progression remain poorly understood. Through comprehensive investigations, we discovered that both EHMT1 and EHMT2 proteins have the ability to activate oncogenic transcription programs in prostate cancer cells. Silencing EHMT1/2 or targeting their enzymatic activity with small-molecule inhibitors can markedly decrease prostate cancer cell proliferation and metastasis in vitro and in vivo. In-depth analysis of posttranslational modifications of EHMT1 protein revealed the presence of methylation at lysine 450 and 451 residues in multiple prostate cancer models. Notably, we found that lysine 450 can be demethylated by LSD1. Strikingly, concurrent demethylation of both lysine residues resulted in a rapid and profound expansion of EHMT1's chromatin binding capacity, enabling EHMT1 to reprogram the transcription networks in prostate cancer cells and activate oncogenic signaling pathways. Overall, our studies provide valuable molecular insights into the activity and function of EHMT proteins during prostate cancer progression. Moreover, we propose that the dual-lysine demethylation of EHMT1 acts as a critical molecular switch, triggering the induction of oncogenic transcriptional reprogramming in prostate cancer cells. These findings highlight the potential of targeting EHMT1/2 and their demethylation processes as promising therapeutic strategies for combating prostate cancer progression and overcoming treatment resistance. Significance: In this study, we demonstrate that EHMT1 and EHMT2 proteins drive prostate cancer development by transcriptionally activating multiple oncogenic pathways. Mechanistically, the chromatin binding of EHMT1 is significantly expanded through demethylation of both lysine 450 and 451 residues, which can serve as a critical molecular switch to induce oncogenic transcriptional reprogramming in prostate cancer cells.

SETD7 functions as a transcription repressor in prostate cancer via methylating FOXA1.

Dysregulation of histone lysine methyltransferases and demethylases is one of the major mechanisms driving the epigenetic reprogramming of transcriptional networks in castration-resistant prostate cancer (CRPC). In addition to their canonical histone targets, some of these factors can modify critical transcription factors, further impacting oncogenic transcription programs. Our recent report demonstrated that LSD1 can demethylate the lysine 270 of FOXA1 in prostate cancer (PCa) cells, leading to the stabilization of FOXA1 chromatin binding. This process enhances the activities of the androgen receptor and other transcription factors that rely on FOXA1 as a pioneer factor. However, the identity of the methyltransferase responsible for FOXA1 methylation and negative regulation of the FOXA1-LSD1 oncogenic axis remains unknown. SETD7 was initially identified as a transcriptional activator through its methylation of histone 3 lysine 4, but its function as a methyltransferase on nonhistone substrates remains poorly understood, particularly in the context of PCa progression. In this study, we reveal that SETD7 primarily acts as a transcriptional repressor in CRPC cells by functioning as the major methyltransferase targeting FOXA1-K270. This methylation disrupts FOXA1-mediated transcription. Consistent with its molecular function, we found that SETD7 confers tumor suppressor activity in PCa cells. Moreover, loss of SETD7 expression is significantly associated with PCa progression and tumor aggressiveness. Overall, our study provides mechanistic insights into the tumor-suppressive and transcriptional repression activities of SETD7 in mediating PCa progression and therapy resistance.

Susceptibility-Associated Genetic Variation in NEDD9 Contributes to Prostate Cancer Initiation and Progression.

Although American men of European ancestry represent the largest population of patients with prostate cancer, men of African ancestry are disproportionately affected by prostate cancer, with higher prevalence and worse outcomes. These racial disparities in prostate cancer are due to multiple factors, but variations in genomic susceptibility such as SNP may play an important role in determining cancer aggressiveness and treatment outcome. Using public databases, we have identified a prostate cancer susceptibility SNP at an intronic enhancer of the neural precursor expressed, developmentally downregulated 9 (NEDD9) gene, which is strongly associated with increased risk of patients with African ancestry. This genetic variation increased expression of NEDD9 by modulating the chromatin binding of certain transcription factors, including ERG and NANOG. Moreover, NEDD9 displayed oncogenic activity in prostate cancer cells, promoting prostate cancer tumor growth and metastasis in vitro and in vivo. Together, our study provides novel insights into the genetic mechanisms driving prostate cancer racial disparities. SIGNIFICANCE: A prostate cancer susceptibility genetic variation in NEDD9, which is strongly associated with the increased risk of patients with African ancestry, increases NEDD9 expression and promotes initiation and progression of prostate cancer.See related commentary by Mavura and Huang, p. 3764.

A new and improved algorithm for the quantification of chromatin condensation from microscopic data shows decreased chromatin condensation in regenerating axolotl limb cells.

The nuclear landscape plays an important role in the regulation of tissue and positional specific genes in embryonic and developing cells. Changes in this landscape can be dynamic, and are associated with the differentiation of cells during embryogenesis, and the de-differentiation of cells during induced pluripotent stem cell (iPSC) formation and in many cancers. However, tools to quantitatively characterize these changes are limited, especially in the in vivo context, where numerous tissue types are present and cells are arranged in multiple layers. Previous tools have been optimized for the monolayer nature of cultured cells. Therefore, we present a new algorithm to quantify the condensation of chromatin in two in vivo systems. We first developed this algorithm to quantify changes in chromatin compaction and validated it in differentiating spermatids in zebrafish testes. Our algorithm successfully detected the typical increase in chromatin compaction as these cells differentiate. We then employed the algorithm to quantify the changes that occur in amphibian limb cells as they participate in a regenerative response. We observed that the chromatin in the limb cells de-compacts as they contribute to the regenerating organ. We present this new tool as an open sourced software that can be readily accessed and optimized to quantify chromatin compaction in complex multi-layered samples.

Minibrain and Wings apart control organ growth and tissue patterning through down-regulation of Capicua.

The transcriptional repressor Capicua (Cic) controls tissue patterning and restricts organ growth, and has been recently implicated in several cancers. Cic has emerged as a primary sensor of signaling downstream of the receptor tyrosine kinase (RTK)/extracellular signal-regulated kinase (ERK) pathway, but how Cic activity is regulated in different cellular contexts remains poorly understood. We found that the kinase Minibrain (Mnb, ortholog of mammalian DYRK1A), acting through the adaptor protein Wings apart (Wap), physically interacts with and phosphorylates the Cic protein. Mnb and Wap inhibit Cic function by limiting its transcriptional repressor activity. Down-regulation of Cic by Mnb/Wap is necessary for promoting the growth of multiple organs, including the wings, eyes, and the brain, and for proper tissue patterning in the wing. We have thus uncovered a previously unknown mechanism of down-regulation of Cic activity by Mnb and Wap, which operates independently from the ERK-mediated control of Cic. Therefore, Cic functions as an integrator of upstream signals that are essential for tissue patterning and organ growth. Finally, because DYRK1A and CIC exhibit, respectively, prooncogenic vs. tumor suppressor activities in human oligodendroglioma, our results raise the possibility that DYRK1A may also down-regulate CIC in human cells.

The sys-1 and sys-3 genes cooperate with Wnt signaling to establish the proximal-distal axis of the Caenorhabditis elegans gonad.

To form the proximal-distal axis of the C. elegans gonad, two somatic gonadal precursor cells, Z1 and Z4, divide asymmetrically to generate one daughter with a proximal fate and one with a distal fate. Genes governing this process include the lin-17 frizzled receptor, wrm-1/beta-catenin, the pop-1/TCF transcription factor, lit-1/nemo-like kinase, and the sys-1 gene. Normally, all of these regulators promote the distal fate. Here we show that nuclear levels of a pop-1 GFP fusion protein are less abundant in the distal than in the proximal Z1/Z4 daughters. This POP-1 asymmetry is lost in mutants disrupting Wnt/MAPK regulation, but retained in sys-1 mutants. We find that sys-1 is haplo-insufficient for gonadogenesis defects and that sys-1 and pop-1 mutants display a strong genetic interaction in double heterozygotes. Therefore, sys-1 is a dose-sensitive locus and may function together with pop-1 to control Z1/Z4 asymmetry. To identify other regulatory genes in this process, we screened for mutants resembling sys-1. Four such genes were identified (gon-14, -15, -16, and sys-3) and shown to interact genetically with sys-1. However, only sys-3 promotes the distal fate at the expense of the proximal fate. We suggest that sys-3 is a new key gene in this pathway and that gon-14, gon-15, and gon-16 may cooperate with POP-1 and SYS-1 at multiple stages of gonad development.

POP-1 controls axis formation during early gonadogenesis in C. elegans.

The shape and polarity of the C. elegans gonad is defined during early gonadogenesis by two somatic gonadal precursor cells, Z1 and Z4, and their descendants. Z1 and Z4 divide asymmetrically to establish the proximal-distal axes of the gonad and to generate regulatory leader cells that control organ shape. In this paper, we report that pop-1, the C. elegans TCF/LEF-1 transcription factor, controls the first Z1/Z4 asymmetric division and hence controls proximal-distal axis formation. We have identified two pop-1(Sys) alleles (for symmetrical sisters) that render the Z1/Z4 divisions symmetrical. The pop-1(q645) allele is fully penetrant for the Sys gonadogenesis defect in hermaphrodites, but affects male gonads weakly; pop-1(q645) alters a conserved amino acid in the beta-catenin binding domain. The pop-1(q624) allele is weakly penetrant for multiple defects and appears to be a partial loss-of-function mutation; pop-1(q624) alters a conserved amino acid in the HMG-box DNA binding domain. Zygotic pop-1(RNAi) confirms the role of pop-1 in Z1/Z4 asymmetry and reveals additional roles of pop-1, including one in leader cell migration. Two other Wnt pathway regulators, wrm-1 and lit-1, have the same effect as pop-1 on Z1/Z4 asymmetry. Therefore, wrm-1 and lit-1 are required for pop-1 function, rather than opposing it as observed in the early embryo. We conclude that POP-1 controls the Z1/Z4 asymmetric division and thereby establishes the proximal-distal axes of the gonad. This control over proximal-distal polarity extends our view of Wnt signaling in C. elegans, which had previously been known to control anterior-posterior polarities.