HOXB13 interaction with MEIS1 modifies proliferation and gene expression in prostate cancer

Abstract

Background The recurrent p.Gly84Glu germline mutation (G84E) in HOXB13 is consistently associated with prostate cancer (PCa), although the mechanisms underlying such linkage remain elusive. The majority of the PCa‐associated HOXB13 mutations identified are localized to two conserved domains in HOXB13 that have been shown to mediate the interaction with MEIS cofactors belonging to the TALE family of homeodomain transcription factors. In this study, we sought to interrogate the biochemical and functional interactions between HOXB13 and MEIS in prostatic cells with a goal of defining how the HOXB13‐MEIS complex impacts PCa pathobiology and define the extent to which the oncogenic activity of G84E is related to its effect on HOXB13‐MEIS interaction/function. Methods HOXB13 and MEIS paralog expression in prostate epithelial cells and PCa cell lines was characterized by qPCR and immunoblot analyses. HOXB13 and MEIS1 co‐expression in human prostate tissue was confirmed by IHC, followed by co‐IP mapping of HOXB13‐MEIS1 interactions. Proliferation of the PCa cell line LAPC4 following shRNA‐mediated knockdown of each gene or both genes was assessed using DNA‐ and metabolic‐based assays. Transcriptional targets of HOXB13 and MEIS1 were identified by gene expression profiling and qPCR. Finally, protein stability of HOXB13 in the context of MEIS1 was determined using pulse‐chase assays. Results HOXB13 and MEIS1 are co‐expressed and interact in prostate cells. Both of the putative MEIS interacting domains (MID) within HOXB13 were shown to be capable of mediating the interaction between HOXB13 and MEIS1 independently and such interactions were not influenced by the G84E mutation. The inhibitory effect of either HOXB13 or MEIS1 knockdown on cellular proliferation was augmented by knockdown of both genes, and MEIS1 knockdown abolished HOXB13‐driven regulation of BCHE and TNFSF10 mRNA expression. Notably, we demonstrated that MEIS1 stabilized the HOXB13 protein in LAPC4 cells. Conclusions Our study provides evidence for functional HOXB13‐MEIS1 interactions in PCa. MEIS1 may contribute to the cancer‐promoting actions of HOXB13 in cellular proliferation and gene regulation by prolonging HOXB13 half‐life. Our data demonstrates that G84E is not a loss‐of‐function mutation that interferes with HOXB13 stability or ability to interact with MEIS1.

MEIS-mediated suppression of human prostate cancer growth and metastasis through HOXB13-dependent regulation of proteoglycans

“…Further, the HOXB13 G84E mutation is associated with an increased odds ratio (OR) for colorectal cancer (OR: 2.8, p=0.02), bladder cancer (OR: 1.99, p=0.06), and leukemia (OR: 3.17, p=0.01), further demonstrating the importance of the need to understand how HOXB13 mutations promote cancer ( Akbari et al, 2013 ; Beebe-Dimmer et al, 2015 ). A recent study did not detect an effect of the G84E mutation on interaction with MEIS1 ( Johng et al, 2019 ), suggesting alternative mechanisms for HOXB13 mutations in driving prostate carcinogenesis beyond disruption of MEIS interaction. Thus, further research is needed to define the transcriptional impact of HOXB13 mutations on MEIS interaction and the regulation of MEIS–HOXB13-associated gene targets.…”

MEIS1 down-regulation by MYC mediates prostate cancer development through elevated HOXB13 expression and AR activity

“…We sought to examine the genetic contribution of MYC to the development and progression of primary PCa in the context of dysregulated growth by using anti-MYC immunohistochemistry and performing laser capture microdissection on populations of human prostate tumor cells with varying 6 expression of MYC protein. We show using transcriptome profiling that increased MYC activity is inversely correlated with expression of Myeloid Ecotropic viral Insertion Site 1 (MEIS1), a transcription factor that interacts with and regulates the activity of HOX homeodomain transcription factors, including HOXB13 [18][19][20]. We determined that MYC binding to the MEIS1 locus decreases as MYC levels increases, and that MEIS1 expression is negatively correlated with HOXB13 expression and AR activity.…”

“…Previously, Bhanvadia et al [19] reported that tumors with increased MEIS1 are potentially less aggressive, based on studies of LAPC-4 prostate cancer cells expressing shRNA against MEIS1 and that tumors with lower levels of MEIS1 were at greater risk of biochemical recurrence. HOXB13, a homeodomain transcription factor, has been shown to regulate AR activity while shRNA against HOXB13 in LAPC4 cells inhibits their growth [18]. Based on these prior findings, as HOXB13 physically interacts with MEIS1 [18], tumors expressing less MEIS1 would be expected to display 21 greater HOXB13 expression and AR activity.…”

“…HOXB13, a homeodomain transcription factor, has been shown to regulate AR activity while shRNA against HOXB13 in LAPC4 cells inhibits their growth [18]. Based on these prior findings, as HOXB13 physically interacts with MEIS1 [18], tumors expressing less MEIS1 would be expected to display 21 greater HOXB13 expression and AR activity. Indeed, we show an inverse relationship between MEIS1 expression and AR activity in two independent cohorts, which is consistent with previous observations of a positive correlation between MYC expression and AR activity [7].…”

MEIS1 down-regulation by MYC mediates prostate cancer development through elevated HOXB13 expression and AR activity

“…We sought to examine the genetic contribution of MYC to the development and progression of primary PCa in the context of dysregulated growth by using anti-MYC immunohistochemistry (IHC) and performing laser capture microdissection on populations of human prostate tumor cells with varying expression of MYC protein. We show using transcriptome profiling that increased MYC activity is inversely correlated with expression of Myeloid Ecotropic viral Insertion Site 1 ( MEIS1 ), a transcription factor that interacts with and regulates the activity of HOX homeodomain transcription factors, including HOXB13 [ 18 – 20 ]. We determined that MYC binding to the MEIS1 locus decreases as MYC levels increase, and that MEIS1 expression is negatively correlated with HOXB13 expression and AR activity.…”