A functional genomics screen reveals a strong synergistic effect between docetaxel and the mitotic gene DLGAP5 that is mediated by the androgen receptor

Abstract

Based on a molecular classification of prostate cancer using gene expression pathway signatures, we derived a set of 48 genes in critical pathways that significantly predicts clinical outcome in all tested patient cohorts. We tested these genes in a functional genomics screen in a panel of three prostate cancer cell lines (LNCaP, PC3, DU145), using RNA interference. The screen revealed several genes whose knockdown caused strong growth inhibition in all cell lines. Additionally, we tested the gene set in the presence of docetaxel to see whether any gene exhibited additive or synergistic effects with the drug. We observed a strong synergistic effect between DLGAP5 knockdown and docetaxel in the androgen-sensitive line LNCaP, but not in the two other androgen-independent lines. We then tested whether this effect was connected to androgen pathways and found that knockdown of the androgen receptor by si-RNA attenuated the synergy significantly. Similarly, androgen desensitized LNCaP-AI cells had a higher IC50 to docetaxel and did not exhibit the synergistic interaction. Short-term exposure to enzalutamide did not significantly alter the behaviour of parental LNCaP cells. An immunofluorescence analysis in LNCaP cells suggests that under the double insult of DLGAP5 knockdown and docetaxel, cells predominantly arrest in metaphase. In contrast, the knockdown of the androgen receptor by siRNA appears to assist cells to progress through metaphase in to anaphase, even in the presence of docetaxel. Our data suggest that DLGAP5 has a unique function in stabilizing spindle formation and surviving microtubule assault from docetaxel, in an androgen-regulated cell cycle system.

Elevated mRNA expression levels of DLGAP5 are associated with poor prognosis in breast cancer

“…The human discs large-associated protein 5 (DLGAP5) gene, which is mapped to chromosome 14q22.3, is a cell cycle regulator involved in carcinogenesis (9). Wang et al (10) reported that DLGAP5 was upregulated in non-small cell lung cancer (NSCLC) and was associated with a shorter survival time.…”

Bioinformatics analysis combined with experiments to explore potential prognostic factors for pancreatic cancer

“…Horning et al found the upregulation of DLGAP5 expression to be associated with recurrent prostate cancer [24]. DLGAP5 can stabilize spindle formation, leading to survival despite a microtubule challenge of docetaxel in androgen-regulated prostate cancer cell cycle systems [25]. DLGAP5 is also a direct downstream target of NOTCH3, which partially explains the mechanism of how NOTCH3 activation promotes ovarian cancer from the perspective of mitotic aberrations [26].…”

Identification of key biomarkers associated with development and prognosis in patients with ovarian carcinoma: evidence from bioinformatic analysis

“…DLGAP5, disc large homolog associated protein 5, has a pivotal role in spindle assembly and chromosomal segregation during mitosis, which has been found to be unregulated in several cancer types, including OC, colorectal cancer (CRC), HCC, and adrenocortical tumors [31–34]. Depletion of DLGAP5 can lead to prolonged prometaphase and aberrant chromatin segregation.…”

“…Overexpression of DLGAP5 induces the accumulation of the oncoprotein Gankyrin leading to the ubiquitination and degradation of P53 [33]. In prostate cancer, studies indicated that loss of DLGAP5 gene sensitizes androgen-dependent LNCaP cells to docetaxel treatment due to lower density of microtubule in their central spindles which requires a lower molecule content of drug to bind and stabilize the microtubule, suggesting that DLGAP5 may provide a potential novel target for chemotherapy efficacy [34]. In OC, considerable evidence shows an important oncogenic role of Notch signaling [35–37].…”