Characterization of the sperm factor Phospholipase C zeta (PLCζ), in mammalian cancer.

During mammalian fertilization, oocyte activation initiates embryogenesis in response to specific intracellular calcium(Ca2+) patterns, driven by a sperm / testis-specific protein, Phospholipase C zeta(PLCζ). PLCζ triggers Ca2 + release from the endoplasmic reticulum(ER) via the inositol triphosphate(IP3) pathway. PLCζ abrogation is linked to male-factor infertility and abnormal embryogenesis in humans, while PLCζ mutations from infertile patients resulted in loss of activity, abnormal Ca2+ + release, and unsuccessful oocyte activation. Although PLCζ has been extensively suggested to be testis - and sperm - specific, some studies have suggested expression in brain and ovarian tissue of mice and fish.Thus, we aimed to further investigate the expression of PLCζ in non - testicular tissue in mouse and human tissue.Since phospholipase C is implicated in dysregulating Ca2+ signalling in various cancers, we extended our examinations to human cancer tissue and cancer cell lines.

Using multiple validated PLCζ-specific antibodies, we wanted to study the presence of PLCζ in non-testicular tissues in both mice and humans. Immunoblotting was done to compare PLCζ levels in tumor tissues and matched normal controls from ovarian, brain, prostate, and testicular cancer tissues and cell lines. Additionally, we examined the NIH National Cancer Institute\'s Genetic Data Commons (GDC) to identify various PLCζ mutations across various cancer tissues. A preliminary bioinformatics analysis was done to predict the potential impact of these mutations on PLCζ activity.

Immunoblotting indicated that PLCζ levels in tumor tissues were ~50 - fold higher than matched normal controls across ovarian, brain, prostate, and testicular cancers and cell lines. Analysis of the GDC revealed multiple mutations within the PLCζ gene across different cancer types, with eight mutations identified in more than three patients. Preliminary bioinformatics analysis suggests that most of these mutations likely have damaging effect on PLCζ activity.

Collectively, our analyses represent exciting avenues for examining PLCζ in non-testicular tissue but also indicate the potential presence of PLCζ and differential isoforms of PLCζ with potentially novel further roles. Furthermore, our results indicate a novel paradigm for the examination of PLCζ in non-testicular human tissue, but could also represent a significant advance in our understanding of Ca2+ signalling in cancer.