Transcriptomic Profiling of Calcitriol-Mediated Gene Expression Changes in CaSki Human Cervical Cancer Cell Line

The vitamin D endocrine system, primarily mediated by its principal metabolite calcitriol and the vitamin D receptor (VDR), plays a critical role in numerous physiological processes in humans, ranging from calcium metabolism to the prevention of various tumors, including cervical cancer. To comprehensively understand the genomic regulatory effects of calcitriol in a cervical cancer model, this study investigated the transcriptional changes induced by calcitriol in CaSki cells, a cervical cell line harboring multiple copies of HPV16, the primary causal agent of cervical cancer. Initially, we characterized the presence and functionality of the VDR and its co-receptor retinoid X receptor in CaSki cells via immunofluorescence. Subsequently, we assessed the global transcriptome response to calcitriol treatment compared to its vehicle control using microarray analysis, with validation conducted through qPCR and western blot analysis. Our findings revealed that calcitriol regulated over 1000 protein-coding genes, along with some long non-coding RNAs and microRNAs. Overall, calcitriol exerted a repressive effect on the CaSki cell transcriptome, suppressing twice as many genes as it induced. Functional analysis of the results demonstrated that calcitriol suppressed crucial cellular processes involved in cell progression, particularly inhibiting cell proliferation, a finding validated in this study. These results suggest that in this advanced cervical cancer model, calcitriol exhibits a significant antitumor effect by blocking critical processes for tumor progression, underscoring the importance of maintaining adequate vitamin D nutritional status for cervical cancer prevention. For this study, three independent experiments were conducted, each comprising three experimental replicates per experimental condition. From each experimental condition, 3 pools of total RNA were prepared, with each pool comprising an equimolar combination CaSki cells were seeded (150,000 cells) onto 4-well cell culture slides in growth medium. After 24 hours, the medium was aspirated and replaced with either 0.1% ethanol as vehicle or 1x10 -8 M calcitriol in treatment medium.