Cholecalciferol induces apoptosis via autocrine metabolism in epidermoid cervical cancer cells

Mitochondrial protein isoleucyl-tRNA synthetase 2 in tumor cells as a potential therapeutic target for cervical cancer

Objective

Isoleucyl-tRNA synthetase 2 (IARS2) is crucial for mitochondrial activity and function in cancer cells. Cervical cancer is a highly prevalent malignancy affecting the female reproductive system on a global scale. This research investigates the expression and potential roles of IARS2 in cervical cancer cells.

Material and Methods

Initially, we examined the IARS2 expression profile in cervical cancer cells using Western blot technique and quantitative reverse transcription polymerase chain reaction methodologies. Subsequently, cervical cancer cell models with IARS2 silencing and overexpression were constructed using Short Hairpin RNA (ShRNA) (IARS2) and pcMV-FLAG-IARS2, respectively. The impact of IARS2 silencing or overexpression on Hela cell mitochondrial membrane potential, mitochondrial complex I, adenosine triphosphate (ATP) levels, reactive oxygen species activity, viability, proliferation, migration, apoptosis-related proteins, and apoptosis levels was examined through fluorescence staining, enzyme-linked immunosorbent assay, cell counting kit-8 assay, Transwell experiments, Western blot technique, and Terminal deoxynucleotidyl transferase dUTP nick end labeling assay techniques.

Results

The expression of IARS2 is upregulated in cervical cancer cells. Silencing IARS2 with ShRNA (IARS2) disrupts mitochondrial function in cervical cancer cells, resulting in mitochondrial depolarization, heightened oxidative stress, suppression of mitochondrial complex I, and a decrease in ATP levels. Moreover, the depletion of IARS2 significantly impedes the viability, proliferation, and migration of cervical cancer cells, inducing apoptotic processes. In contrast, the overexpression of IARS2 augments the proliferation, migration, and ATP levels in cervical cancer cells.

Conclusion

IARS2 plays a pivotal role as a mitochondrial protein in fostering the growth of cervical cancer cells, presenting itself as an innovative target for tumor diagnosis and treatment.

Dissection of an impact of VDR and RXRA on the genomic activity of 1,25(OH)2D3 in A431 squamous cell carcinoma

BACKGROUND

Human skin is the natural source, place of metabolism, and target for vitamin D3. The classical active form of vitamin D3, 1,25(OH)2D3, expresses pluripotent properties and is intensively studied in cancer prevention and therapy. To define the specific role of vitamin D3 receptor (VDR) and its co-receptor retinoid X receptor alpha (RXRA) in genomic regulation, VDR or RXRA genes were silenced in the squamous cell carcinoma cell line A431 and treated with 1,25(OH)2D3 at long incubation time points 24 h/72 h. Extending the incubation time of A431 WT (wild-type) cells with 1,25(OH)2D3 resulted in a two-fold increase in DEGs (differentially expressed genes) and a change in the amount of downregulated from 37% to 53%. VDR knockout led to a complete loss of 1,25(OH)2D3-induced genome-wide gene regulation at 24 h time point, but after 72 h, 20 DEGs were found, of which 75% were downregulated, and most of them belonged to the gene ontology group "immune response". This may indicate the existence of an alternative, secondary response to 1,25(OH)2D3. In contrast, treatment of A431 ΔRXRA cells with 1,25(OH)2D3 for 24 h only partially affected DEGs, suggesting RXRA-independent regulation. Interestingly, overexpression of classic 1,25(OH)2D3 targets, like CYP24A1 (family 24 of subfamily A of cytochrome P450 member 1) or CAMP (cathelicidin antimicrobial peptide) was found to be RXRA-independent. Also, immunofluorescence staining of A431 WT cells revealed partial VDR/RXRA colocalization after 24 h and 72 h 1,25(OH)2D3 treatment. Comparison of transcriptome changes induced by 1,25(OH)2D3 in normal keratinocytes vs. cancer cells showed high cell type specific expression pattern with only a few genes commonly regulated by 1,25(OH)2D3. Activation of the genomic pathway at least partially reversed the expression of cancer-related genes, forming a basis for anti-cancer activates of 1,25(OH)2D3. In summary, VDR or RXRA independent genomic activities of 1,25(OH)2D3 suggest the involvement of alternative factors, opening new challenges in this field.

The Preventive Role of the Vitamin D Endocrine System in Cervical Cancer

Vitamin D along with its active metabolite calcitriol and its metabolic and signaling system, known as the vitamin D endocrine system, have been widely recognized as a pivotal regulator of calcium homeostasis in addition to non-calcemic antitumoral effects in a variety of human cancers, including cervical cancer. Several studies have found an inverse relationship between the incidence of cervical neoplasia and vitamin D levels. This narrative review updates the current evidence supporting the notion that the vitamin D endocrine system has a preventive role on cervical cancer, mainly in the early phases of the disease, acting at the level of suppressing cell proliferation, promoting apoptosis, modulating inflammatory responses, and probably favoring the clearance of human papillomavirus-dependent cervical lesions. Although an optimal vitamin D status helps in the prevention and regression of low-grade squamous intraepithelial lesions of the cervix, it appears that vitamin D alone or combined with chemotherapeutic agents has little effectivity once advanced cervical cancer is established. These observations suggest that an optimal vitamin D status might exert beneficial actions in the early phases of cervical cancer by preventing its onset and progression.

25-Hydroxycholecalciferol Inhibits Cell Growth and Induces Apoptosis in SiHa Cervical Cells via Autocrine Vitamin D Metabolism

Preclinical studies show that the anticancer actions of vitamin D metabolites are mediated by apoptosis, inhibition of cell proliferation and induction of cell cycle arrest. Cervical cancer cells express an autocrine vitamin D metabolising system (VDMS) comprised of a vitamin D receptor, vitamin D catabolic enzyme (CYP24A1), and the activating enzyme of 25-hydroxycholecalciferol (25(OH)D3), CYP27B1. We assessed the anticancer effects of 25(OH)D3 at clinically relevant concentrations on a cervical squamous cell cancer cell line, SiHa. We evaluated cell health parameters (cell count, viability, and cell cycle), cell death modes (apoptosis, autophagic-dependent death, and necrosis by flow cytometry and transmission electron microscopy), and autocrine VDMS gene and protein expression by qPCR and Western blot, respectively. Our study demonstrates that physiological and supraphysiological doses of 25(OH)D3 inhibit cell growth and viability and induce biochemical and morphological apoptosis in SiHa cells. These growth effects are mediated by alteration in the VDMS gene and protein expression, with prominent negative feedback at supraphysiological treatment dose. These data identify promising therapeutic potential of 25(OH)D3 in cervical cancer, which warrants further clinical translational investigations.