Worldwide, the number of cancer-related deaths continues to increase due to the ability of cancer cells to become chemotherapy-resistant and metastasize. For women with ovarian cancer, a staggering 70% will become resistant to the front-line therapy, cisplatin. Although many mechanisms of cisplatin resistance have been proposed, the key mechanisms of such resistance remain elusive. The RNA binding protein with multiple splicing (RBPMS) binds to nascent RNA transcripts and regulates splicing, transport, localization, and stability. Evidence indicates that RBPMS also binds to protein members of the AP-1 transcription factor complex repressing its activity. Until now, little has been known about the biological function of RBPMS in ovarian cancer. Accordingly, we interrogated available Internet databases and found that ovarian cancer patients with high RBPMS levels live longer compared to patients with low RBPMS levels. Similarly, immunohistochemical (IHC) analysis in a tissue array of ovarian cancer patient samples showed that serous ovarian cancer tissues showed weaker RBPMS staining when compared with normal ovarian tissues. We generated clustered regularly interspaced short palindromic repeats (CRISPR)-mediated RBPMS knockout vectors that were stably transfected in the high-grade serous ovarian cancer cell line, OVCAR3. The knockout of RBPMS in these cells was confirmed via bioinformatics analysis, real-time PCR, and Western blot analysis. We found that the RBPMS knockout clones grew faster and had increased invasiveness than the control CRISPR clones. RBPMS knockout also reduced the sensitivity of the OVCAR3 cells to cisplatin treatment. Moreover, β-galactosidase (β-Gal) measurements showed that RBPMS knockdown induced senescence in ovarian cancer cells. We performed RNAseq in the RBPMS knockout clones and identified several downstream-RBPMS transcripts, including non-coding RNAs (ncRNAs) and protein-coding genes associated with alteration of the tumor microenvironment as well as those with oncogenic or tumor suppressor capabilities. Moreover, proteomic studies confirmed that RBPMS regulates the expression of proteins involved in cell detoxification, RNA processing, and cytoskeleton network and cell integrity. Interrogation of the Kaplan–Meier (KM) plotter database identified multiple downstream-RBPMS effectors that could be used as prognostic and response-to-therapy biomarkers in ovarian cancer. These studies suggest that RBPMS acts as a tumor suppressor gene and that lower levels of RBPMS promote the cisplatin resistance of ovarian cancer cells.

Despite initial responses to first-line treatment with platinum and taxane-based combination chemotherapy, most high-grade serous ovarian carcinoma (HGSOC) patients will relapse and eventually develop a cisplatin-resistant fatal disease. Due to the lethality of this disease, there is an urgent need to develop improved targeted therapies against HGSOC. Herein, we identified CASC10, a long noncoding RNA upregulated in cisplatin-resistant ovarian cancer cells and ovarian cancer patients. We performed RNA sequencing (RNA-seq) in total RNA isolated from the HGSOC cell lines OVCAR3 and OV-90 and their cisplatin-resistant counterparts. Thousands of RNA transcripts were differentially abundant in cisplatin-sensitive vs. cisplatin-resistant HGSOC cells. Further data filtering unveiled CASC10 as one of the top RNA transcripts significantly increased in cisplatin-resistant compared with cisplatin-sensitive cells. Thus, we focused our studies on CASC10, a gene not previously studied in ovarian cancer. SiRNA-mediated CASC10 knockdown significantly reduced cell proliferation and invasion; and sensitized cells to cisplatin treatment. SiRNA-mediated CASC10 knockdown also induced apoptosis, cell cycle arrest, and altered the expression of several CASC10 downstream effectors. Multiple injections of liposomal CASC10-siRNA reduced tumor growth and metastasis in an ovarian cancer mouse model. Our results demonstrated that CASC10 levels mediate the susceptibility of HGSOC cells to cisplatin treatment. Thus, combining siRNA-mediated CASC10 knockdown with cisplatin may represent a plausible therapeutic strategy against HGSOC.

Studies underestimate the microbial diversity and genotypic traits in the snails’ microbiome. Caracolus marginella, a land snail native to Caribbean islands, can adapt to different environments. Our research focused on the generation of a metagenomic library from C. marginella gut, to further explore the diversity and functional traits. Thirty specimens of C. marginella were collected from the four regions of Puerto Rico. High molecular weight (40 kb) metagenomic libraries were generated using a direct DNA isolation method. DNA was end-repaired and ligated into a pCCFOS1 fosmid vector; then, the cloned DNA was transduced into Escherichia coli EPI300. The master pool library contains approximately 60,200 clones and restriction enzyme digestion showed that 90% of the library contains insert. After removing the fosmid and host genome sequences, 567,015 sequences were analyzed using the MG-RAST online server. The Bacteria domain was the most abundant (82.15%), followed by viruses (16.49%), eukaryotes (0.83%) and archaea (0.31%). The Proteobacteria (51.47%) was predominant in the gut environment, followed by unidentified virus (16.28%), and Actinobacteria (8.52%). Escherichia coli, Streptomyces avermitilis, and Burkholderia sp. were the most abundant species present. Subsystem functional analysis showed that 35.00% of genes belong to transposable elements, 10.00% of genes belong to clustering-based subsystems, 4.00% of genes belong to the production of cofactors and secondary metabolites, and 2.00% resistance to antibiotics and toxic compounds. The data generated in this research is the first metagenomic examination of a snail gut in Puerto Rico, and will serve as a baseline to start understanding of C. marginella gut microbiome.