The combination of SPP1 knockdown and gemcitabine treatment enhances apoptosis and reduces invasiveness of pancreatic cancer cells

Background Pancreatic ductal adenocarcinoma (PDAC) is poised to be a leading cause of cancer-related deaths. Despite developing new treatment strategies, patient outcomes have not significantly improved. Chemoresistance has been implicated as a major contributor to ineffective treatments observed with studies suggesting combination therapy targeting multiple pathways. This study explored dysregulated genes in tumours of PDAC patients to identify targets which could be used effectively in combination with conventional therapy against cancer cells. Methods In this study, PCR arrays were used for gene expression profiling of tumours obtained from South African PDAC patients to identify key differentially expressed pathways and potentially new therapeutic target genes. SPP1 was selected and RNA interference was used to knock the gene down. Migration and apoptosis assays were used to evaluate the effect of the knockdown, alone and in combination with gemcitabine, on a pancreatic cancer cell line, MIA PaCa-2. Proteomic analysis using SWATH-MS was used to demonstrate potential molecular mechanisms linked to the morphological and phenotypical effects observed with treatment. Results We demonstrated several genes linked to the growth factor and signal transduction signalling pathways, and identified SPP1 as a target. We observed that by combining SPP1 knockdown with conventional chemotherapy, gemcitabine, resulted in a synergistic effect, leading to an enhanced early apoptotic response. A decline of migratory and invasive capabilities of MIA PaCa-2 cells was observed upon subjecting the cancer cells to SPP1 reduction and gemcitabine treatment. Furthermore, proteomic analyses uncovered several pathways that were dysregulated by the combination therapy including both pro-and anti-tumorigenic ones. Conclusion The study findings indicate that SPP1 could be a potential therapeutic target for PDAC, and the possible synergistic effects observed when SPP1 knockdown was combined with gemcitabine treatment suggest a potential avenue for developing more effective treatments for PDAC while exploring tumour cell adaptation for survival. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The study was funded by the National Research Foundation grant (Grant number: 138367) and the Cancer Association of South Africa (CANSA). Proteomics infrastructure used was supported by DIPLOMICS, a research infrastructure initiative of the Department of Science and Innovation of South Africa. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics approval was obtained from the Human Research Ethics Committee (HREC) of the University of the Witwatersrand (Ethics number: M190735) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors