Plocamium cartilagineum extract induces transcriptional changes associated with cell-cycle disruption in C2 canine mastocytoma cells

Introduction: Within an integrative medicine approach that links veterinary and human health, red algae extracts are gaining attention as promising sources of natural bioactive compounds with potential anticancer properties. This study investigates the selectivity of Plocamium cartilagineum extract (PCE) against canine cancer cell lines and its transcriptional effects in C2 canine mastocytoma cells. Methods: Initial cytotoxicity was assessed in C2 canine mastocytoma cells using three assays: Alamar Blue (AB), Neutral Red Uptake (NRU), and Sulforhodamine B (SRB). Selectivity was then investigated using the AB assay in two canine cancer cell lines, C2 and CLBL-1, and two non-cancer canine cell lines, Cf2Th and MDCK. Following the selectivity assessment, the transcriptional responses induced by PCE in C2 cells were investigated by RNA sequencing (RNA-seq) and validated by quantitative PCR (qPCR). Results: PCE exhibited cytotoxic activity in C2 cells, with IC50 values ranging from 42.15 to 77.75 ug/mL across the three assays. In the selectivity assessment, IC50 values ranged from 10.69 ug/mL in CLBL-1 cancer cells to 41.46 ug/mL in Cf2Th non-cancer cells. PCE showed preferential cytotoxicity toward cancer cells, with a selectivity index (SI) reaching 3.9 when comparing CLBL-1 cancer cells with Cf2Th non-cancer cells. RNA-seq and qPCR analyses revealed that PCE induced broad transcriptional changes in C2 cells, including the upregulation of CDKN1A and the downregulation of genes involved in cell-cycle regulation, such as CCNB2, CDC25, and PLK1. Functional enrichment analyses further identified biological processes associated with cell-cycle regulation, DNA repair-related pathways, cellular stress responses, and metabolism. Conclusion: PCE exhibited selective cytotoxic activity toward canine cancer cell lines and induced broad transcriptional alterations in C2 mastocytoma cells. These findings support further investigation of red algae as potential anticancer candidates.