Algal extracts as potential anticancer agents: preliminary investigations in C2 canine mastocytoma cell line

Introduction: Cancer chemotherapy is one of the most commonly adopted therapeutic approach in pets oncology. However, the adverse side effects caused by chemotherapeutic drugs and the drug resistance developed by the tumours over time, are of primary concern. Thus, alternative natural sources, more specific and less toxic than anticancer agents, are actually considered. In this respect, bioactive compounds with proven cytotoxic, antiproliferative, antioxidant, anti-inflammatory and immunomodulatory effects have been recently isolated from different marine sources, especially from seaweeds (1). The aim of the present study was to investigate the antiproliferative and cytotoxic potential of three red marine macroalgae, Plocamium cartilagineum (PC), Gracilaria cervicornis (GC) and Halopitys incurvus (HI), and one brown macroalga, Laminaria ochroleuca (LO), collected from the Moroccan coast, on C2 canine mast cell tumour cell line. Materials and Methods: Crude algal extracts were prepared from dried algal powder by organic extraction (dichloromethane:methanol, 1:1 v/v) and were preliminarily assayed for their cytotoxic potential at 48 hrs using Alamar Blue (AB) dye. The two extracts showing the lowest IC50 were then selected for the determination of the cytotoxic activity using three different assays (i.e., Alamar Blue, Sulforhodamine B, SRB, and Neutral Red Uptake, NRU), and for RNA-seq analyses. As to transcriptomic investigations, two sub-cytotoxic concentrations (IC15 and IC30) for each alga were selected. Results: At the preliminary screening, GC and PC showed a ~15-fold lower IC50 compared to HI and LO (IC50 29.7 and 26.57 µg/mL vs 487.8 and 361.6 µg/mL, respectively). Therefore, GC and PC algae were selected for the subsequent analyses. The cytotoxicity data (IC50) were quite consistent among the three assays used either for GC (26.41, 20.05 and 34.55 µg/mL using AB, SRB and NRU, respectively) than for PC (50.74, 42.15 and 77.75 µg/mL using AB, SRB and NRU, respectively) and showed the highest sensitivity of C2 cells towards GC. Conclusion: Overall, GC displayed the greatest effectiveness against C2 cell line compared to other three algal extracts, as previously reported in different human cancer cell lines (2). Ongoing transcriptomic analyses will consent to confirm these results and help to elucidate GC and PC molecular mechanism of action. Moreover, the analytical characterization (GC-MS) of the main bioactive compounds responsible of the anti-proliferative activity is envisaged.