Exploring Less Toxic Combination Treatment Options for Inducing Anti-Cancer Activity in Medulloblastoma Cells

Purpose.Medulloblastoma (MB) is the most common type of malignant pediatric brain cancer and is typically located in the posterior fossa. There are four subgroups within MB: Wnt, Sonic-Hedgehog, Group 3, and Group 4. Due to differences in pathology, signaling pathways, and gene expression, each subgroup is approached differently with respect to treatment, based upon differences in prognosis. Currently, the standard treatment approaches include surgical resection, radiotherapy, and chemotherapeutic agents such as etoposide, vincristine, and cisplatin. Survivors often suffer from severe long-term side effects including neurocognitive deficits and the potential for a future second neoplasm due to the tumorigenic potential of aggressive combination therapies. Because of these side-effects, there is an urgent need for effective and less toxic therapeutic strategies for the treatment of MB. Through prior research we have demonstrated the combination of etoposide alongside less toxic anti-cancer agents potentially increases anti-cancer activity in Ewing Sarcoma. We hypothesize that using a combination of etoposide with other sensitizing agents can also enhance the anti-cancer activity in MB cell lines. Methods. DAOY cells were cultured with increasing concentrations of Etoposide (ETO), Mithramycin-A (MIT), BNS-22 and Tolfenamic acid (TA) and the cell growth was monitored at 48 hours using CellTiter-Glo kit (luminescence cell viability assay). Dose-curves were then generated using sigma-plot software. After calculating the IC50 values for each agent, low dose of ETO (half of IC50 value) and IC50 value of other agents were tested for the combination treatment. Results. Overall, we observed decreased cell viability in a dose and time dependent manner for all tested agents. The IC50 values derived from the dose curves were 1 µg/ml for ETO, 33.3 nM for MIT, 15 µg/ml for TA, and 14.5 µM for BNS. The combination treatment using 0.5 µg/ml ETO and other agents (IC50 values) showed cell growth inhibition greater than any single agent in DAOY cells. The analysis revealed that the combination of ETO (0.5 µg/ml) plus BNS-22 was very effective. Conclusions: These preliminary data demonstrate promise in creating combination therapy of ETO with BNS-22 to treat DAOY cell lines. For better applications, similar experiments should be done with more cell lines representing various sub-groups of MB and to be confirmed by in vivoassays.