Influence of hypoxia on the proliferation and vincristine drug resistance in neuroblastoma cancer cell lines SHEP-2 and SH-SY5Y

oncology. The primary site of metastasis of neuroblastoma is the bone marrow. A great obstacle in clinical oncology is chemotherapy resistance and relapse in pediatric patients, resulting in a poor prognosis. It is suggested the bone marrow microenvironment plays a crucial role in this process. This microenvironment in which metastatic neuroblastoma cells reside, is hypoxic. Hypoxia is known to affect the malignant behavior and phenotype of tumor cells. Moreover, hypoxia has been reported to activate bone marrow cells to mediate neuroblastoma drug resistance. However, the significance of hypoxia in pediatric cancer and the exact role of chronic hypoxia on the neuroblastoma cell characteristics has yet to be elucidated. Therefore, we aimed to investigate the effects of chronic hypoxia on the cellular response of the SHEP-2 and SH-SY5Y neuroblastoma cell lines, in terms of proliferation and drug resistance. Since the primary site of metastasis of neuroblastoma is the bone marrow, the research further investigates the role of HS-5 primary bone marrow cells on the neuroblastoma cell response in hypoxia. It was observed that proliferation of both SHEP-2 and SH-SY5Y cells was significantly increased in hypoxia, with a near 2-fold increase in proliferation. In co-culture with HS-5, the proliferation was significantly decreased in normoxia, while the proliferation was further increased in hypoxia, compared to the monoculture proliferation. The IC50 of vincristine, a chemotherapy drug commonly used in induction chemotherapy, in normoxia was found to be 0.031±0.008 µM and 0.0019±0.0004 µM for SH-SY5Y and SHEP-2 cells, respectively. In hypoxia the tolerance of the cells for vincristine was significantly increased by 3-fold for both cell lines. The co-culture with HS-5 bone marrow cells did not show a significant difference of the percentage viability compared to the monoculture. These results indicate that hypoxia significantly affects the proliferation of the SHEP-2 and SH-SY5Y neuroblastoma cell lines and the tolerance of both neuroblastoma cell lines to vincristine. Therefore, hypoxia is a microenvironment characteristic that should not be neglected in in vitro drug resistance and tumor behavior studies as it may strongly influence the results and translatability to the patient.