Transfer of healthy fibroblast-derived mitochondria to HeLa ρ and SAS ρ cells recovers the proliferation capabilities of these cancer cells under conventional culture medium, but increase their sensitivity to cisplatin-induced apoptotic death.

Mitochondrial dysfunction is known to contribute to cancer initiation, progression, and chemo-and radio-resistance. However, the precise role of mitochondria in cancer is controversial. Hence, here we tried to further clarify the role of mitochondria in cancer by transferring healthy mitochondria to cancer cells, and also to cells with depleted mitochondrial DNA (ρ). Healthy mitochondria were isolated from WI-38 cells and were transferred to HeLa, SAS, HeLa ρ and SAS ρ cells. Then, cell proliferation was verified. In addition, the cells were treated by different concentrations of cisplatin and assessed for apoptosis induction and quantifying the mRNA expression of apoptosis-related genes. Results revealed that incubation of the HeLa, SAS and HeLa ρ cells with 5 µg/ml of the isolated mitochondria for 24 h significantly (p < 0.001) increased cell proliferation compared to non-treated controls. Interestingly, the mitochondria transfer rescued the ρ cells and made them capable of growing under conventional culture medium. However, the number of apoptotic cells was significantly higher in the HeLa ρ cells that received the mitochondria (HeLa-Fibro-Mit) compared to the HeLa ρ. Furthermore, the expression level of BCL-2 anti-apoptotic gene was down-regulated in both HeLa-Fibro-Mit and SAS-Fibro-Mit cell lines while the expression levels of the BAX, caspase8, caspase9, and AIF pro-apoptotic genes were upregulated. Our findings indicated that although the response of cancer cells to the mitochondria transfer is cancer-type dependent, but the introduction of normal exogenous mitochondria to some cancer cells might be considered as a potential novel therapeutic strategy.