Background: Retinoblastoma is a sight and life-threatening embryonal tumor in children. Though chemotherapy is the main mode of therapy, evolving resistance remains a major obstacle in treatment success. The presence of cancer stem cells (CSC) is frequently reported to be responsible for chemoresistance in multiple tumors.
Objective: Our study aims to identify the molecular factors that facilitate the chemoresistance through cancer stem cells in retinoblastoma.
Methods: We developed etoposide and carboplatin resistant retinoblastoma (Y79) cell lines by stepwise drug increment treatment, validated with MTT and TUNEL assays. Colony forming and invasive ability were studied by soft-agar colony forming and transwell assays, respectively. Similar analysis in non-responsive retinoblastoma tumors were carried out by histopathology. Finally, expression of CSC/neuronal markers and ABC transporters were examined by quantitative PCR and protein expression of neuronal stem cell markers was confirmed by Western blot.
Results: Larger colony size of resistant cells in soft-agar assay provided evidence for increased selfrenewability. Histopathology in non-responsive tumors showed poorly differentiated cells predominantly. Besides, both resistant cell lines and non-responsive tumors showed increased invasion with higher expression of neuronal stem cell markers - SOX2, NANOG, OCT4 and ABC transporters - ABCB1 and ABCC3. Increased self-renewal ability and invasion along with overexpression of stemness markers in resistant cells and tumors provide evidence for stemness driving chemoresistance and invasion in retinoblastoma.
Conclusion: We have demonstrated Neuronal stem cell/CSC markers that facilitate the maintenance of cancer stem cells. Developing therapies targeting these factors will help in overcoming resistance and improving retinoblastoma treatment.
[http://dx.doi.org/10.1038/ncb1589] [PMID: 17515932]
[http://dx.doi.org/10.1111/j.1469-7580.2010.01269.x] [PMID: 20646110]]
[http://dx.doi.org/10.21873/anticanres.13858] [PMID: 31810908]
[http://dx.doi.org/10.1074/jbc.M800109200] [PMID: 18441325]
[http://dx.doi.org/10.1371/journal.pone.0208194] [PMID: 30513115]
[http://dx.doi.org/10.21873/anticanres.12985] [PMID: 30396949]