Abstract
Non-small cell lung cancer (NSCLC) is one of the most common diagnoses globally and is often aggressive in its morphology and development of resistance to chemotherapeutic treatment. A prominent driver of both malignancy and drug resistance is chromosomal instability (CIN). CIN allows cells to change their DNA content with each cell division and bypass DNA repair processes - allowing for the evolution of atypical phenotypes, resistance, and ultimately poor patient prognosis. Similarly to CIN, the Y-Box binding-1 (YB-1) cold shock protein is highly involved in chromosomal segregation and division during mitosis and cytokinesis - resulting in mis-segregation and abnormal genetic profiles. Furthermore, it is well established that increased levels of YB-1 can promote resistance to paclitaxel (PTX), a mitotic stabiliser frequently used to treat NSCLC patients. It is unknown whether sustained expression of YB-1 mediates CIN to promote resistance to PTX treatment.
This project sought to investigate the relationship between increased YB-1 expression, CIN, and PTX resistance using H1299 NSCLC cells stably expressing tetracycline inducible (Tet-One) YB-1. Cells were either induced to increase YB-1 or left at endogenous expression, then treated with a dose range of PTX for 24-hours. Induction of YB-1 was confirmed using western blot. To determine the influence of increased YB-1 levels on CIN post PTX treatment, confocal live cell imaging was conducted for 60 hours. This data was used to assess abnormalities in the cell cycle and to visualise cellular morphologies indicative of CIN - micronuclei, multinucleation, abnormal nuclear structures, and events of mitotic catastrophe. It was seen that YB-1 induced cells had a lower amount of CIN at low doses of PTX compared to uninduced cells, suggesting that YB-1 was allowing cells to maintain abnormal phenotypes at survivable levels at lower drug concentrations. This was substantiated with long-term colony formation assays, where there was a greater number of surviving colonies at low doses of PTX in YB-1 induced cells.
These experiments demonstrated that increased YB-1 expression may have a protective effect in low doses of PTX, which may subsequently lead to sustainable growth and the development of treatment resistance in NSCLC cells. It can be suggested there is a correlation between elevated YB-1 and CIN, and this is a mechanism by which cancerous cells are able to proliferate despite PTX chemotherapy.