Role of DNA methylation in INK4a-ARF-INK4b locus expression in breast cancer

Breast cancer is a public health problem : one woman in 9 will suffer of it during her lifetime. The estrogen receptor expressing sub-type (ER+) is the most frequent, with 75 % of the cases. Those tumors frequently become resistant to hormonotherapy and spread as metastasis. In this case, chemotherapy needs to be administrated. The CDK4/6 inhibitors in combination with hormonotherapy appears as the new standard treatment for metastatic disease and allows to postpone the chemotherapy. Those drugs play the same role as the endogenous p16-p15 proteins, and it is expected that the patients who have lost their protein expression are also those who will present the best response to treatment. However, none of the currently tested biomarkers turns out to be predictive of treatment response. The INK locus, where p16/p14-p15 proteins are encoded, is often altered in cancers and is involved in cell cycle regulation. The p16/p14-p15 expression is negatively regulated by a non-coding RNA called ANRIL. My aim is to explore the molecular mechanisms linked to the non-coding RNA of the INK locus and involved in the expression regulation of the proteins p16/p14-p15, and to highlight potential biomarkers of the CDK4/6 inhibitors treatment response in ER+ breast cancer.
To this end, I already collected In Vitro expression data by RT-qPCR in some cell lines with different expression patterns. DNA methylation are investigated thanks to a Deoxyazacytidine treatment, a DNA methylation inhibitor then by ImmunoPrecipitation of methylated DNA. So, the first links between the expression of the locus and its methylation can be done. In future, other treamtents, protein and RNA interactions will be studied to explain the potential links and molecular mechanisms.