MOLECULAR DISECTION OF BIOLOGICALLY RELEVANT PATHWAYS AFTER INHIBITION OF CHECKPOINT KINASE 1

NICOLÁS CALZETTA; MARINA GONZÁLEZ; NATALIA PAVIOLO; VANESA GOTTIFREDI

Buenos Aires

Congreso; Reunión Conjunta de Biociencias; 2017

Sociedades Argentinas de Biociencias

Checkpoint signalling allows tumour cells to cope with high ratesof replication stress, a hallmark of cancer. Specifically, Chk1 delaysthe progression of S phase, thereby increasing the chances to repairdamaged DNA before using it as a replication template. Therefore,the inhibition of checkpoint kinase 1 (Chk1) has emerged as a promising anti-cancer therapy. However, in the clinic, treatments withChk1 inhibitors fail with unexpected frequency, highlighting the needto further understand how cells adapt to such therapy. It is very wellestablished that Chk1 inhibition alters the replication choreography,increasing origin firing while slowing down replication fork progression. In turn, such defective replication choreography generatesincreased levels of double strand break (DSB), compromising thegenomic stability of cells to a degree that triggers cell death. Thecurrent model proposes that such events are part of a linear pathway, so that cell death is intimately linked to genomic instability inChk1-inhibited cells. However, the molecular signals that link thosephenotypes are unknown. We have undertaken a systematic analysis involving the elimination of factors which are crucial for each ofthe processes modulated by Chk1 inhibition. In such experimentalsettings, we have examined the replication choreography (DNA fiberassay which allows to measure fork rate and percentage of originfiring). We have also quantified DSB accumulation using neutralCOMET assay and genomic instability using the micronuclei assay.We will present preliminary data demonstrating that the phenotypescaused by Chk1 deficiency, i.e. altered replication choreography, genomic instability, and cell death can be dissected at the molecularlevels. We believe that such information could be used to improveanti-cancer therapies based on Chk1 inhibition