A ‘synthetic-sickness’ screen for senescence re-engagement targets in mutant cancer backgrounds

Abstract

Senescence is a universal barrier to immortalisation and tumorigenesis. As such, interest in the use of senescence-induction in a therapeutic context has been gaining momentum in the past few years; however, senescence and immortalisation remain underserved areas for drug discovery owing to a lack of robust senescence inducing agents and an incomplete understanding of the signalling events underlying this complex process. In order to address this issue we undertook a large-scale morphological siRNA screen for inducers of senescence phenotypes in the human melanoma cell line A375P. Following rescreen and validation in a second cancer cell line, HCT116 colorectal carcinoma, a panel of 16 of the most robust hits were selected for further validation based on significance and the potential to be targeted by drug-like molecules. Using secondary assays for detection of senescence biomarkers p21, 53BP1 and senescence associated beta-galactosidase (SAβGal) in a panel of HCT116 cell lines carrying cancer-relevant mutations, we show that partial senescence phenotypes can be induced to varying degrees in a context dependent manner, even in the absence of p21 or p53 expression. However, proliferation arrest varied among genetic backgrounds with predominantly toxic effects in p21 null cells, while cells lacking PI3K mutation failed to arrest. Furthermore, we show that the oncogene ECT2 induces partial senescence phenotypes in all mutant backgrounds tested, demonstrating a dependence on activating KRASG13D for growth suppression and a complete senescence response. These results suggest a potential mechanism to target mutant KRAS signalling through ECT2 in cancers that are reliant on activating KRAS mutations and remain refractory to current treatments.

Streptococcus gallolyticus abrogates anti-carcinogenic properties of tannic acid on low-passage colorectal carcinomas

“…TA increases the production of reactive oxygen species by altering the redox balance in the cell. This finally induces cell cycle arrest as described for HCT116 cells 38 , supported by our own observations. TA is thus considered a potential anticancer agent [39][40][41] , with additional ability to act as chemosensitizer 42 .…”

A Novel Pyrazolopyrimidine Ligand of Human PGK1 and Stress Sensor DJ1 Modulates the Shelterin Complex and Telomere Length Regulation

“…In a genome-wide siRNA screen for senescence regulators, we recently identified ALDOA as a strong candidate for inhibition to induce accelerated senescence in cancer cells [18]. Our current results shed new light on the complexity of coupling between immortality/senescence and metabolism.…”

“…We have previously applied cell based- and virtual-screening approaches for target and compound identification to selectively modulate telomere signaling pathways [16], [17], [18], [19]. We now report characterization of CRT0063465, a novel pyrazolopyrimidine compound that emerged from cell-based screens of telomere signaling.…”

Tetraploidy in cancer and its possible link to aging

“…A recent report verified the relationship between tetraploidy and cardiomyocyte regeneration in zebrafish by inhibiting epithelial cell transforming sequence 2 oncogene ( ECT2 ), a major player in cytokinesis regulated by Rho GTPases and in DNA damage responses . Knockdown of ECT2 induced senescence markers in a spontaneously immortalized non‐transformed mammary epithelial cell line with a KRAS mutation . In adult zebrafish, transient inhibition of Ect2 increased tetraploidy in the heart and inhibited regeneration after apical ventricular resection .…”

“…78 Knockdown of ECT2 induced senescence markers in a spontaneously immortalized non-transformed mammary epithelial cell line with a KRAS mutation. 79 In adult zebrafish, transient inhibition of Ect2 increased tetraploidy in the heart and inhibited regeneration after apical ventricular resection. 80 These findings suggest that increased tetraploidy of cardiomyocytes and resultant decreased regeneration is a phenotype related to cellular senescence.…”