We present an initial molecular characterization of a morphological transition between two early aging states. In previous work, an age score reflecting physiological age was developed using a machine classifier trained on images of worm populations at fixed chronological ages throughout their lifespan. The distribution of age scores identified three stable post-developmental states and transitions. The first transition occurs at day 5 post-hatching, where a significant percentage of the population exists in both state I and state II. The temperature dependence of the timing of this transition (Q 10~1 .17) is too low to be explained by a stepwise process with an enzymatic or chemical rate-limiting step, potentially implicating a more complex mechanism. Individual animals at day 5 were sorted into state I and state II groups using the machine classifier and analyzed by microarray expression profiling. Despite being isogenic, grown for the same amount of time, and indistinguishable by eye, these two morphological states were confirmed to be molecularly distinct by hierarchical clustering and principal component analysis of the microarray results. These molecular differences suggest that pharynx morphology reflects the aging state of the whole organism. Our expression profiling yielded a gene set that showed significant overlap with those from three previous age-related studies and identified several genes not previously implicated in aging. A highly represented group of genes unique to this study is involved in targeted ubiquitin-mediated proteolysis, including Skp1-related (SKR), F-box-containing, and BTB motif adaptors.

Acquired resistance to cisplatin is a major barrier to success in treatment of various cancers, and understanding mitotic mechanisms unique to cisplatin-resistant cancer cells can provide the basis for developing novel mitotic targeted therapies aimed at eradicating these cells. Using cisplatin-resistant models derived from primary patient epithelial ovarian cancer (EOC) cells, we have explored the status of mitotic exit mechanisms in cisplatin-resistant cells. We have uncovered an unexpected role of long-term cisplatin treatment in inducing mitotic exit vulnerability characterized by increased spindle checkpoint activity and functional dependency on Polo-like kinase 1 (PLK1) for mitotic exit in the presence of anaphase promoting complex/cyclosome (APC/C) dysfunction in a cisplatin-resistant state. Accordingly, PLK1 inhibition decreased the survival of cisplatin-resistant cells and and exacerbated spindle checkpoint response in these cells. APC/C inhibition increased sensitivity to pharmacologic PLK1 inhibition, further confirming the existence of APC/C dysfunction in cisplatin-resistant cells. In addition, we uncovered that resistance to volasertib, PLK1 inhibitor, is due to maintenance of cells with low PLK1 expression. Accordingly, stable PLK1 downregulation in cisplatin-resistant cells induced tolerance to volasertib. We provide the first evidence of APC/C dysfunction in cisplatin-resistant state, suggesting that understanding APC/C functions in cisplatin-resistant state could provide a basis for developing novel mitotic exit-based therapies to eradicate cisplatin-resistant cancer cells. Our results also show that PLK1 downregulation could underlie emergence of resistance to PLK1-targeted therapies in cancers. .

<div>Abstract<p><b>Purpose:</b> Acquired resistance to cisplatin is a major barrier to success in treatment of various cancers, and understanding mitotic mechanisms unique to cisplatin-resistant cancer cells can provide the basis for developing novel mitotic targeted therapies aimed at eradicating these cells.</p><p><b>Experimental Design:</b> Using cisplatin-resistant models derived from primary patient epithelial ovarian cancer (EOC) cells, we have explored the status of mitotic exit mechanisms in cisplatin-resistant cells.</p><p><b>Results:</b> We have uncovered an unexpected role of long-term cisplatin treatment in inducing mitotic exit vulnerability characterized by increased spindle checkpoint activity and functional dependency on Polo-like kinase 1 (PLK1) for mitotic exit in the presence of anaphase promoting complex/cyclosome (APC/C) dysfunction in a cisplatin-resistant state. Accordingly, PLK1 inhibition decreased the survival of cisplatin-resistant cells <i>in vitro</i> and <i>in vivo</i> and exacerbated spindle checkpoint response in these cells. APC/C^CDC20 inhibition increased sensitivity to pharmacologic PLK1 inhibition, further confirming the existence of APC/C dysfunction in cisplatin-resistant cells. In addition, we uncovered that resistance to volasertib, PLK1 inhibitor, is due to maintenance of cells with low PLK1 expression. Accordingly, stable PLK1 downregulation in cisplatin-resistant cells induced tolerance to volasertib.</p><p><b>Conclusions:</b> We provide the first evidence of APC/C dysfunction in cisplatin-resistant state, suggesting that understanding APC/C functions in cisplatin-resistant state could provide a basis for developing novel mitotic exit–based therapies to eradicate cisplatin-resistant cancer cells. Our results also show that PLK1 downregulation could underlie emergence of resistance to PLK1-targeted therapies in cancers. <i>Clin Cancer Res; 24(18); 4588–601. ©2018 AACR</i>.</p></div>

<div>Abstract<p><b>Purpose:</b> Acquired resistance to cisplatin is a major barrier to success in treatment of various cancers, and understanding mitotic mechanisms unique to cisplatin-resistant cancer cells can provide the basis for developing novel mitotic targeted therapies aimed at eradicating these cells.</p><p><b>Experimental Design:</b> Using cisplatin-resistant models derived from primary patient epithelial ovarian cancer (EOC) cells, we have explored the status of mitotic exit mechanisms in cisplatin-resistant cells.</p><p><b>Results:</b> We have uncovered an unexpected role of long-term cisplatin treatment in inducing mitotic exit vulnerability characterized by increased spindle checkpoint activity and functional dependency on Polo-like kinase 1 (PLK1) for mitotic exit in the presence of anaphase promoting complex/cyclosome (APC/C) dysfunction in a cisplatin-resistant state. Accordingly, PLK1 inhibition decreased the survival of cisplatin-resistant cells <i>in vitro</i> and <i>in vivo</i> and exacerbated spindle checkpoint response in these cells. APC/C^CDC20 inhibition increased sensitivity to pharmacologic PLK1 inhibition, further confirming the existence of APC/C dysfunction in cisplatin-resistant cells. In addition, we uncovered that resistance to volasertib, PLK1 inhibitor, is due to maintenance of cells with low PLK1 expression. Accordingly, stable PLK1 downregulation in cisplatin-resistant cells induced tolerance to volasertib.</p><p><b>Conclusions:</b> We provide the first evidence of APC/C dysfunction in cisplatin-resistant state, suggesting that understanding APC/C functions in cisplatin-resistant state could provide a basis for developing novel mitotic exit–based therapies to eradicate cisplatin-resistant cancer cells. Our results also show that PLK1 downregulation could underlie emergence of resistance to PLK1-targeted therapies in cancers. <i>Clin Cancer Res; 24(18); 4588–601. ©2018 AACR</i>.</p></div>