Hypoxia-mediated centrosome instability as a driver of prostate cancer progression - PROJECT SUMMARY/ABSTRACT There is a fundamental gap in our knowledge to explain the origin of prostate cancer (PCa). Unlike manycancers, point mutations in PCa are relatively infrequent, but, instead, displays large-scale chromosomal instability (CIN). Additionally, hypoxia is a hallmark of prostate tumors, strongly correlates with CIN, and their co-presence synergistically predicts rapid relapse after primary treatment. Mitotic errors are well-established generators of CIN. Normally, two centrosomes guide mitotic spindle shape to ensure bipolarity and accurate chromosome segregation. While centrosome amplification is commonly observed in cancers, we previously reported that centrosomes are absent in localized PCa cells – the first example of centrosome loss in any tumor type. Lime amplification, centrosome loss promotes CIN. Additionally, centrosome elimination causes non-tumorigenic prostate epithelial cells to form proliferative malignant tumors. In contrast to primary tumors, metastasis-derived PCa cells display centrosome amplification, suggesting that centrosome numbers fluctuate during PCa progressions. Our preliminary results suggest that O2 availability is a key determinant of centrosome instability: hypoxia induces centrosome loss, whereas reoxygenation promotes centrosome amplification. Our long-term goal is to discover the underlying mechanisms of CIN that drive PCa progression from indolent localized PCa to lethal metastatic disease, which will deliver new strategies to improve PCa prognosis and treatment. The objective of this application is to determine if O2-dependent centrosome instability contributes to key steps in primary PCa progression and, reciprocally, how changes in O2 microenvironment impact centrosomes. Our central hypothesis is that hypoxia and reoxygenation promote centrosome instability, resulting in both CIN and the formation of HG-PIN lesions. Specifically, hypoxia induces centrosome loss in prostate glands which, in turn, causes CIN, alters cell fate, and promotes migration. Over time, reoxygenation of tumor cells triggers centrosome amplification, enhancing CIN and tumor invasiveness. We will test the following specific aims: 1) Determine the mechanism of hypoxia-mediated centrosome loss in confluent prostate cells. 2) Determine whether cyclic hypoxia induces centrosome instability. 3) Determine whether centrosome loss promotes PIN-like features within organoid models of PCa. Our proposal is innovative because it examines a pathway of PCa progression that is driven, not by mutation, but rather, a prostate’s dynamic microenvironment. Specifically, changes in O2 tension and centrosome instability are mechanistically coupled as drivers of prostate tumor formation and progression. This work is significant because: 1) it will provide a mechanistic link between hypoxia and CIN, which are both hallmarks and agents of PCa evolution, and 2) it will aid therapeutic decisions by identifying non-indolent PCa and minimize overtreatment. Since tumor growth is a complex multimodal event involving host and tumor cells, we use animal xenografts in this proposal as a physiological tumor model that recapitulate human tumor progression (that cannot be accurately evaluated in vitro) because they maintain many of the growth factor, cytokine, and cellular interactions occurring in humans. Mouse is the mammalian model of choice for human disease due to their small size, short generation time, low cost, and ease of handling and caging.
