Browsing by Author "Zhao, J. J."

Now showing 1 - 2 of 2

Open Access
Blocking PI3K p110β attenuates development of PTEN-deficient castration-resistant prostate cancer
(American Association for Cancer Research, 2022-01-26) Gao, X.; Wang, Y.; Ribeiro, C. F.; Manokaran, C.; Chang, H.; Von, T.; Rodrigues, S.; Çizmecioğlu, Onur; Jia, S.; Korpal, M.; Korn, J. M.; Wang, Z.; Schmit, F.; Jiang, L.; Pagliarini, R.; Yang, Y.; Sethi, I.; Signoretti, S.; Yuan, G.; Loda, M.; Zhao, J. J.; Roberts, T. M.
A common outcome of androgen deprivation in prostate cancer therapy is disease relapse and progression to castration-resistant prostate cancer (CRPC) via multiple mechanisms. To gain insight into the recent clinical findings that highlighted genomic alterations leading to hyperactivation of PI3K, we examined the roles of the commonly expressed p110 catalytic isoforms of PI3K in a murine model of Pten-null invasive CRPC. While blocking p110α had negligible effects in the development of Pten-null invasive CRPC, either genetic or pharmacologic perturbation of p110β dramatically slowed CRPC initiation and progression. Once fully established, CRPC tumors became partially resistant to p110β inhibition, indicating the acquisition of new dependencies. Driven by our genomic analyses highlighting potential roles for the p110β/RAC/PAK1 and β-catenin pathways in CRPC, we found that combining p110β with RAC/PAK1 or tankyrase inhibitors significantly reduced the growth of murine and human CRPC organoids in vitro and in vivo. Because p110β activity is dispensable for most physiologic processes, our studies support novel therapeutic strategies both for preventing disease progression into CRPC and for treating CRPC.
Open Access
Oncogenic kinase-induced PKM2 tyrosine 105 phosphorylation converts nononcogenic PKM2 to a tumor promoter and induces cancer stem-like cells
(American Association for Cancer Research, 2018) Zhou, Z.; Li, M.; Zhang, L.; Zhao, H.; Şahin, Özgür; Chen, J.; Zhao, J. J.; Songyang, Z.; Yu, D.
The role of pyruvate kinase M2 isoform (PKM2) in tumor progression has been controversial. Previous studies showed that PKM2 promoted tumor growth in xenograft models; however, depletion of PKM2 in the Brca1-loss–driven mammary tumor mouse model accelerates tumor formation. Because oncogenic kinases are frequently activated in tumors and PKM2 phosphorylation promotes tumor growth, we hypothesized that phosphorylation of PKM2 by activated kinases in tumor cells confers PKM2 oncogenic function, whereas nonphosphorylated PKM2 is nononcogenic. Indeed, PKM2 was phosphorylated at tyrosine 105 (Y105) and formed oncogenic dimers in MDA-MB-231 breast cancer cells, whereas PKM2 was largely unphosphorylated and formed nontumorigenic tetramers in nontransformed MCF10A cells. PKM2 knockdown did not affect MCF10A cell growth but significantly decreased proliferation of MDA-MB-231 breast cancer cells with tyrosine kinase activation. Multiple kinases that are frequently activated in different cancer types were identified to phosphorylate PKM2-Y105 in our tyrosine kinase screening. Introduction of the PKM2-Y105D phosphomimetic mutant into MCF10A cells induced colony formation and the CD44hi/ CD24neg cancer stem–like cell population by increasing Yesassociated protein (YAP) nuclear localization. ErbB2, a strong inducer of PKM2-Y105 phosphorylation, boosted nuclear localization of YAP and enhanced the cancer stem–like cell population. Treatment with the ErbB2 kinase inhibitor lapatinib decreased PKM2-Y105 phosphorylation and cancer stem–like cells, impeding PKM2 tumor-promoting function. Taken together, phosphorylation of PKM2-Y105 by activated kinases exerts oncogenic functions in part via activation of YAP downstream signaling to increase cancer stem–like cell properties. Significance: These findings reveal PKM2 promotes tumorigenesis by inducing cancer stem-like cell properties and clarify the paradox of PKM2's dichotomous functions in tumor progression.