A Cullin3-KLHL20 Ubiquitin Ligase-Dependent Pathway Targets PML to Potentiate HIF-1 Signaling and Prostate Cancer Progression

Abstract

Tumor hypoxia is associated with disease progression and treatment failure, but the hypoxia signaling mechanism is not fully understood. Here, we show that KLHL20, a Cullin3 (Cul3) substrate adaptor induced by HIF-1, coordinates with the actions of CDK1/2 and Pin1 to mediate hypoxia-induced PML proteasomal degradation. Furthermore, this PML destruction pathway participates in a feedback mechanism to maximize HIF-1α induction, thereby potentiating multiple tumor hypoxia responses, including metabolic reprogramming, epithelial-mesenchymal transition, migration, tumor growth, angiogenesis, and chemoresistance. In human prostate cancer, overexpression of HIF-1α, KLHL20, and Pin1 correlates with PML down-regulation, and hyperactivation of the PML destruction pathway is associated with disease progression. Our study indicates that the KLHL20-mediated PML degradation and HIF-1α autoregulation play key roles in tumor progression.

Ubiquitination of tumor suppressor PML regulates prometastatic and immunosuppressive tumor microenvironment

“…To identify novel PML ubiquitin ligases, we assayed PML ubiquitination in cells expressing a dominant-negative (DN) mutant of each CUL family protein. Consistent with our previous study (18), we found that CUL3-DN reduced PML ubiquitination. Interestingly, CUL4-DN elicited a similar effect ( Figure 1A).…”

“…Plasmids encoding Myc-ubiquitin, His-ubiquitin, Myc-CUL3, Myc-ROC1, Flag-PML-I, and Flag-PML-IV were described previously (18). WDR4 cDNA (39) was subcloned to pRK5 with a Myc-or V5-tag, and WDR4 mutants were generated by site-directed mutagenesis.…”

“…We assessed the protein expression of WDR4 and PML in a cohort of 120 lung cancer patients. Immunohistochemical analydegradation has been observed in a number of cancer types (14,(18)(19)(20)(21)(22), and the ubiquitin ligases cullin 3-kelch-like family member 20 (CUL3-KLHL20) and ubiquitin protein ligase E3A (E6AP) are responsible for PML destruction in certain cancer types (18,22). However, the ubiquitin ligase that mediates PML degradation in lung cancer remains elusive, and the molecular mechanism for PML degradation in tumors has not been completely understood.…”

Identification of RNF168 as a PML nuclear body regulator

“…A few ubiquitin E3 ligases have been reported to promote loss of PML under specific circumstances. For example, the KLHL20-Cul3-ROC1 complex downregulates PML in response to hypoxia (Yuan et al, 2011), and SIAH1 and SIAH2 can induce PML degradation upon overexpression (Fanelli et al, 2004). In addition, E6AP has been identified as a PML regulator in Burkitt's lymphoma (Wolyniec et al, 2012).…”

PML represses lung cancer metastasis by suppressing the nuclear EGFR-mediated transcriptional activation ofMMP2

“…9 Recently, it has been discovered that PML also plays a role in regulating cell migration through the transcriptional control of integrin b1 and the translational control of HIF1a. 10,11 In addition, PML plays important roles in regulating cancer stem cells. 12 Nevertheless, the role of PML in the process of lung cancer metastasis remains unclear.…”