Chen, Yuping

AbstractObjectiveTo elucidate the relationship between USP19 and O(6)‐methylguanine‐DNA methyltransferase (MGMT) after temozolomide treatment in glioblastoma (GBM) patients with chemotherapy resistance.MethodsScreening the deubiquitinase pannel and identifying the deubiquitinase directly interacts with and deubiquitination MGMT. Deubiquitination assay to confirm USP19 deubiquitinates MGMT. The colony formation and tumor growth study in xenograft assess USP19 affects the GBM sensitive to TMZ was performed by T98G, LN18, U251, and U87 cell lines. Immunohistochemistry staining and survival analysis were performed to explore how USP19 is correlated to MGMT in GBM clinical management.ResultsUSP19 removes the ubiquitination of MGMT to facilitate the DNA methylation damage repair. Depletion of USP19 results in the glioblastoma cell sensitivity to temozolomide, which can be rescued by overexpressing MGMT. USP19 is overexpressed in glioblastoma patient samples, which positively correlates with the level of MGMT protein and poor prognosis in these patients.ConclusionThe regulation of MGMT ubiquitination by USP19 plays a critical role in DNA methylation damage repair and GBM patients’ temozolomide chemotherapy response.

Abstract The Warburg effect released lactate promotes cancer progression, but the mechanisms remain unclear. Here, we found lactate activated MAPK pathway through ERK-lactylation to promote cancer progression. Moreover, we identified the GCN5 as the lactyl-transferase for ERK lactylation. Interestingly, activated ERK phosphorylated GCN5 and promoted GCN5 lactyl-transferase activity for ERK, which formed the positive feedback loop to facilitate lactate-mediated cancer progression. Mechanistically, ERK-K231 lactylation decreased the dissociation energy between ERK and MEK, due to the reduced electrostatic interaction between ERK-K231 and MEK-D217. This facilitated the dissociation of ERK from MEK kinases, which in turn induced ERK dimerization and activation. Hence, we developed a cell-penetrating peptide to specifically inhibit the ERK lactylation, and demonstrated the peptide impaired the tumor growth with KRAS-mutant. Taken together, we define a molecular mechanism that lactate accelerates cancer progression through ERK-GCN5 lactylation-phosphorylation cascade and provide a strategy to target ERK lactylation, especially for RAS-MAPK-driven cancers.

The EGFR-RAS-ERK pathway is one of the most important signaling cascades in cell survival, growth, and proliferation. Aberrant activation of this pathway is a common mechanism in various cancers. Here, we report that CDK2 is a novel regulator of the ERK pathway via USP37 deubiquitinase (DUB). Mechanistically, CDK2 phosphorylates USP37, which is required for USP37 DUB activity. Further, USP37 deubiquitinates and stabilizes ERK1/2, thereby enhancing cancer cell proliferation. Thus, CDK2 is able to promote cell proliferation by activating USP37 and, in turn, stabilizing ERK1/2. Importantly, combined CDK1/2 and EGFR inhibitors have a synergetic anticancer effect through the downregulation of ERK1/2 stability and activity. Indeed, our patient-derived xenograft (PDX) results suggest that targeting both ERK1/2 stability and activity kills cancer cells more efficiently even at lower doses of these two inhibitors, which may reduce their associated side effects and indicate a potential new combination strategy for cancer therapy.

Abstract The human RecQ helicase BLM is involved in the DNA damage response, DNA metabolism, and genetic stability. Loss of function mutations in BLM cause the genetic instability/cancer predisposition syndrome Bloom syndrome. However, the molecular mechanism underlying the regulation of BLM in cancers remains largely elusive. Here, we demonstrate that the deubiquitinating enzyme USP37 interacts with BLM and that USP37 deubiquitinates and stabilizes BLM, thereby sustaining the DNA damage response (DDR). Mechanistically, DNA double-strand breaks (DSB) promotes ATM phosphorylation of USP37 and enhances the binding between USP37 and BLM. Moreover, knockdown of USP37 increases BLM polyubiquitination, accelerates its proteolysis, and impairs its function in DNA damage response. This leads to enhanced DNA damage and sensitizes breast cancer cells to DNA-damaging agents in both cell culture and in vivo mouse models. Collectively, our results establish a novel molecular mechanism for the USP37–BLM axis in regulating DSB repair with an important role in chemotherapy and radiotherapy response in human cancers.

We clarify that DNA damage triggers autophagy by CHK2-FOXK axis, and misregulation of this pathway leads to chemoresistance.