Mechanistic insights into the allosteric inactivation mechanism of ZAP-70 induced by the hot spot W165C mutation.

Zeta chain-associated protein kinase 70 (ZAP-70) is a non-receptor tyrosine kinase that interacts with the activated T-cell receptor to transduce downstream signals, and thus plays an important role in the adaptive immune system. The biphosphorylated immunotyrosine-based activation motifs (ITAM-Y2P) binds to the N-SH2 and C-SH2 domains of ZAP-70 to promote the activation of ZAP-70. The present study explores molecular mechanisms of allosteric inactivation of ZAP-70 induced by the hot spot W165C mutation through atomically detailed molecular dynamics simulation approaches. We report microsecond-length simulations of two states of the tandem SH2 domains of ZAP-70 in complex with the ITAM-Y2P motif, including the wild-type and W165C mutant. Extensive analysis of local flexibility and dynamical correlated motions show that W165C mutation changes coupled motions of protein domains and community networks. The binding affinities of the ITAM-Y2P motif to the wild-type and W165C mutant of ZAP-70 are predicted using binding free energy calculations. The results suggest that the driving force to decrease the binding affinity in the W165C mutant derives from the difference in the protein-protein electrostatic interactions. Moreover, the per-residue free energy decomposition unravels that the contributions from residues in the phosphorylated Tyr315 (pY315) binding site, in particular pY315 of ITAM-Y2P, and Arg43, Tyr240 of ZAP-70, are the key determinants for the loss of binding affinity. This study may insights into our understanding of the pathological mechanism of ZAP-70.Communicated by Ramaswamy H. Sarma.

N6-Methyladenosine-Mediated Up-Regulation of FZD10 Regulates Liver Cancer Stem Cells' Properties and Lenvatinib Resistance Through WNT/ß-Catenin and Hippo Signaling Pathways.

BACKGROUND & AIMS: Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide, but there is a deficiency of early diagnosis biomarkers and therapeutic targets. Drug resistance accounts for most HCC-related deaths, yet the mechanisms underlying drug resistance remain poorly understood. METHODS: Expression of Frizzled-10 (FZD10) in liver cancer stem cells (CSCs) was identified by means of RNA sequencing and validated by means of real-time polymerase chain reaction and immunohistochemistry. In vitro and in vivo experiments were used to assess the effect of FZD10 on liver CSC expansion and lenvatinib resistance. RNA sequencing, RNA binding protein immunoprecipitation, and luciferase report assays were applied to explore the mechanism underlying FZD10-mediated liver CSCs expansion and lenvatinib resistance. RESULTS: Activation of FZD10 in liver CSCs was mediated by METTL3-dependent N6-methyladenosine methylation of FZD10 messenger RNA. Functional studies revealed that FZD10 promotes self-renewal, tumorigenicity, and metastasis of liver CSCs via activating ß-catenin and YAP1. The FZD10-ß-catenin/YAP1 axis is activated in liver CSCs and predicts poor prognosis. Moreover, FZD10-ß-catenin/c-Jun axis transcriptionally activates METTL3 expression, forming a positive feedback loop. Importantly, the FZD10/ß-catenin/c-Jun/MEK/ERK axis determines the responses of hepatoma cells to lenvatinib treatment. Analysis of patient cohort, patient-derived tumor organoids, and patient-derived xenografts further suggest that FZD10 might predict lenvatinib clinical benefit in patients with HCC. Furthermore, treatment of lenvatinib-resistant HCC with adeno-associated virus targeting FZD10 or a ß-catenin inhibitor restored lenvatinib response. CONCLUSIONS: Elevated FZD10 expression promotes expansion of liver CSCs and lenvatinib resistance, indicating that FZD10 expression is a novel prognostic biomarker and therapeutic target for human HCC.

Single-cell RNA sequencing highlights the functional role of human endogenous retroviruses in gallbladder cancer.

BACKGROUND: Gallbladder cancer (GBC), the most common malignancy of the biliary tract, shows late diagnosis and low survival rate and requires continued search for new diagnostic biomarkers and therapeutic targets. Human endogenous retroviruses (HERVs) are specifically prone to be reactivated in diverse cancers and are implicated in cancer progression and immunotherapy. METHODS: Single-cell RNA sequencing was performed on tumor tissues and paired adjacent tissues from 4 GBC patients. Dual-luciferase reporter assay was applied to measure enhancer activity of HERV sequences. FINDINGS: We dissected the cellular diversity and described the HERV transcriptomic landscape for GBC. We found that HERVs were transcribed in a cell type-specific manner and different HERV families were associated with diverse biological effects. HERVs could function as enhancers, presumably causing altered expression of neighboring genes. The transcription level of HERVH was gradually elevated with the malignant transformation of epithelial cells, suggesting HERVH may be a potential early diagnostic biomarker of GBC. HHLA2, a newly emerging immune checkpoint, was derived by HERVH, exhibited an expressional correlation with HERVH, and was identified as a promising target for immunotherapy. INTERPRETATION: Exploring the transcriptional landscape and potential functional impact of HERVs highlights the important role of HERVs in GBC and provides a fresh perspective on managing GBC. FUNDING: This study was supported by the National Natural Science Foundation of China (31970176, 81972256) and the research grants from the Innovation Capacity Building Project of Jiangsu province (BM2020019).

Tumor suppressor LKB1 inhibits the progression of gallbladder carcinoma and predicts the prognosis of patients with this malignancy.

Gallbladder carcinoma (GBC) represents the most common fatal tumors of the biliary tract. The 3-year or 5-year survival rate for patients with this disease are 30 and 5%, respectively. Liver kinase B1 (LKB1), a primary upstream kinase of adenosine monophosphate-activated protein kinase (AMPK) necessary for maintaining cell metabolism and energy homeostasis, has been found to be an important tumor suppressor gene in recent years, and its inactivation has also found to be closely associated with tumor growth, metastasis and cancer stem cell (CSC) proliferation. Nevertheless, the function of LKB1 in GBC remains unclear. In this study, we found that the expression of LKB1 in GBC tissues was decreased compared with that in non-cancerous tissues. LKB1 overexpression suppressed the proliferation, metastasis and expansion of GBC CSCs. Mechanically, LKB1 suppressed GBC cell progression via the JAK/signal transducer and activator of transcription 3 (STAT3) pathway. The use of the JAK2 inhibitor, AZD­1480, attenuated the suppressive effects of LKB1 overexpression on the growth, metastasis and self-renewal ability of the GBC cells, which further demonstrated that JAK/STAT3 was involved in the LKB1-induced suppression of GBC cell growth, metastasis and self-renewal ability. More importantly, the decreased expression of LKB1 was a predictor of a poor prognosis of patients with GBC. On the whole, our data indicate that LKB1 inhibits GBC cell growth, metastasis and self-renewal ability by disrupting JAK/STAT3 signaling, and may thus prove to be a novel prognostic biomarker for patients with GBC.