mRNA translation is a therapeutic vulnerability necessary for bladder epithelial transformation.

Using genetically engineered mouse models, this work demonstrates that protein synthesis is essential for efficient urothelial cancer formation and growth but dispensable for bladder homeostasis. Through a candidate gene analysis for translation regulators implicated in this dependency, we discovered that phosphorylation of the translation initiation factor eIF4E at serine 209 is increased in both murine and human bladder cancer, and this phosphorylation corresponds with an increase in de novo protein synthesis. Employing an eIF4E serine 209 to alanine knock-in mutant mouse model, we show that this single posttranslational modification is critical for bladder cancer initiation and progression, despite having no impact on normal bladder tissue maintenance. Using murine and human models of advanced bladder cancer, we demonstrate that only tumors with high levels of eIF4E phosphorylation are therapeutically vulnerable to eFT508, the first clinical-grade inhibitor of MNK1 and MNK2, the upstream kinases of eIF4E. Our results show that phospho-eIF4E plays an important role in bladder cancer pathogenesis, and targeting its upstream kinases could be an effective therapeutic option for bladder cancer patients with high levels of eIF4E phosphorylation.

Targeting the Ca2+/Calmodulin-dependent protein kinase II by Tetrandrine in human liver cancer cells.

Hepatocellular carcinoma (HCC) is the most prevalent malignancy in liver and a leading cause of cancer-related deaths. Despite the pressing need for treatment options, patients with HCC develop significant resistance and adverse side effects to current approved drugs that becomes a major barrier to effective treatment. A natural product Tetrandrine (TET) is a potential alternative treatment option for HCC, with demonstrated effectiveness and low toxicity. However, the mechanisms by which Tetrandrine inhibits HCC are unclear. In the current study, we identify Ca2+/calmodulin-dependent protein kinase II δ (CaMKIIδ) as a potential TET drug target through structural modeling. Screening of a panel of HCC cell lines reveal differential sensitivities toward TET treatment. Interestingly, IC50 of TET inhibition of HCC cell proliferation is positively correlated with CaMKIIδ expression level in these distinct HCC cells. Furthermore, TET treatment resulted in a marked reduction of CaMKIIδ phosphorylation level, and knockdown of CaMKIIδ reduced the sensitivity of HCC cells to TET. Most importantly, CaMKIIδ protein levels in high-grade human HCC samples were significantly elevated as compared to normal liver tissues. Taken together, our studies demonstrate that the natural compound TET targets CaMKIIδ in HCC cells, and that CaMKIIδ level is a potential biomarker to identify HCC patient populations sensitive to Tetrandrine treatment.

Reduced T-dependent humoral immunity in CD20-deficient mice.

CD20 is a tetraspanning membrane protein expressed on B lymphocytes. CD20 deficiency in both mice and humans has recently been shown to have deleterious effects on Ab responses to T-independent Ags; however, no effect on T-dependent immunity has been reported. In this study, we used a Cd20⁻/⁻ mouse line to evaluate Ab responses to adeno-associated virus and SRBCs. The neutralizing Ab response to adeno-associated virus was significantly reduced by CD20 deficiency; both primary (IgM) and secondary (IgG1 and IgG2b) responses to SRBC were also reduced in Cd20⁻/⁻ mice, and this was associated with a reduction in the number of germinal center B cells. A successful humoral response requires the integration of intracellular signaling networks that critically rely on calcium mobilization. In this article, we confirm that BCR-mediated calcium mobilization is reduced in Cd20⁻/⁻ murine B cells after BCR stimulation in vitro, and further show that the reduction is due to an effect on calcium influx rather than calcium release from intracellular stores. Calcium-dependent upregulation of CD69 was impaired in CD20-deficient B cells, as was upregulation of CD86. Altogether, this study demonstrates a role for CD20 in B cell activation and T-dependent humoral immunity.