Targeted literature review on use of tumor mutational burden status and programmed cell death ligand 1 expression to predict outcomes of checkpoint inhibitor treatment.

BACKGROUND: To achieve optimal outcomes, an individual approach is needed in the treatment and care of patients. The potential value of tumor mutational burden (TMB) status and/or programmed cell death ligand 1 (PD-L1) expression as biomarkers to predict which patients are most likely to respond to checkpoint inhibitors has been explored in many studies. The goal of this targeted literature review is to identify data available for TMB status and/or PD-L1 expression that predict response to checkpoint inhibitors and/or anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies. METHODS: Targeted literature searches were performed using electronic medical databases (MEDLINE, Embase, and BIOSIS) and internet searches of specified sites. Bibliographies of key systematic literature reviews and meta-analyses also were reviewed for studies of interest. RESULTS: The review identified 27 studies of non-small cell lung cancer (NSCLC), 40 studies of melanoma, 10 studies of urothelial cancer, and 5 studies of renal cell cancer indications. Studies also were identified in other cancer types, e.g., colorectal, breast, gastric, and Merkel cell cancer and squamous-cell carcinoma of the head and neck. Twelve trials, including six in NSCLC and four in melanoma, evaluated TMB as a predictor of outcomes. A TMB of ≥10 mutations per megabase was shown to be an effective biomarker in the CheckMate 227 study. PD-L1 expression was included in the majority of identified studies and was found to predict response in in melanoma and in all types of NSCLC. Prediction of response was not a prespecified analysis in some studies; others had small sample sizes and wide confidence intervals. A clear predictive trend for PD-L1 expression was not identified in renal, breast, gastric, or Merkel cell cancer. CONCLUSION: Based on data contained in this review, assessment of TMB status and PD-L1 expression may help enhance the prediction of response to checkpoint inhibition in some tumors, such as NSCLC and melanoma. In this rapidly growing area of research, further exploratory biomarkers are being investigated including tumor-infiltrating lymphocytes, immune profiling (e.g., effector T cells or regulatory T cells), epigenetic signatures, T-cell receptor repertoire, proteomics, microbiome, and metabolomics.

Meta-analysis of bismuth quadruple therapy versus clarithromycin triple therapy for empiric primary treatment of Helicobacter pylori infection.

BACKGROUND: In areas with high clarithromycin resistance, bismuth quadruple therapy (BQT) is recommended instead of clarithromycin triple therapy (CTT) as the first-line treatment for Helicobacter pylori eradication. METHODS: Randomized clinical trials (RCTs) comparing BQT to CTT were identified through electronic and manual searches. A meta-analysis was performed to compare the efficacy and tolerability of these two regimens as first-line treatments for H. pylori infection. The effect of antibiotic resistance on treatment efficacy was also analyzed. RESULTS: Twelve RCTs were included. BQT achieved eradication in 77.6% of patients, whereas CTT achieved an eradication rate of 68.9% [risk difference (RD) = 0.06, 95% CI: -0.01/0.13]. A high heterogeneity among the trials was found (χ2 = 50.16, p < 0.00001; I2 = 78%). In the subgroup analysis for treatment duration, the 10-day BQT was more effective than the 7-day CTT (RD = 0.25, 95% CI: 0.18/0.32), whereas no differences were observed between CTT and BQT given for 7 or 10 days. There were no statistical differences in side effects and compliance between both therapies (RD = 0.92, 95% CI: 0.76/1.12, and RD = -0.03, 95% CI: -0.05/0.00, respectively). The effect of antibiotic resistance on eradication rates was reported in 4 of the 12 RCTs. Clarithromycin resistance significantly affected the efficacy of CTT (RD = 0.75, 95% CI: 0.63/0.87), whereas BQT efficacy was not affected by metronidazole resistance (RD = 0.09, 95% CI: -0.06/0.25). CONCLUSIONS: The 10-day BQT was more effective than the 7-day CTT as a first-line therapy for H. pylori infection, whereas BQT and CTT for 7 or 10 days yielded similar eradication rates. Compliance and side effect rates were similar for both therapies. BQT overcomes clarithromycin resistance and its efficacy is not affected by metronidazole resistance.

The transmembrane adaptor protein SIT inhibits TCR-mediated signaling.

Transmembrane adaptor proteins (TRAPs) organize signaling complexes at the plasma membrane, and thus function as critical linkers and integrators of signaling cascades downstream of antigen receptors. We have previously shown that the transmembrane adaptor protein SIT regulates the threshold for thymocyte selection. Moreover, T cells from SIT-deficient mice are hyperresponsive to CD3 stimulation and undergo enhanced lymphopenia-induced homeostatic proliferation, thus indicating that SIT inhibits TCR-mediated signaling. Here, we have further addressed how SIT regulates signaling cascades in T cells. We demonstrate that the loss of SIT enhances TCR-mediated Akt activation and increased phosphorylation/inactivation of Foxo1, a transcription factor of the Forkhead family that inhibits cell cycle progression and regulates T-cell homeostasis. We have also shown that CD4(+) T cells from SIT-deficient mice display increased CD69 and CD40L expression indicating an altered activation status. Additional biochemical analyses further revealed that suppression of SIT expression by RNAi in human T cells resulted in an enhanced proximal TCR signaling. In summary, the data identify SIT as an important modulator of TCR-mediated signaling that regulates T-cell activation, homeostasis and tolerance.

Regulation of T cell homeostasis by the transmembrane adaptor protein SIT.

The transmembrane adaptor protein SIT is a negative regulator of TCR-mediated signaling. However, little is known about the functional role of SIT in mature T cells. In this study, we show that mice deficient for SIT display a decreased number of naive CD8(+) T cells and a progressive accumulation of memory-like (CD44(high)) CD8(+) T lymphocytes that resemble cells undergoing homeostatic proliferation. Indeed, when transferred into lymphopenic hosts, SIT(-/-) naive CD8(+) T cells undergo enhanced homeostatic proliferation and express a higher level of CD44 in comparison to wild-type T cells. By using class-I-restricted TCR transgenic models with different ligand affinity/avidity, we show that lymphopenia-induced homeostatic proliferation is more pronounced in cells carrying low-affinity TCRs. Strikingly, the loss of SIT induces homeostatic proliferation of HY TCR transgenic cells, which are normally unable to proliferate in lymphopenic mice. Collectively, these data demonstrate that SIT negatively regulates T cell homeostasis. Finally, we show that SIT-deficient T cells develop a mechanism analogous to sensory adaptation as they up-regulate CD5, down-regulate the coreceptor, and display impaired TCR-mediated ZAP-70 activation.