Durable complete response to pembrolizumab in microsatellite stable colorectal cancer

Revealing the mechanisms and therapeutic potential of immune checkpoint proteins across diverse protein families

Host immune responses to antigens are tightly regulated through the activation and inhibition of synergistic signaling networks that maintain homeostasis. Stimulatory checkpoint molecules initiate attacks on infected or tumor cells, while inhibitory molecules halt the immune response to prevent overreaction and self-injury. Multiple immune checkpoint proteins are grouped into families based on common structural domains or origins, yet the variability within and between these families remains largely unexplored. In this review, we discuss the current understanding of the mechanisms underlying the co-suppressive functions of CTLA-4, PD-1, and other prominent immune checkpoint pathways. Additionally, we examine the IgSF, PVR, TIM, SIRP, and TNF families, including key members such as TIGIT, LAG-3, VISTA, TIM-3, SIRPα, and OX40. We also highlight the unique dual role of VISTA and SIRPα in modulating immune responses under specific conditions, and explore potential immunotherapeutic pathways tailored to the distinct characteristics of different immune checkpoint proteins. These insights into the unique advantages of checkpoint proteins provide new directions for drug discovery, emphasizing that emerging immune checkpoint molecules could serve as targets for novel therapies in cancer, autoimmune diseases, infectious diseases, and transplant rejection.

Evaluation of the efficacy and safety of first- and second-line immunotherapy in patients with metastatic colorectal cancer: a systematic review and network meta-analysis based on randomized controlled trials

Background

A multitude of randomized controlled trials (RCTs) conducted in both the initial and subsequent treatment settings for patients diagnosed with metastatic colorectal cancer (mCRC) have provided clinical evidence supporting the efficacy of immunotherapy with the use of immune checkpoint inhibitors (ICIs). In light of these findings, the U.S. Food and Drug Administration (FDA) has authorized the use of several ICIs in specific subpopulations of mCRC patients. Nevertheless, there remains a dearth of direct comparative RCTs evaluating various treatment options. Consequently, the most effective ICI therapeutic strategy for microsatellite-stable (MSS) subgroup and microsatellite instability (MSI) subgroup in the first- and second-line therapies remains undefined. To address this gap, the present study employs a Bayesian network meta-analysis to ascertain the most effective first- and second-line ICI therapeutic strategies.

Methods

A comprehensive literature search was conducted across multiple databases, including PubMed, EMBASE, Cochrane Library, and Web of Science, with the retrieval date ranging from the databases' inception to August 20, 2024. A total of 875 studies were identified, and seven were ultimately included in the analysis after a screening process. A systematic review and network meta-analysis were conducted on the basis of the search results.

Results

This comprehensive analysis, comprising seven RCTs, evaluated first-line and second-line immunotherapy regimens in 1,358 patients diagnosed with mCRC. The treatments under investigation consisted of five initial treatments, including three focusing on MSS patients and two on MSI patients, as well as two secondary immunotherapy regimens, both focusing on MSS patients. A total of 1051 individuals underwent first-line treatment, while 307 received second-line treatment. The application of ICIs proved to offer varying degrees clinical benefits when compared to standard-of-care therapy alone, both in two subgroups of the first and the second treatment phases. Of particular note is the performance of Nivolumab combination with ipilimumab, which demonstrated superior efficacy in improving progression-free survival (PFS) (HR=0.21; 95% CI, 0.13-0.34),. Moreover, the treatment demonstrated an optimal safety profile, with a relatively low risk of adverse events (OR = 0.33; 95% CI, 0.19-0.56), compared to other first-line treatment modalities for MSI subgroup. Regarding MSS subgroup, the improvement of PFS by Nivolumab plus standard-of-care (SOC) was relatively significant (HR = 0.74; 95% CI, 0.53-1.02). In the realm of second-line therapies for MSS subgroup, the administration of Atezolizumab plus SOC has proven to be an effective approach for prolonging PFS, exhibiting an HR of 0.66 (95% CI, 0.44-0.99). These findings underscore the clinical benefits and safety profiles of ICIs in the treatment of mCRC across various treatment lines.

Conclusions

The clinical application of ICIs in both first- and second-line treatment strategies for patients with mCRC yields substantial therapeutic benefits. A detailed assessment in this study indicates that first-line treatment with Nivolumab combination with ipilimumab may represent an efficacious and well-tolerated therapeutic approach for MSI subgroup. In terms of MSS subgroup in first-line therapy, Nivolumab plus SOC may be a relative superior choice. In the context of second-line therapy for MSS subgroup, it is evident that a combination of Atezolizumab and SOC represents a preferable option for enhancing PFS. Furthermore, it is noteworthy that other ICIs treatment regimens also exhibit great value in various aspects, with the potential to inform the development of future clinical treatment guidelines and provide a stronger rationale for the selection of ICIs in both first- and second-line therapeutic strategies for mCRC.

Systematic review registration

https://www.crd.york.ac.uk/prospero/#recordDetails, identifier CRD42024543400.

Tumor mutational burden in colorectal cancer: Implications for treatment

Although immune checkpoint inhibitors have revolutionized the treatment of several advanced solid cancers, in colorectal cancer, the transformative benefit of these innovative medicines is currently limited to those with deficient mismatch repair or high microsatellite instability. Tumor mutational burden (TMB) has emerged as a potential predictor of immunotherapy benefit, but the lack of standardization in its assessment and reporting has hindered the introduction of this biomarker in routine clinical practice. Here, we compiled 45 colorectal cancer studies utilizing numerical thresholds for high-TMB. In this group of studies, TMB cut-offs ranged from 6.88 to 41 mut/Mb and were most often set at 10, 17, or 20 mut/Mb. Additionally, we observed divergent TMB definitions and inconsistent disclosure of specific methodological details, which collectively emphasize the substantial lack of harmonization within the field. Ongoing efforts to harmonize TMB assessment will be critical to validate TMB as a predictive marker of immunotherapy response.

Characterisation of tumor microenvironment and prevalence of CD274/PD-L1 genetic alterations difference in colorectal Cancer

BACKGROUND

Large-scale genomic alterations, especially CD274/PD-L1 gene amplification, have great impact on anti-PD-1 efficacy on cancers such as Hodgkin's lymphoma. However, the prevalence of PD-L1 genetic alterations in colorectal cancer (CRC) and its correlation with the tumor immune microenvironment and clinical implications remain unknown.

MATERIALS AND METHODS

PD-L1 genetic alterations were evaluated in 324 patients with newly diagnosed CRC including 160 mismatch repair-deficient (dMMR) patients and 164 mismatch repair-proficient (pMMR) patients using fluorescence in situ hybridization (FISH) method. The correlation between PD-L1 and the expression of the common immune markers was analyzed.

RESULTS

Totally 33 (10.2%) patients were identified with aberrant PD-L1 genetic alternations including deletion (2.2%), polysomy (4.9%), and amplification (3.1%); They had more aggressive features such as advanced stage (P = 0.02), shorter overall survival (OS) (P < 0.001) than patients with disomy. The aberrations correlated with positive lymph node (PLN) (p = 0.001), PD-L1 expression by immunohistochemistry (IHC) in tumor cells (TCs) or tumor-infiltrated immunocytes (ICs) (both p < 0.001), and pMMR (p = 0.029). When dMMR and pMMR were analyzed independently, the correlations of aberrant PD-L1 genetic alterations with PD-1 expression (p = 0.016), CD4 + T cells (p = 0.032), CD8 T + cells (p = 0.032) and CD68 + cells (p = 0.04) were only found in dMMR cohort.

CONCLUSIONS

The prevalence of PD-L1 genetic alterations was relatively low in CRC, but the aberrations usually correlate with aggressive nature. The correlation between PD-L1 genetic alterations and tumor immune features was only observed in dMMR CRC.