Colorectal Cancer Immunotherapy: State of the Art and Future Directions

The tumor microenvironment and dendritic cells: Developers of pioneering strategies in colorectal cancer immunotherapy?

Colorectal cancer (CRC) is the world's third most frequent cancer, and both its incidence and fatality rates are rising. Despite various therapeutic approaches, neither its mortality rate nor its recurrence frequency has decreased significantly. Additionally, conventional treatment approaches, such as chemotherapy and radiotherapy, have several side effects and risks for patients with CRC. Accordingly, the need for alternative and effective treatments for CRC patients is critical. Immunotherapy that utilizes dendritic cells (DCs) harnesses the patient's immune system to combat cancer cells effectively. DCs are the most potent antigen-presenting cells (APCs), which play a vital role in generating anti-cancer T cell responses. A significant barrier to the immune system's ability to eliminate CRC is the establishment of a potent immunosuppressive tumor milieu by malignant cells. Since DCs are frequently defective in this milieu, the tumor setting significantly reduces the effectiveness of DC-based therapy. Determining central mechanisms contributing to tumor growth by unraveling and comprehending the interaction between CRC tumor milieu and DCs may lead to new therapeutic approaches. This study aims to review DC biology and discuss its role in T-cell-mediated anti-tumor immunity, as well as to highlight the immunosuppressive effects of the CRC tumor milieu on the function of DCs. We will also highlight the tumor microenvironment (TME)-related factors that interfere with DC function as a possible therapeutic target to enhance DC-based cell therapy efficacy.

Combined delivery of IL12 and an IL18 mutant without IL18BP-binding activity by an adenoviral vector enhances tumor specific immunity

Cytokines play pivotal roles in anticancer immune response. We previously reported that adenovirus armed with an IL18 variant (DR18) that overcomes IL18BP neutralizing effect displayed powerful therapeutic effects in local and distant tumors when delivered intratumorally. Here, we tested a combined delivery of IL12 and DR18 in tumor models since IL12 and IL18 are known to act synergistically in potentiating IFNγ production and antitumor immunity. To minimize adverse effects associated with systemic delivery, we constructed oncolytic adenoviruses (oAd) harboring DR18 and IL12 (oAd.DR18/IL12). IL12 was expressed as a single chain IL12 (scIL12) peptide composed of the IL12/p40 and IL12/p35 subunits. Intratumoral administration of oAd.DR18/IL12, oAd-expressing DR18 (oAd.DR18), or oAd-expressing IL12 (oAd.IL12) showed antitumor effect in syngeneic colorectal tumor models. Compared to oAd.DR18 or oAd.IL12, administration of oAd.DR18/IL12 improved the antitumor effects as well as increased survival rate in these models. We detected enhanced tumor infiltrating T lymphocytes and NK cells in oAd.DR18/IL12-treated mice than those from mock-treated or individually treated groups. Moreover, mice received oAd.DR18/IL12 had more robust tumor-specific cytotoxicity. Importantly, mice that had tumor regression after oAd.DR18/IL12 treatment established anti-tumor specific immune memory. These results show that adenovirus armed with engineered cytokines boosts tumor specific immunity and antitumor effect.

Inhibition of Glutamate-to-Glutathione Flux Promotes Tumor Antigen Presentation in Colorectal Cancer Cells

Colorectal cancer (CRC) cells display remarkable adaptability, orchestrating metabolic changes that confer growth advantages, pro-tumor microenvironment, and therapeutic resistance. One such metabolic change occurs in glutamine metabolism. Colorectal tumors with high glutaminase (GLS) expression exhibited reduced T cell infiltration and cytotoxicity, leading to poor clinical outcomes. However, depletion of GLS in CRC cells has minimal effect on tumor growth in immunocompromised mice. By contrast, remarkable inhibition of tumor growth is observed in immunocompetent mice when GLS is knocked down. It is found that GLS knockdown in CRC cells enhanced the cytotoxicity of tumor-specific T cells. Furthermore, the single-cell flux estimation analysis (scFEA) of glutamine metabolism revealed that glutamate-to-glutathione (Glu-GSH) flux, downstream of GLS, rather than Glu-to-2-oxoglutarate flux plays a key role in regulating the immune response of CRC cells in the tumor. Mechanistically, inhibition of the Glu-GSH flux activated reactive oxygen species (ROS)-related signaling pathways in tumor cells, thereby increasing the tumor immunogenicity by promoting the activity of the immunoproteasome. The combinatorial therapy of Glu-GSH flux inhibitor and anti-PD-1 antibody exhibited a superior tumor growth inhibitory effect compared to either monotherapy. Taken together, the study provides the first evidence pointing to Glu-GSH flux as a potential therapeutic target for CRC immunotherapy.

Advancements in immunotherapy for colorectal cancer treatment: a comprehensive review of strategies, challenges, and future prospective

PURPOSE

Colorectal cancer (CRC) remains one of the leading causes of cancer-related mortality worldwide. Metastatic colorectal cancer (mCRC) continues to present significant challenges, particularly in patients with proficient mismatch repair/microsatellite stable (pMMR/MSS) tumors. This narrative review aims to provide recent developments in immunotherapy for CRC treatment, focusing on its efficacy and challenges.

METHODS

This review discussed the various immunotherapeutic strategies for CRC treatment, including immune checkpoint inhibitors (ICIs) targeting PD-1 and PD-L1, combination therapies involving ICIs with other modalities, chimeric antigen receptor T-cell (CAR-T) cell therapy, and cancer vaccines. The role of the tumor microenvironment and immune evasion mechanisms was also explored to understand their impact on the effectiveness of these therapies.

RESULTS

This review provides a comprehensive update of recent advancements in immunotherapy for CRC, highlighting the potential of various immunotherapeutic approaches, including immune checkpoint inhibitors, combination therapies, CAR-T therapy, and vaccination strategies. The results of checkpoint inhibitors, particularly in patients with MSI-H/dMMR tumors, which have significant improvements in survival rates have been observed. Furthermore, this review also addresses the challenges faced in treating pMMR/MSS CRC, which remains resistant to immunotherapy.

CONCLUSION

Immunotherapy plays a significant role in the treatment of CRC, particularly in patients with MSI-H/dMMR tumors. However, many challenges remain, especially in treating pMMR/MSS CRC. This review discussed the need for further research into combination therapies, biomarker development, CAR-T cell therapy, and a deeper understanding of immune evasion mechanisms for CRC treatment.

Evaluation of blood MSI burden dynamics to trace immune checkpoint inhibitor therapy efficacy through the course of treatment

Analysis of serial liquid biopsy (LB) samples has been found to be a promising approach for the monitoring of tumor dynamics in the course of therapy for patients with colorectal cancer (CRC). Currently, somatic mutations are used for tracing the dynamics of the tumor via LB. However, the analysis of the dynamic changes in the molecular signatures such as microsatellite instability (MSI) is not currently used. We hypothesized that changes in blood MSI burden (bMSI) could be registered using serial LB sampling in the course of immune checkpoint inhibitors (ICI), and that its changes could potentially correlate with treatment outcomes. We report the preliminary findings of the observational trial launched to study (NCT06414304) the dynamics of bMSI in 9 MSI-positive CRC patients receiving ICI. NGS-based MSI testing was performed on both pre-treatment FFPE and serial LB samples. For patients who had detectable bMSI burden in any of the LB samples (n = 8, 89%), median bMSI was 1.4% (range, 0.01-40%). Among patients with detectable MSI in available FFPE samples, median MSI burden was 29.3% (range, 10-40%). bMSI detected in baseline LB and FFPE samples were positively correlated (Pearson's R 0.47). Maximal variant allele frequencies of driver mutations observed in LB were also positively correlated with bMSI burden (Pearson's R 0.7). Patients who had clinical benefit had undetectable bMSI burden at follow-up. Our results provide the rationale for further validation of bMSI as a predictive biomarker of ICI in MSI-positive patients.

[Genetic drivers for inflammatory protein markers in colorectal cancer: a Mendelian randomization approach to clinical prognosis study]

OBJECTIVE

To explore the causal relationship between inflammatory protein markers and the risk of colorectal cancer using a Mendelian randomization (MR) approach.

METHODS

We obtained data pertaining to colorectal cancer from Genome-Wide Association Study (GWAS) datasets and used 91 inflammatory protein markers as the exposure variables. A two-sample MR analysis model was used to assess the causal link between the inflammatory markers and colorectal cancer risk. The robustness of the results was evaluated through heterogeneity, pleiotropy, and sensitivity analyses using 5 MR models: Inverse Variance Weighted (IVW), Weighted Median, MR Egger, Simple Mode, and Weighted Mode. We examined the mRNA expressions of PD-L1, AXIN1, and β-NGF using RT-qPCR in 86 untreated patients with colorectal adenocarcinoma admitted in Nanfang Hospital between December, 2021 and December 2023, and analyzed their correlation with the clinical characteristics of the patients.

RESULTS

Using the IVW model, MR analysis revealed significant causal associations between a reduced risk of colorectal cancer and lowered expressions of AXIN1 (OR=0.866, 95% CI: 0.754-0.994, P=0.040), β-NGF (OR=0.914, 95% CI: 0.843-0.990, P=0.028; OR=0.884, 95% CI: 0.784-0.998, P=0.047 using Weighted Median model), and PD-L1 (OR=0.903, 95% CI: 0.824- 0.989, P=0.028). No significant heterogeneity or pleiotropy was observed, indicating good stability of the results. Sensitivity analysis confirmed the reliability of the findings. The clinical study demonstrated a significant correlation between PD-L1 expression and TNM staging, particularly in stage Ⅳ patients (P=0.007). AXIN1 and β -NGF expression levels were significantly correlated with the degree of tumor differentiation, and their expressions were higher in poorly differentiated samples (P<0.001).

CONCLUSION

Lowered expressions of inflammatory protein markers AXIN1, β-NGF, and PD-L1 are causally correlated with a reduced risk of colorectal cancer and their expression levels are associated with TNM staging and tumor differentiation. These markers may thus serve as potential targets for colorectal cancer treatment and prevention.

HIPK2 in Colon Cancer: A Potential Biomarker for Tumor Progression and Response to Therapies

Colon cancer, one of the most common and fatal cancers worldwide, is characterized by stepwise accumulation of specific genetic alterations in tumor suppressor genes or oncogenes, leading to tumor growth and metastasis. HIPK2 (homeodomain-interacting protein kinase 2) is a serine/threonine protein kinase and a "bona fide" oncosuppressor protein. Its activation inhibits tumor growth mainly by promoting apoptosis, while its inactivation increases tumorigenicity and resistance to therapies of many different cancer types, including colon cancer. HIPK2 interacts with many molecular pathways by means of its kinase activity or transcriptional co-repressor function modulating cell growth and apoptosis, invasion, angiogenesis, inflammation and hypoxia. HIPK2 has been shown to participate in several molecular pathways involved in colon cancer including p53, Wnt/β-catenin and the newly identified nuclear factor erythroid 2 (NF-E2) p45-related factor 2 (NRF2). HIPK2 also plays a role in tumor-host interaction in the tumor microenvironment (TME) by inducing angiogenesis and cancer-associated fibroblast (CAF) differentiation. The aim of this review is to assess the role of HIPK2 in colon cancer and the underlying molecular pathways for a better understanding of its involvement in colon cancer carcinogenesis and response to therapies, which will likely pave the way for novel colon cancer therapies.

Current and Future Trends of Colorectal Cancer Treatment: Exploring Advances in Immunotherapy

Cancer of the colon and rectum (CRC) has been identified among the three most prevalent types of cancer and cancer-related deaths for both sexes. Even though significant progress in surgical and chemotherapeutic techniques has markedly improved disease-free and overall survival rates in contrast to those three decades ago, recent years have seen a stagnation in these improvements. This underscores the need for new therapies aiming to augment patient outcomes. A number of emerging strategies, such as immune checkpoint inhibitors (ICIs) and adoptive cell therapy (ACT), have exhibited promising outcomes not only in preclinical but also in clinical settings. Additionally, a thorough appreciation of the underlying biology has expanded the scope of research into potential therapeutic interventions. For instance, the pivotal role of altered telomere length in early CRC carcinogenesis, leading to chromosomal instability and telomere dysfunction, presents a promising avenue for future treatments. Thus, this review explores the advancements in CRC immunotherapy and telomere-targeted therapies, examining potential synergies and how these novel treatment modalities intersect to potentially enhance each other's efficacy, paving the way for promising future therapeutic advancements.

Redefining the battle against colorectal cancer: a comprehensive review of emerging immunotherapies and their clinical efficacy

Colorectal cancer (CRC) is the third most common cancer globally and presents a significant challenge owing to its high mortality rate and the limitations of traditional treatment options such as surgery, radiotherapy, and chemotherapy. While these treatments are foundational, they are often poorly effective owing to tumor resistance. Immunotherapy is a groundbreaking alternative that has recently emerged and offers new hope for success by exploiting the body's own immune system. This article aims to provide an extensive review of clinical trials evaluating the efficacy of various immunotherapies, including CRC vaccines, chimeric antigen receptor T-cell therapies, and immune checkpoint inhibitors. We also discuss combining CRC vaccines with monoclonal antibodies, delve into preclinical studies of novel cancer vaccines, and assess the impact of these treatment methods on patient outcomes. This review seeks to provide a deeper understanding of the current state of CRC treatment by evaluating innovative treatments and their potential to redefine the prognosis of patients with CRC.