Recurrent Frameshift Neoantigen Vaccine Elicits Protective Immunity With Reduced Tumor Burden and Improved Overall Survival in a Lynch Syndrome Mouse Model

Immunoprevention of non-viral cancers: challenges and strategies for early intervention

While the effects of cancer vaccines have been extensively studied in the therapeutic setting, research has been more limited in the areas of cancer prevention and interception. Although cancer prevention by vaccines has been possible for viral-mediated cancers, such as cervical cancers and hepatocellular carcinoma, preventing non-viral cancers by immunopreventive vaccines is challenging. Many tumors at late stages are less responsive to treatments, including immunotherapies and vaccines, in part due to an immunosuppressive microenvironment. Shifting the strategy to intervention at early stages of cancer development and progression and focusing on high-risk cohorts with defined molecular targets offers a pathway for improved vaccine efficacy. Current research on the role of immune mechanisms during tumor initiation and progression is rapidly evolving and recent emerging preclinical immunoprevention studies have shown that vaccines can induce host immune response and effectively control tumor onset and progression. In this review, we address important considerations and challenges regarding the development of cancer immunoprevention for non-viral cancers. We also discuss significant, innovative, and impactful preclinical and clinical immunoprevention studies in various cancers. This includes neoantigen discovery, the use and optimization of immunomodulating agents either alone or in combination with vaccines, and strategies for optimizing vaccines. We conclude by discussing prospects for immunoprevention research and potential opportunities to advance the field in the future.

Discovery and validation of frameshift-derived neopeptides in Lynch syndrome: paving the way for novel cancer prevention strategies

BACKGROUND

Lynch syndrome (LS), caused by germline pathogenic variants in the mismatch repair genes, leads to high rates of frameshift-derived neopeptide (FSDN) expression due to microsatellite instability (MSI). While colorectal cancer (CRC) prevention is effective, most LS-related tumors lack such strategies. Cancer vaccines targeting FSDNs offer a promising approach for immune interception in LS. This study aimed to identify and validate LS-related FSDNs to develop vaccines for cancer prevention.

METHODS

We identified LS-related coding MS mutations and predicted FSDN with high coverage on common Human Leukocyte Antigen (HLA)-I and II alleles. We validated FSDN-associated mutations in colorectal adenomas (CrAD), endometrial cancers (EC), and CRC samples from patients with LS, non-LS tumors, and cell lines. Immunogenicity was assessed through interferon (IFN)-γ enzyme-linked immunospot and flow cytometry analysis of tissue-infiltrating lymphocytes (TILs) from LS carriers.

RESULTS

We prioritized 53 HLA-I and 45 HLA-II FSDNs in MSI tumors using in silico predictions. Validation revealed 86.7% of FSDN-associated mutations present in LS-CRC samples, with a median of 7.67 (6.5-9) mutations in CrADs and 6.02 (2-10) in CRCs. Sequencing of CrAD and EC samples showed 95% and 77.5% of predicted FSDN-associated mutations, respectively. MSI cancer cell lines transcribed 69.8% of FSDNs. Immunogenicity assays showed that 71% of potential FSDNs elicited IFN-γ responses, with a median of 7.37 (1-10.75) HLA-I and 6 (2-5.75) HLA-II FSDNs per patient. After prioritizing 24 FSDN, in a cohort of 19 LS-derived samples (4 CrAD and 15 normal mucosa), 52% (10/19) demonstrated T-cell reactivity to an HLA-I neoantigen pool. CD8+CD137+ activation markers increased significantly (p=0.037) over time and peptide-specific cells were detected by pentamer staining.

CONCLUSIONS

Our predicted FSDN set has optimal coverage among LS carriers and can induce IFN-γ inflammatory responses in LS-derived TILs, offering an opportunity for vaccine development.

Advancements of nanoscale drug formulations for combination treatment of colorectal cancer

Combination chemotherapy is widely utilized in treating colorectal cancer (CRC), particularly for patients who are ineligible for surgery or those with metastatic CRC (mCRC). While this therapeutic method has demonstrated efficacy in managing CRC and mCRC, its broader clinical application is limited due to the unique physical properties, mechanisms of action, and pharmacokinetics of different chemotherapeutic drugs. Consequently, achieving satisfactory treatment outcomes proves to be challenging. Nanotechnology has given rise to innovative drug systems that are precise, controllable, and highly efficient in drug delivery. These nanoscale drug delivery systems can integrate the advantageous aspects of various therapeutic modalities, including chemotherapy, gene therapy, and immunotherapy. This review aims to explain the application of nano-drug delivery system in the treatment of colorectal cancer. Through its unique physical/chemical properties and biological functions, it can solve the limitations of traditional therapy and achieve more accurate, efficient and safe treatment. The advantages/disadvantages, physical and chemical characteristics of various drug delivery systems are described in detail, and suggestions on selecting reasonable NDDSs according to different drug combination methods are given to achieve the best therapeutic effect. This review paper presents an exhaustive summary of the diverse range of drugs utilized in chemotherapy, in addition to outlining strategies for effectively integrating chemotherapy with other treatment modalities. Furthermore, it delves into the principle of selecting carriers for various drug combinations.

Regulatory T cells in solid tumor immunotherapy: effect, mechanism and clinical application

The tumor-immune response is mobilized to suppress tumorigenesis, while the immune microenvironment and lymph node microenvironment are formed gradually during tumor progression. In fact, tumor surface antigens are not easily recognized by antigen-presenting cells. So it is hard for the immune system to kill the newly formed tumor cells effectively. In a normal immune environment, immune function is always suppressed to maintain the stability of the body, and regulatory T cells play an important role in maintaining immune suppression. However, during tumorigenesis, the suppression of regulatory T cell immune functions is more likely to contribute to tumor cell proliferation and migration leading directly to tumor progression. Therefore, focusing on the role of regulatory T cells in tumor immunity could improve tumor immunotherapy outcomes in the clinic. Regulatory T cells are more mature in hematologic system tumors than in solid tumors. However, there are continuing efforts to apply regulatory T cells for immunotherapy in solid tumors. This review describes the role of regulatory T cells in solid tumor immunotherapy from the perspective of prognosis, immune microenvironment remodeling, and current clinical applications. This summary could help us better understand the mechanisms of regulatory T cells in solid tumor immunotherapy and further expand their clinical application.

A frameshift-generated cancer neoepitope that controls tumor burden in prophylaxis as well as therapy

Insertion or deletion of one or two base pairs within a coding region causes a frameshift, which has the potential to generate neoepitopes (InDel-generated neoepitopes) that lack a self-counterpart and are entirely novel. Despite the obvious appeal of InDel-generated neoepitopes, and the demonstration of such candidate neoepitopes that can elicit a CD8 T-cell response, no InDel-generated neoepitopes that actually control tumors in vivo have been reported thus far. Here, in a mouse colon carcinoma line, we identify 11 InDels, only one of which generates a neoepitope that elicits tumor control in vivo in models of prophylaxis as well as therapy. Although this neoepitope has no self-counterpart, it has a low affinity (IC50 33,937.60 nM) for its MHC I allele. Despite its low affinity for MHC I, this neoepitope elicits antitumor activity in vivo through CD8 T cells. Furthermore, CD8 T cells elicited by this InDel-generated neoepitope, like the neoepitopes created by point mutations, show notably less exhaustion than classical immunogenic epitopes. Ironically, this InDel-generated neoepitope follows the same rules as noted for most of the tumor control-mediating neoepitopes generated by point mutations that have a poor affinity for MHC I alleles.

SITC strategic vision: prevention, premalignant immunity, host and environmental factors

Cancer immunotherapy has improved the survival of a subset of patients by harnessing the power of the immune system to find and destroy malignant cells. The immune system also protects the host by destroying developing premalignant and malignant tumors. Advancing our knowledge of premalignant immunity and immune changes seen in lesions that develop into invasive cancer versus those that regress offers an exciting opportunity to leverage the immune system for immune prevention and immune interception of premalignancy. Understanding the immune environment of premalignant lesions and how chronic inflammation plays a central role in the evolution of premalignancy is essential for developing effective immunoprevention and immune interceptions. Factors such as host genomics and environmental factors that affect premalignant immunity and the outcome of advanced cancers are equally important in determining the response to immunotherapy. The broad use of antibiotics and factors such as obesity can disrupt a healthy gut microbiome and drive chronic inflammation that suppresses preventive immunity or the antitumor immune response required for successful immunotherapy in advanced cancers. Modifiable lifestyle factors such as diet, obesity, smoking, and stress should be considered in designing immune prevention and interception studies, as well as for patients who receive immunotherapy for advanced cancer treatment. Other factors, such as the overall immune health of patients and existing comorbidities, affect both premalignant immunity and response to immunotherapy and, therefore, should be considered in managing patients with or without cancer. The Society for Immunotherapy of Cancer previously developed an overarching manuscript regarding the challenges and opportunities that exist in cancer immunotherapy, and this manuscript serves as an in-depth follow-up regarding the topics of premalignant immunity, immune interception, and immunoprevention, and the impact of the host on responding to immunotherapy.

Lower Degree of Microsatellite Instability in Colorectal Carcinomas From MSH6-Associated Lynch Syndrome Patients

Numerous observational and molecular studies focusing on Lynch syndrome (LS) have revealed significant variation in the phenotype and molecular characteristics among carriers of pathogenic variants in mismatch repair genes (path_MMR). Recently, we demonstrated that colorectal carcinomas in path_MSH6 carriers exhibit fewer insertion/deletion mutations compared with cumulative colorectal cancers (CRCs) from other MMR groups, raising the question of whether MSH6-mutated CRCs might display a relatively lower degree of microsatellite instability (MSI). Mutations at 20 coding microsatellites (cMS) were analyzed in 39 MSH6-, 18 MLH1-, 16 MSH2-, and 22 PMS2-mutated CRCs and 35 sporadic MSI CRCs, and mutation frequencies and mutant allele ratios were compared among the different MMR-deficient groups. Considering factors such as HLA-A∗02:01 type, B2M status, and the anticipated immunogenicity of frameshift peptides derived from cMS mutations, the identified cMS mutation profiles of MSH6-mutated CRCs were further investigated to assess their potential impact on immunotherapeutic strategies. MSH6-mutated CRCs exhibited lower mutation frequencies and mutant allele ratios across most cMS. Variation in cMS mutation patterns was observed both between different tumor regions and between tumor tissue and adjacent adenomatous tissue. The cMS mutations in MSH6-mutated CRCs demonstrated inverse correlations with the predicted immunogenicity of the resulting frameshift peptides, which may suggest a negative selection of cell clones bearing highly immunogenic frameshift peptides. Overall, MSH6-mutated CRCs display a relatively lower degree of MSI and represent a biologically distinct subgroup of LS-associated CRCs. This lower MSI level may implicate an altered immune response compared with other MSI CRCs, which could have theoretical implications for the success of immunotherapy in MSH6-mutated CRCs. Future studies should carefully evaluate this possibility. If confirmed, these results would reinforce the notion of classifying LS as distinct syndromes associated with specific MMR genes.

Neoantigen Vaccines in Cancer Prevention

Recent advances in cancer immunotherapy have established neoantigen-based vaccines as a promising approach to cancer prevention. Unlike tumor-associated antigens, neoantigens originate exclusively from somatic mutations, thus enabling tumor-specific targeting without harm to normal tissues. This distinctive feature promotes robust immune responses while reducing the risk of autoimmune side effects. Developing standardized "off-the-shelf" vaccines targeting shared neoantigens offers a scalable strategy for cancer prevention, particularly benefitting genetically predisposed high-risk populations. These vaccines can be administered to high-risk individuals before malignant transformation to potentially intercept cancer development through early immune activation. Advances in next-generation sequencing and computational biology have increased the accuracy of neoantigen prediction, while advances in vaccine delivery platforms have boosted vaccine efficacy. The integration of neoantigen-based vaccines with immune checkpoint inhibitors, immune stimulants, and classic chemopreventive agents has a synergistic potential to improve cellular immunity. This review examines biological mechanisms, clinical development, and future directions of neoantigen-based vaccines in cancer prevention, emphasizing their clinical potential to revolutionize risk-reduction strategies.

Tumour mutational burden using a targeted panel approach for comprehensive tumour profiling focusing on colorectal cancer

There is an increasing recognition that comprehensive tumour profiling (CTP) represents an important adjunct to the diagnosis of malignancy providing not only an assessment of how many mutations there are in any given tumour which reflects the probability of immune checkpoint inhibitor success, but also which mutations are associated with targeted therapies, a signature that reflects environmental insult and potentially the identification of cancers of unknown origin.This short review describes an approach to assaying tumour mutational burden (TMB), what the difficulties are in the assessment of the TMB and what it can be applied to in regards to improving patient outcomes. A final section of the review delves into some examples of colorectal cancer studies that identify findings that suggest there remains much to learn about tumour development.

Inhibition of histone methyltransferase EZH2 for immune interception of colorectal cancer in Lynch syndrome

Colorectal precancers in Lynch syndrome (LS) exhibit a distinct immune profile, presenting unique opportunities for developing immune-interception strategies to prevent carcinogenesis. Epigenetic modulation by EZH2 of immune-related genes is implicated in the carcinogenesis of different cancer types, including colorectal cancer. This study utilizes a mouse model of LS and ex vivo colonic organoids to assess the effects of the EZH2 inhibitor GSK503 on immune regulatory pathways, tumorigenesis, and epigenetic reprogramming. Our findings revealed that GSK503 significantly increased CD4+ and CD8+ T cells in both splenocytes and colonic mucosa of treated mice compared with controls. Additionally, a preventive dose of GSK503 over 9 weeks notably reduced adenoma multiplicity, demonstrating its efficacy as a preventive modality. Single-cell RNA-Seq and molecular analyses showed activation of immune and apoptotic markers, along with a reduction in H3K27 methylation levels in colonic crypts. ChIP sequencing further revealed decreased levels of H3K27me3 and H3K4me1, while levels of the active enhancer marks H3K4me3 and H3K27Ac increased in treated mice. Collectively, these findings indicate that EZH2 inhibition enhances immune responses through epigenetic reprogramming in the genome of LS mice, establishing a promising framework for the clinical development of EZH2 inhibitors as a cancer prevention strategy for LS carriers.

Single-cell spatial immune profiling for precision immunotherapy in Lynch syndrome

Lynch syndrome (LS) is the most common hereditary colorectal cancer (CRC) predisposition syndrome, characterized by a high mutational burden and microsatellite instability-high (MSI-H) tumors. Immunology of LS-associated CRC (LS-CRC) is unique, with significant implications for treatment. Despite well-established knowledge of LS immunology, immunotherapy dose and treatment response can vary significantly based on local tumor immunity and specific germline pathogenic variant of LS genes. This variability necessitates tailored surveillance strategies and new personalised immunotherapy approaches for LS patients. LS-CRC often benefits from immunotherapy due to the distinct tumor microenvironment (TME) and the variety of tumor infiltrating lymphocytes (TILs). This perspective discusses a novel approach of analysing spatial TILs at a single-cell level using tumor whole slide images (WSIs) that accounts for the distinct TME of LS-CRC. By emphasizing the necessity of personalized medicine in hereditary cancer syndromes, the future research and clinical practices that enhance patient outcomes through precision oncology is inspired.

Cancer vaccines: Target antigens, vaccine platforms and preclinical models

This review provides a comprehensive overview of the evolving landscape of cancer vaccines, highlighting their potential to revolutionize tumor prevention. Building on the success of vaccines against virus-related cancers, such as HPV- and HBV-associated cervical and liver cancers, the current challenge is to extend these achievements to the prevention of non-viral tumors and the treatment of preneoplastic or early neoplastic lesions. This review analyzes the critical aspects of preventive anti-cancer vaccination, focusing on the choice of target antigens, the development of effective vaccine platforms and technologies, and the use of various model systems for preclinical testing, from laboratory rodents to companion animals.

Vaccines for cancer prevention: exploring opportunities and navigating challenges

Improved understanding of cancer immunology has gradually brought increasing attention towards cancer-preventive vaccines as an important tool in the fight against cancer. The aim of this approach is to reduce cancer occurrence by inducing a specific immune response targeting tumours at an early stage before they can fully develop. The great advantage of preventive cancer vaccines lies in the potential to harness a less-compromised immune system in vaccine recipients before their immune responses become affected by the advanced status of the disease itself or by aggressive treatments such as chemotherapy. Successful implementation of immunoprevention against oncogenic viruses such as hepatitis B and papillomavirus has led to a dramatic decrease in virally induced cancers. Extending this approach to other cancers holds great promise but remains a major challenge. Here, we provide a comprehensive review of preclinical evidence supporting this approach, encouraging results from pioneering clinical studies as well as a discussion on the key aspects and open questions to address in order to design potent prophylactic cancer vaccines in the near future.

Factors influencing the colorectal surveillance adherence in Lynch Syndrome: A retrospective monocentric study

BACKGROUND

Lynch syndrome (LS), an autosomal dominant disorder resulting from germline pathogenic variants in DNA mismatch repair genes, poses an elevated risk of developing different types of cancer, particularly colorectal and endometrial. Early identification of LS individuals is vital for implementing preventive measures. This study aims to assess the adherence rate of LS individuals to colorectal surveillance and identify influencing factors.

METHODS

Data from the Hereditary Digestive Tumors Registry at Fondazione IRCCS Istituto Nazionale dei Tumori of Milan from 1995 to 2018 were analyzed. The study included 397 LS patients, as categorized based on adherence to surveillance. Statistical analyses, including multivariable logistic regression, were employed to identify factors influencing adherence.

RESULTS

Out of 397 LS patients, 305 (76.8%) completed surveillance, and 92 (23.2%) were lost during surveillance. Fifty-two patients developed colorectal cancer during the surveillance: 34 among patients who completed the surveillance and 18 among those who did not (p<0.036). Factors positively influencing adherence included genetic counseling and higher education, while the distance from the referral center had a negative impact. The survival rate was 83.5% at 240-months.

CONCLUSIONS

This study emphasizes the importance of adhering to a regular colorectal surveillance program for LS individuals. Genetic counseling and higher education emerged as a crucial factor positively affecting adherence. The negative impact was observed for geographical distance from the referral center.

Report of the sixth meeting of the European Consortium 'Care for CMMRD' (C4CMMRD), Paris, France, November 16th 2022

Biallelic germline pathogenic variants in one of the four mismatch repair genes (MSH2, MSH6, MLH1 and PMS2) cause a very rare, highly penetrant, childhood-onset cancer syndrome, called constitutional mismatch repair deficiency (CMMRD). The European consortium "Care for CMMRD" (C4CMMRD) was founded in Paris in 2013 to facilitate international collaboration and improve our knowledge of this rare cancer predisposition syndrome. Following initial publications on diagnostic criteria and surveillance guidelines for CMMRD, several partners collaborating within the C4CMMRD consortium have worked on and published numerous CMMRD-related clinical and biological projects. Since its formation, the C4CMMRD consortium held meetings every 1-2 years (except in 2020 and 2021 due to the Covid 19 pandemic). The sixth C4CMMRD meeting was held in Paris in November 2022, and brought together 42 participants from nine countries involved in various fields of CMMRD healthcare. The aim was to update members on the latest results and developments from ongoing research, and to discuss and initiate new study proposals. As previously done for the fifth meeting of the C4CMMRD group, this report summarizes data presented at this meeting.

Personalized Immunotherapy Achieves Complete Response in Metastatic Adenoid Cystic Carcinoma Despite Lack of Conventional Biomarkers

There is currently no effective treatment strategy for recurrent/metastatic adenoid cystic carcinoma (R/M ACC). Furthermore, recent single-agent and combination immunotherapy trials have failed in unselected ACC cohorts, unlike non-ACC salivary gland cancers. Genomic profiling revealed no actionable targets but NOTCH1 and KDM6A frameshift and CTCF splice site mutations (no MYB/L fusion) with a low tumor mutational burden (TMB), microsatellite stable (MSS) and negative programmed death ligand 1 (PD-L1) were observed. We recommended an anti-programmed cell death protein 1 (anti-PD-1) plus anti-Cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4) combination based on TMB 2-fold greater-than-median TMB in ACC, tumor harboring multiple immunogenic frameshift or splice site mutations, and PD-L1 negativity. Accordingly, we achieved a complete response in a radiotherapy (RT) and chemotherapy (CT)-refractory patient with locally recurrent lacrimal gland (LG) ACC and lung metastasis following personalized immunotherapy in combination with integrative therapeutics. Therefore, it is crucial to assess not only conventional immune biomarkers but also patient-specific parameters, especially in "immune-cold" cancer types.

Potent therapeutic strategy in gastric cancer with microsatellite instability-high and/or deficient mismatch repair

Gastric cancer (GC) is a common malignancy that presents challenges in patient care worldwide. The mismatch repair (MMR) system is a highly conserved DNA repair mechanism that protects genome integrity during replication. Deficient MMR (dMMR) results in an increased accumulation of genetic errors in microsatellite sequences, leading to the development of a microsatellite instability-high (MSI-H) phenotype. Most MSI-H/dMMR GCs arise sporadically, mainly due to MutL homolog 1 (MLH1) epigenetic silencing. Unlike microsatellite-stable (MSS)/proficient MMR (pMMR) GCs, MSI-H/dMMR GCs are relatively rare and represent a distinct subtype with genomic instability, a high somatic mutational burden, favorable immunogenicity, different responses to treatment, and prognosis. dMMR/MSI-H status is a robust predictive biomarker for treatment with immune checkpoint inhibitors (ICIs) due to high neoantigen load, prominent tumor-infiltrating lymphocytes, and programmed cell death ligand 1 (PD-L1) overexpression. However, a subset of MSI-H/dMMR GC patients does not benefit from immunotherapy, highlighting the need for further research into predictive biomarkers and resistance mechanisms. This review provides a comprehensive overview of the clinical, molecular, immunogenic, and therapeutic aspects of MSI-H/dMMR GC, with a focus on the impact of ICIs in immunotherapy and their potential as neoadjuvant therapies. Understanding the complexity and diversity of the molecular and immunological profiles of MSI-H/dMMR GC will drive the development of more effective therapeutic strategies and molecular targets for future precision medicine.

Immunoprevention Strategies for Colorectal Cancer in Lynch Syndrome Carriers

ABSTRACT

The immune revolution that swept the field of oncology in the mid-2010s with the advent of checkpoint inhibitors has led to a paradigm shift in approaches toward adapting new cancer prevention modalities. Cancer vaccines have emerged from this era with astounding potential as a durable intervention to prevent cancers especially for patients with hereditary susceptibilities such as Lynch syndrome carriers. This review covers new insights in the immunoprevention landscape for patients living with Lynch syndrome including highlights ranging from clinical trials exploring the use of chemoprevention agents to boost immune cellularity to investigative studies using novel vaccine approaches to induce long-term antitumor immunity.

[Lynch syndrome]

Patients with Lynch syndrome, one of the most common hereditary tumor predisposition syndromes, harbor an increased risk for a broad spectrum of especially gastrointestinal and gynecological tumors. Causative for the syndrome are variants in DNA mismatch repair genes, which are passed on to the offspring at a 50% chance (autosomal dominant inheritance). The tumor tissue of these patients usually shows microsatellite instability, which is of increasing relevance regarding prognosis and therapeutic decisions. The detection of a causative genetic variant in a patient enables predictive testing of family members to provide relief to noncarriers and provide carriers with intensified risk-adapted surveillance. In addition, chemoprevention with aspirin (acetylsalicylic acid) has been proven useful for chemoprevention in studies. Therefore, the diagnosis of Lynch syndrome is important for patients and their relatives.

Death receptors 4/5 mediate tumour sensitivity to natural killer cell-mediated cytotoxicity in mismatch repair deficient colorectal cancer

BACKGROUND

Identifying the target of natural killer (NK) cells in colorectal cancer (CRC) is critical for optimising the clinical use of NK cell-mediated immunotherapy. Mismatch repair deficiency (dMMR) is associated with high immune cell infiltration and MHC Class I defects. Whether dMMR CRC responses to NK cell therapy remains unclear.

METHODS

MLH1, DR4, and DR5 knockout cell lines were established using CRISPR-Cas9 system. NK92-MI or NK cell isolated from BABL/C mice were used as effector cells against tumour cells. Inflammatory cytokines secretion by CRC cells was assessed via cytokine analysis. NK-cell-deficient/proficient animal models were used to validate the NK cell sensitivity.

RESULTS

We observed that dMMR CRC cells were more sensitive to NK cell-mediated cytotoxicity than were mismatch-repair-proficient (pMMR) CRC cells. In dMMR CRC, Death receptor (DR)4/5 was upregulated and mediated sensitivity to NK cell-mediated cytotoxicity. DR4/5-mediated secretion of interleukin -12 sustained NK cell viability in dMMR CRC. NK cell depletion induced dMMR CRC tumour growth, and NK cell transfer inhibited lung metastasis of dMMR CRC with DR4/5 expression in vivo. TP53 upregulated DR4/DR5 expression in dMMR CRC.

CONCLUSIONS

dMMR associated with increased sensitivity to NK cell-mediated cytotoxicity in CRC. DR4/DR5 sensitise dMMR CRC to NK cell-mediated cytotoxicity.

Frameshift mutations in peripheral blood as a biomarker for surveillance of Lynch syndrome

BACKGROUND

Lynch syndrome is a hereditary cancer predisposition syndrome caused by germline mutations in DNA mismatch repair genes, which lead to high microsatellite instability and frameshift mutations at coding mononucleotide repeats in the genome. Recurrent frameshift mutations in these regions are thought to play a central role in the increased risk of various cancers, but no biomarkers are currently available for the surveillance of high microsatellite instability-associated cancers.

METHODS

A frameshift mutation-based biomarker panel was developed and validated by targeted next-generation sequencing of supernatant DNA from cultured high microsatellite instability colorectal cancer cells. This panel supported selection of 122 frameshift mutation targets as potential biomarkers. This biomarker panel was then tested using matched tumor, adjacent normal tissue, and buffy coat samples (53 samples) and blood-derived cell-free DNA (cfDNA) (38 samples) obtained from 45 high microsatellite instability and mismatch repair-deficient patients. We also sequenced cfDNA from 84 healthy participants to assess background noise.

RESULTS

Recurrent frameshift mutations at coding mononucleotide repeats were detectable not only in tumors but also in cfDNA from high microsatellite instability and mismatch repair-deficient patients, including a Lynch syndrome carrier, with a varying range of target detection (up to 85.2%), whereas they were virtually undetectable in healthy participants. Receiver operating characteristic curve analysis showed high sensitivity and specificity (area under the curve = 0.94) of the investigated panel.

CONCLUSIONS

We demonstrated that frameshift mutations can be detected in cfDNA from high microsatellite instability and mismatch repair-deficient patients and asymptomatic carriers. The 122-target frameshift mutation panel described here has promise as a tool for improved surveillance of high microsatellite instability and mismatch repair-deficient patients, with the potential to reduce the frequency of invasive screening methods for this high-cancer-risk cohort.

Novel Cancer Prevention Strategies in Individuals With Hereditary Cancer Syndromes: Focus on BRCA1, BRCA2, and Lynch Syndrome

Germline pathogenic variants (PVs) in the BRCA1 and BRCA2 genes confer elevated risks of breast, ovarian, and other cancers. Lynch syndrome (LS) is associated with increased risks of multiple cancer types including colorectal and uterine cancers. Current cancer risk mitigation strategies have focused on pharmacologic risk reduction, enhanced surveillance, and preventive surgeries. While these approaches can be effective, they stand to be improved on because of either limited efficacy or undesirable impact on quality of life. The current review summarizes ongoing investigational efforts in cancer risk prevention strategies for patients with germline PVs in BRCA1, BRCA2, or LS-associated genes. These efforts span radiation, surgery, and pharmacology including vaccine strategies. Understanding the molecular events involved in the premalignant to malignant transformation in high-risk individuals may ultimately contribute significantly to novel prevention strategies.

Precision immuno-oncology approach for four malignant tumors in siblings with constitutional mismatch repair deficiency syndrome

Constitutional mismatch repair deficiency (CMMRD) is a rare syndrome characterized by an increased incidence of cancer. It is caused by biallelic germline mutations in one of the four mismatch repair genes (MMR) genes: MLH1, MSH2, MSH6, or PMS2. Accurate diagnosis accompanied by a proper molecular genetic examination plays a crucial role in cancer management and also has implications for other family members. In this report, we share the impact of the diagnosis and challenges during the clinical management of two brothers with CMMRD from a non-consanguineous family harbouring compound heterozygous variants in the PMS2 gene. Both brothers presented with different phenotypic manifestations and cancer spectrum. Treatment involving immune checkpoint inhibitors significantly contributed to prolonged survival in both patients affected by lethal gliomas. The uniform hypermutation also allowed immune-directed treatment using nivolumab for the B-cell lymphoma, thereby limiting the intensive chemotherapy exposure in this young patient who remains at risk for subsequent malignancies.

Chemoprevention in Inherited Colorectal Cancer Syndromes

Cancer prevention in hereditary gastrointestinal predisposition syndromes relies primarily on intensive screening (e.g., colonoscopy) or prophylactic surgery (e.g., colectomy). The use of chemopreventive agents as an adjunct to these measures has long been studied both in the general population and in hereditary cancer patients, in whom the risk of malignancy, and therefore the potential risk reduction, is considerably greater. However, to date only few compounds have been found to be effective, safe, and tolerable for widespread use. Furthermore, many of the studies involving these rare syndromes suffer from small sample sizes, heterogeneous patient cohorts, short follow-up duration, and lack of standardized endpoints, creating challenges to draw generalizable conclusion regarding efficacy. The following review summarizes the current data on various chemopreventive compounds used in Lynch syndrome and familial adenomatous polyposis in addition to several agents that are currently being investigated.

Emerge of colorectal cancer in Lynch syndrome despite colonoscopy surveillance: A challenge of hide and seek

Even with colonoscopy surveillance, Lynch syndromes (LS) carriers still develop colorectal cancer (CRC). The cumulative incidence of CRCs under colonoscopy surveillance varies depending on the affected mismatch repair (MMR) gene. However, the precise mechanisms driving these epidemiological patterns remain incompletely understood. In recent years, several potential mechanisms explaining the occurrence of CRCs during colonoscopy surveillance have been proposed in individuals with and without LS. These encompass biological factors like concealed/accelerated carcinogenesis through a bypassed adenoma stage and accelerated progression from adenomas. Alongside these, various colonoscopy-related factors may contribute to formation of CRCs under colonoscopy surveillance, like missed yet detectable (pre)cancerous lesions, detected yet incompletely removed (pre)cancerous lesions, and colonoscopy-induced carcinogenesis due to tumor cell reimplantation. In this comprehensive literature update, we reviewed these potential factors and evaluated their relevance to each MMR group in an attempt to raise further awareness and stimulate research regarding this conflicting phenomenon.

Current Trends in Vaccine Development for Hereditary Colorectal Cancer Syndromes

The coming of age for cancer treatment has experienced exponential growth in the last decade with the addition of immunotherapy as the fourth pillar to the fundamentals of cancer treatment-chemotherapy, surgery, and radiation-taking oncology to an astounding new frontier. In this time, rapid developments in computational biology coupled with immunology have led to the exploration of priming the host immune system through vaccination to prevent and treat certain subsets of cancer such as melanoma and hereditary colorectal cancer. By targeting the immune system through tumor-specific antigens-namely, neoantigens (neoAgs)-the future of cancer prevention may lie within arm's reach by employing neoAg vaccines as an immune-preventive modality for hereditary cancer syndromes like Lynch syndrome. In this review, we discuss the history, current trends, utilization, and future direction of neoAg-based vaccines in the setting of hereditary colorectal cancer.

Tumor Antigens beyond the Human Exome

With the advent of immunotherapeutics, a new era in the combat against cancer has begun. Particularly promising are neo-epitope-targeted therapies as the expression of neo-antigens is tumor-specific. In turn, this allows the selective targeting and killing of cancer cells whilst healthy cells remain largely unaffected. So far, many advances have been made in the development of treatment options which are tailored to the individual neo-epitope repertoire. The next big step is the achievement of efficacious "off-the-shelf" immunotherapies. For this, shared neo-epitopes propose an optimal target. Given the tremendous potential, a thorough understanding of the underlying mechanisms which lead to the formation of neo-antigens is of fundamental importance. Here, we review the various processes which result in the formation of neo-epitopes. Broadly, the origin of neo-epitopes can be categorized into three groups: canonical, noncanonical, and viral neo-epitopes. For the canonical neo-antigens that arise in direct consequence of somatic mutations, we summarize past and recent findings. Beyond that, our main focus is put on the discussion of noncanonical and viral neo-epitopes as we believe that targeting those provides an encouraging perspective to shape the future of cancer immunotherapeutics.

Immunotherapy of MSI Cancer: Facts and Hopes

Microsatellite instability (MSI) is a tumor molecular phenotype that evolves from loss of function in the mismatch repair (MMR) proteins through deleterious germline mutations, epigenetic inactivation, or somatic biallelic mutations. This phenotype is characterized by genomic hyper-mutability, increased neoantigen expression, and a favorable, immune-rich tumor microenvironment. These features confer a greater likelihood of response to treatment with the class of agents known as immune checkpoint inhibitors (ICI) and, potentially, other immune-based therapeutics. MSI as a predictive biomarker for response to treatment with ICIs ultimately led to the first tissue-agnostic approval of pembrolizumab for advanced, previously treated MSI or deficient MMR (dMMR) tumors. Nevertheless, response to ICIs in dMMR/MSI tumors is not universal. Identifying predictors of response and elucidating mechanisms of immune escape will be crucial to continued successful treatment of this subset. In this review, we aim to describe the pathogenesis and key immunologic features of dMMR/MSI tumors, provide a brief overview of the currently approved treatments, and discuss promising novel immune-based therapeutics currently under investigation.

NCI Resources for Cancer Immunoprevention Research

Cancer prevention and early detection, the first two of the eight primary goals of the National Cancer Plan released in April 2023, are at the forefront of the nation's strategic efforts to reduce cancer incidence and mortality. The Division of Cancer Prevention (DCP) of the NCI is the federal government's principal component devoted to promoting and supporting innovative cancer prevention research. Recent advances in tumor immunology, cancer immunotherapy, and vaccinology strongly suggest that the host immune system can be effectively harnessed to elicit protective immunity against the development of cancer, that is, cancer immunoprevention. Cancer immunoprevention may be most effective if the intervention is given before or early in the carcinogenic process while the immune system remains relatively uncompromised. DCP has increased the emphasis on immunoprevention research in recent years and continues to expand program resources and interagency collaborations designed to facilitate research in the immunoprevention field. These resources support a wide array of basic, translational, and clinical research activities, including discovery, development, and validation of biomarkers for cancer risk assessment and early detection (Early Detection Research Network), elucidation of biological and pathophysiological mechanistic determinants of precancer growth and its control (Translational and Basic Science Research in Early Lesions), spatiotemporal multiomics characterization of precancerous lesions (Human Tumor Atlas Network/Pre-Cancer Atlas), discovery of immunoprevention pathways and immune targets (Cancer Immunoprevention Network), and preclinical and clinical development of novel agents for immunoprevention and interception (Cancer Prevention-Interception Targeted Agent Discovery Program, PREVENT Cancer Preclinical Drug Development Program, and Cancer Prevention Clinical Trials Network).

The future of cancer vaccines against colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) is the second most lethal malignancy worldwide. Immune checkpoint inhibitors (ICIs) benefit only 15% of patients with mismatch repair-deficient/microsatellite instability (dMMR/MSI) CRC. The majority of patients are not suitable due to insufficient immune infiltration. Cancer vaccines are a potential approach for inducing tumor-specific immunity within the solid tumor microenvironment.

AREA COVERED

In this review, we have provided an overview of the current progress in CRC vaccines over the past three years and briefly depict promising directions for further exploration.

EXPERT OPINION

Cancer vaccines are certainly a promising field for the antitumor treatment against CRC. Compared to monotherapy, cancer vaccines are more appropriate as adjuvants to standard treatment, especially in combination with ICI blockade, for microsatellite stable patients. Improved vaccine construction requires neoantigens with sufficient immunogenicity, satisfactory HLA-binding affinity, and an ideal delivery platform with perfect lymph node retention and minimal off-target effects. Prophylactic vaccines that potentially prevent CRC carcinogenesis are also worth investigating. The exploration of appropriate biomarkers for cancer vaccines may benefit prognostic prediction analysis and therapeutic response prediction in patients with CRC. Although many challenges remain, CRC vaccines represent an exciting area of research that may become an effective addition to current guidelines.

A Thermosensitive Bi-Adjuvant Hydrogel Triggers Epitope Spreading to Promote the Anti-Tumor Efficacy of Frameshift Neoantigens

Tumor-specific frameshift mutations encoding peptides (FSPs) are highly immunogenic neoantigens for personalized cancer immunotherapy, while their clinical efficacy is limited by immunosuppressive tumor microenvironment (TME) and self-tolerance. Here, a thermosensitive hydrogel (FSP-RZ-BPH) delivering dual adjuvants R848 (TLR7/8 agonist) + Zn2+ (cGAS-STING agonist) is designed to promote the efficacy of FSPs on murine forestomach cancer (MFC). After peritumoral injection, FSP-RZ-BPH behaves as pH-responsive sustained drug release at sites near the tumor to effectively transform the immunosuppressive TME into an inflammatory type. FSP-RZ-BPH orchestrates innate and adaptive immunity to activate dendritic cells in tumor-draining lymph nodes and increase the number of FSPs-reactive effector memory T cells (TEM) in tumor by 2.9 folds. More importantly, these TEM also exhibit memory responses to nonvaccinated neoantigens on MFC. This epitope spreading effect contributes to reduce self-tolerance to maintain long-lasting anti-tumor immunity. In MFC suppressive model, FSP-RZ-BPH achieves 84.8% tumor inhibition rate and prolongs the survival of tumor-bearing mice with 57.1% complete response rate. As a preventive tumor vaccine, FSP-RZ-BPH can also significantly delay tumor growth. Overall, the work identifies frameshift MFC neoantigens for the first time and demonstrates the thermosensitive bi-adjuvant hydrogel as an effective strategy to boost bystander anti-tumor responses of frameshift neoantigens.

Advances and challenges in cancer immunoprevention and immune interception

Invasive cancers typically evade immune surveillance through profound local and systemic immunosuppression, preventing their elimination or control. Targeting immune interventions to prevent or intercept premalignant lesions, before significant immune dysregulation has occurred, may be a more successful strategy. The field of cancer immune interception and prevention is nascent, and the scientific community has been slow to embrace this potentially most rational approach to reducing the global burden of cancer. This may change due to recent promising advances in cancer immunoprevention including the use of vaccines for the prevention of viral cancers, the use of cancer-associated antigen vaccines in the setting of precancers, and the development of cancer-preventative vaccines for high-risk individuals who are healthy but carry cancer-associated heritable genetic mutations. Furthermore, there is increasing recognition of the importance of cancer prevention and interception by national cancer organizations. The National Cancer Institute (NCI) recently released the National Cancer Plan, which includes cancer prevention among the top priorities of the institute. The NCI's Division of Cancer Prevention has been introducing new funding opportunities for scientists with an interest in the field of cancer prevention: The Cancer Prevention-Interception Targeted Agent Discovery Program and The Cancer Immunoprevention Network. Moreover, the Human Tumor Atlas Network is spearheading the development of a precancer atlas to better understand the biology of pre-invasive changes, including the tissue microenvironment and the underlying genetics that drive carcinogenesis. These data will inform the development of novel immunoprevention/immuno-interception strategies. International cancer foundations have also started recognizing immunoprevention and immune interception with the American Association for Cancer Research, Cancer Research UK and the Society for Immunotherapy of Cancer each implementing programming focused on this area. This review will present recent advances, opportunities, and challenges in the emerging field of cancer immune prevention and immune interception.

Lynch Syndrome: From Multidisciplinary Management to Precision Prevention

BACKGROUND AND AIMS

Lynch syndrome (LS) is currently one of the most prevalent hereditary cancer conditions, accounting for 3% of all colorectal cancers and for up to 15% of those with DNA mismatch repair (MMR) deficiency, and it was one of the first historically identified. The understanding of the molecular carcinogenesis of LS tumors has progressed significantly in recent years. We aim to review the most recent advances in LS research and explore genotype-based approaches in surveillance, personalized cancer prevention, and treatment strategies.

METHODS

PubMed was searched to identify relevant studies, conducted up to December 2023, investigating molecular carcinogenesis in LS, surveillance strategies, cancer prevention, and treatment in LS tumors.

RESULTS

Multigene panel sequencing is becoming the benchmark in the diagnosis of LS, allowing for the detection of a pathogenic constitutional variant in one of the MMR genes. Emerging data from randomized controlled trials suggest possible preventive roles of resistant starch and/or aspirin in LS. Vaccination with immunogenic frameshift peptides appears to be a promising approach for both the treatment and prevention of LS-associated cancers, as evidenced by pre-clinical and preliminary phase 1/2a studies.

CONCLUSIONS

Although robust diagnostic algorithms, including prompt testing of tumor tissue for MMR defects and referral for genetic counselling, currently exist for suspected LS in CRC patients, the indications for LS screening in cancer-free individuals still need to be refined and standardized. Investigation into additional genetic and non-genetic factors that may explain residual rates of interval cancers, even in properly screened populations, would allow for more tailored preventive strategies.

Genetic predisposition to gastrointestinal polyposis: syndromes, tumour features, genetic testing, and clinical management

Gastrointestinal tract polyposis is characterised by the presence of multiple polyps, particularly in the colorectum, and encompasses both cancer predisposition genetic syndromes and non-syndromic clinical manifestations. The sources of the heterogeneity observed in polyposis syndromes relate to genetic cause, mode of inheritance, polyp burden and histological type, and spectrum and frequency of extracolonic manifestations. These features determine the clinical management of carriers, including strategies for cancer prevention and early detection, and oncological treatments. Despite substantial progress in identifying the genetic causes of polyposis, a large proportion of cases remain genetically unexplained. Although some of these cases might be due to lifestyle, environmental factors, or cancer treatments, it is likely that additional polyposis predisposition genes will be identified. This Review provides an overview of the known syndromes and genes, genetic testing, and clinical management of patients with polyposis, and recent advances and challenges in the field of gastrointestinal polyposis.

The Cancer Moonshot Immuno-Oncology Translational Network at 5: accelerating cancer immunotherapies

The Immuno-Oncology Translational Network (IOTN) was established in 2018 as part of the Cancer Moonshot. In 2022, President Joe Biden set new goals to reduce the cancer death rate by half within 25 years and improve the lives of people with cancer and cancer survivors. The IOTN is focused on accelerating translation of cancer immunology research, from bench to bedside, and improving immunotherapy outcomes across a wide array of cancers in the adult population. The unique structure and team science approach of the IOTN is designed to accelerate discovery and evaluation of novel immune-based therapeutic and prevention strategies. In this article, we describe IOTN progress to date, including new initiatives and the development of a robust set of resources to advance cancer immunology research. We summarize new insights by IOTN researchers, some of which are ripe for translation for several types of cancers. Looking to the future, we identify barriers to the translation of immuno-oncology concepts into clinical trials and key areas for action and improvements that are suitable for high-yield investments. Based on these experiences, we recommend novel National Institutes of Health funding mechanisms and development of new resources to address these barriers.

SUMOylation and DeSUMOylation: Prospective therapeutic targets in cancer

The SUMO family is a type of ubiquitin-like protein modification molecule. Its protein modification mechanism is similar to that of ubiquitination: both involve modifier-activating enzyme E1, conjugating enzyme E2 and substrate-specific ligase E3. However, polyubiquitination can lead to the degradation of substrate proteins, while poly-SUMOylation only leads to the degradation of substrate proteins through the proteasome pathway after being recognized by ubiquitin as a signal factor. There are currently five reported subtypes in the SUMO family, namely SUMO1-5. As a reversible dynamic modification, intracellular sentrin/SUMO-specific proteases (SENPs) mainly regulate the reverse reaction pathway of SUMOylation. The SUMOylation modification system affects the localization, activation and turnover of proteins in cells and participates in regulating most nuclear and extranuclear molecular reactions. Abnormal expression of proteins related to the SUMOylation pathway is commonly observed in tumors, indicating that this pathway is closely related to tumor occurrence, metastasis and invasion. This review mainly discusses the composition of members in the protein family related to SUMOylation pathways, mutual connections between SUMOylation and other post-translational modifications on proteins as well as therapeutic drugs developed based on these pathways.

Dominantly inherited micro-satellite instable cancer - the four Lynch syndromes - an EHTG, PLSD position statement

The recognition of dominantly inherited micro-satellite instable (MSI) cancers caused by pathogenic variants in one of the four mismatch repair (MMR) genes MSH2, MLH1, MSH6 and PMS2 has modified our understanding of carcinogenesis. Inherited loss of function variants in each of these MMR genes cause four dominantly inherited cancer syndromes with different penetrance and expressivities: the four Lynch syndromes. No person has an "average sex "or a pathogenic variant in an "average Lynch syndrome gene" and results that are not stratified by gene and sex will be valid for no one. Carcinogenesis may be a linear process from increased cellular division to localized cancer to metastasis. In addition, in the Lynch syndromes (LS) we now recognize a dynamic balance between two stochastic processes: MSI producing abnormal cells, and the host's adaptive immune system's ability to remove them. The latter may explain why colonoscopy surveillance does not reduce the incidence of colorectal cancer in LS, while it may improve the prognosis. Most early onset colon, endometrial and ovarian cancers in LS are now cured and most cancer related deaths are after subsequent cancers in other organs. Aspirin reduces the incidence of colorectal and other cancers in LS. Immunotherapy increases the host immune system's capability to destroy MSI cancers. Colonoscopy surveillance, aspirin prevention and immunotherapy represent major steps forward in personalized precision medicine to prevent and cure inherited MSI cancer.

Mismatch repair deficiency is not sufficient to elicit tumor immunogenicity

DNA mismatch repair deficiency (MMRd) is associated with a high tumor mutational burden (TMB) and sensitivity to immune checkpoint blockade (ICB) therapy. Nevertheless, most MMRd tumors do not durably respond to ICB and critical questions remain about immunosurveillance and TMB in these tumors. In the present study, we developed autochthonous mouse models of MMRd lung and colon cancer. Surprisingly, these models did not display increased T cell infiltration or ICB response, which we showed to be the result of substantial intratumor heterogeneity of mutations. Furthermore, we found that immunosurveillance shapes the clonal architecture but not the overall burden of neoantigens, and T cell responses against subclonal neoantigens are blunted. Finally, we showed that clonal, but not subclonal, neoantigen burden predicts ICB response in clinical trials of MMRd gastric and colorectal cancer. These results provide important context for understanding immune evasion in cancers with a high TMB and have major implications for therapies aimed at increasing TMB.

Advances in vaccine development for cancer prevention and treatment in Lynch Syndrome

Lynch Syndrome (LS) is one of the most common hereditary cancer syndromes, and is caused by mutations in one of the four DNA mismatch repair (MMR) genes, namely MLH1, MSH2, MSH6 and PMS2. Tumors developed by LS carriers display high levels of microsatellite instability, which leads to the accumulation of large numbers of mutations, among which frameshift insertion/deletions (indels) within microsatellite (MS) loci are the most common. As a result, MMR-deficient (MMRd) cells generate increased rates of tumor-specific neoantigens (neoAgs) that can be recognized by the immune system to activate cancer cell killing. In this context, LS is an ideal disease to leverage immune-interception strategies. Therefore, the identification of these neoAgs is an ongoing effort for the development of LS cancer preventive vaccines. In this review, we summarize the computational methods used for in silico neoAg prediction, including their challenges, and the experimental techniques used for in vitro validation of their immunogenicity. In addition, we outline results from past and on-going vaccine clinical trials and highlight avenues for improvement and future directions.

Advancing translational research for colorectal immuno-oncology

Colorectal cancer (CRC) is a common and deadly disease. Unfortunately, immune checkpoint inhibitors (ICIs) fail to elicit effective anti-tumour responses in the vast majority of CRC patients. Patients that are most likely to respond are those with DNA mismatch repair deficient (dMMR) and microsatellite instability (MSI) disease. However, reliable predictors of ICI response are lacking, even within the dMMR/MSI subtype. This, together with identification of novel mechanisms to increase response rates and prevent resistance, are ongoing and vitally important unmet needs. To address the current challenges with translation of early research findings into effective therapeutic strategies, this review summarises the present state of preclinical testing used to inform the development of immuno-regulatory treatment strategies for CRC. The shortfalls and advantages of commonly utilised mouse models of CRC, including chemically induced, transplant and transgenic approaches are highlighted. Appropriate use of existing models, incorporation of patient-derived data and development of cutting-edge models that recapitulate important features of human disease will be key to accelerating clinically relevant research in this area.

Organoids and metastatic orthotopic mouse model for mismatch repair-deficient colorectal cancer

Background

Genome integrity is essential for the survival of an organism. DNA mismatch repair (MMR) genes (e.g., MLH1, MSH2, MSH6, and PMS2) play a critical role in the DNA damage response pathway for genome integrity maintenance. Germline mutations of MMR genes can lead to Lynch syndrome or constitutional mismatch repair deficiency syndrome, resulting in an increased lifetime risk of developing cancer characterized by high microsatellite instability (MSI-H) and high mutation burden. Although immunotherapy has been approved for MMR-deficient (MMRd) cancer patients, the overall response rate needs to be improved and other management options are needed.

Methods

To better understand the biology of MMRd cancers, elucidate the resistance mechanisms to immune modulation, and develop vaccines and therapeutic testing platforms for this high-risk population, we generated organoids and an orthotopic mouse model from intestine tumors developed in a Msh2-deficient mouse model, and followed with a detailed characterization.

Results

The organoids were shown to be of epithelial origin with stem cell features, to have a high frameshift mutation frequency with MSI-H and chromosome instability, and intra- and inter-tumor heterogeneity. An orthotopic model using intra-cecal implantation of tumor fragments derived from organoids showed progressive tumor growth, resulting in the development of adenocarcinomas mixed with mucinous features and distant metastasis in liver and lymph node.

Conclusions

The established organoids with characteristics of MSI-H cancers can be used to study MMRd cancer biology. The orthotopic model, with its distant metastasis and expressing frameshift peptides, is suitable for evaluating the efficacy of neoantigen-based vaccines or anticancer drugs in combination with other therapies.

TIME for Bugs: The Immune Microenvironment and Microbes in Precancer

Major advances in our understanding of the tumor immune microenvironment (TIME) in established cancer have been made, including the influence of host-intrinsic (host genomics) and -extrinsic factors (such as diet and the microbiome) on treatment response. Nonetheless, the immune and microbiome milieu across the spectrum of precancerous tissue and early neoplasia is a growing area of interest. There are emerging data describing the contribution of the immune microenvironment and microbiota on benign and premalignant tissues, with opportunities to target these factors in cancer prevention and interception. Throughout this review, we provide rationale for not only the critical need to further elucidate the premalignant immune microenvironment, but also for the utility of pharmacologic and lifestyle interventions to alter the immune microenvironment of early lesions to reverse carcinogenesis. Novel research methodologies, such as implementing spatial transcriptomics and proteomics, in combination with innovative sampling methods will advance precision targeting of the premalignant immune microenvironment. Additional studies defining the continuum of immune and microbiome evolution, which emerges in parallel with tumor development, will provide novel opportunities for cancer interception at the earliest steps in carcinogenesis.

The screening, identification, design and clinical application of tumor-specific neoantigens for TCR-T cells

Recent advances in neoantigen research have accelerated the development of tumor immunotherapies, including adoptive cell therapies (ACTs), cancer vaccines and antibody-based therapies, particularly for solid tumors. With the development of next-generation sequencing and bioinformatics technology, the rapid identification and prediction of tumor-specific antigens (TSAs) has become possible. Compared with tumor-associated antigens (TAAs), highly immunogenic TSAs provide new targets for personalized tumor immunotherapy and can be used as prospective indicators for predicting tumor patient survival, prognosis, and immune checkpoint blockade response. Here, the identification and characterization of neoantigens and the clinical application of neoantigen-based TCR-T immunotherapy strategies are summarized, and the current status, inherent challenges, and clinical translational potential of these strategies are discussed.

Vaccination and Microbiota Manipulation Approaches for Colon Cancer Prevention in Rodent Models

Colorectal cancer represents the third most common cancer type worldwide and is a leading cause of cancer-related mortality in the United States and Western countries. Rodent models have been invaluable to study the etiology of colorectal cancer and to test novel chemoprevention avenues. In the past, the laboratory mouse has become one of the best preclinical models for these studies due to the availability of genetic information for commonly used mouse strains with well-established and precise gene targeting and transgenic techniques. Well-established chemical mutagenesis technologies are also being used to develop mouse and rat models of colorectal cancer for prevention and treatment studies. In addition, xenotransplantation of cancer cell lines and patient-derived xenografts has been useful for preclinical prevention studies and drug development. This review focuses on the recent use of rodent models to evaluate the utility of novel strategies in the prevention of colon cancers including immune prevention approaches and the manipulation of the intestinal microbiota.

Biology of Precancers and Opportunities for Cancer Interception: Lesson from Colorectal Cancer Susceptibility Syndromes

Hereditary gastrointestinal cancer is associated with molecular and neoplastic precursors which have revealed much about sporadic carcinogenesis. Therefore, an appreciation of constitutional and somatic events linked to these syndromes have provided a useful model for the development of risk models and preventative strategies. In this review, we focus of two of the best characterized syndromes, Lynch syndrome (LS) and familial adenomatous polyposis (FAP). Our understanding of the neoplasia-immune interaction in LS has contributed to the development of immune mediated therapies including cancer preventing vaccines and immunotherapy for cancer precursors. Chemoprevention in LS with aspirin and nonsteroidal anti-inflammatory drugs has also translated into clinical cancer, however the efficacy of such agents in FAP remains elusive when cancer is applied as an endpoint in trials rather than the use of 'indirect' endpoints such as polyp burden, and requires further elucidation of biological mechanisms in FAP. Finally, we review controversies in gastrointestinal surveillance for LS and FAP, including limitations and opportunities of upper and lower gastrointestinal endoscopy in the prevention and early detection of cancer.

Immune escape and resistance to immunotherapy in mismatch repair deficient tumors

Up to 30% of colorectal, endometrial and gastric cancers have a deficiency in mismatch repair (MMR) protein expression due to either germline or epigenetic inactivation. Patients with Lynch Syndrome who inherit an inactive MMR allele have an up to 80% risk for developing a mismatch repair deficient (MMRd) cancer. Due to an inability to repair DNA, MMRd tumors present with genomic instability in microsatellite regions (MS). Tumors with high MS instability (MSI-H) are characterized by an increased frequency of insertion/deletions (indels) that can encode novel neoantigens if they occur in coding regions. The high tumor antigen burden for MMRd cancers is accompanied by an inflamed tumor microenvironment (TME) that contributes to the clinical effectiveness of anti-PD-1 therapy in this patient population. However, between 40 and 70% of MMRd cancer patients do not respond to treatment with PD-1 blockade, suggesting that tumor-intrinsic and -extrinsic resistance mechanisms may affect the success of checkpoint blockade. Immune evasion mechanisms that occur during early tumorigenesis and persist through cancer development may provide a window into resistance pathways that limit the effectiveness of anti-PD-1 therapy. Here, we review the mechanisms of immune escape in MMRd tumors during development and checkpoint blockade treatment, including T cell dysregulation and myeloid cell-mediated immunosuppression in the TME. Finally, we discuss the development of new therapeutic approaches to tackle resistance in MMRd tumors, including cancer vaccines, therapies targeting immunosuppressive myeloid programs, and immune checkpoint combination strategies.

CLDN5 identified as a biomarker for metastasis and immune infiltration in gastric cancer via pan-cancer analysis

BACKGROUND

CLDN5 protein is essential for the formation of tight junctions in epithelial cells, and has been associated with epithelial-mesenchymal transition. Research has indicated that CLDN5 is associated with tumor metastasis, the tumor microenvironment, and immunotherapy in multiple types of cancer. Also, no comprehensive evaluation of the expression of CLDN5 and immunotherapy signatures through a pan-cancer analysis or immunoassay has been performed.

METHODS

We explored CLDN5's differential expression, survival analysis and clinicopathological staging through the TCGA database, and then corroborated the expression of CLDN5 by utilizing the GEO (Gene expression omnibus) database. To analyze CLDN5 KEGG, GO, and Hallmark mutations, as well as TIMER for immune infiltration, GSEA was utilized with ROC curve, mutation, and other factors such as survival, pathological stage, TME, MSI, TMB, immune cell infiltration, and DNA methylation. Immunohistochemistry was used to assess CLDN5 staining in gastric cancer tissues and paracancerous tissues. Visualization was done with R version 4.2.0 (http://www.rproject.org/).

RESULTS

According to TCGA database, CLDN5 expression levels differed significantly between cancer and normal tissues, and the GEO database (GSE49051 and GSE 64951) and tissue microarrays confirmed this result. Infiltrating cluster of differentiation 8+ (CD8+) T cells, CD4+ cells, neutrophils, dendritic cells, and macrophages revealed a correlation with CLDN5 expression. DNA methylation, TMB, and MSI are related to CLDN5 expression. Based on the ROC curve analysis, CLDN5 demonstrates outstanding diagnostic effectiveness for gastric cancer and is comparable to CA-199.

CONCLUSIONS

The findings suggest that CLDN5 is implicated in the oncogenesis of diverse cancer types, underscoring its potential significance in cancer biology. Notably, CLDN5 could have implications in immune filtration and immune checkpoint inhibitor therapies, however, further research is needed to confirm this.

Is HLA type a possible cancer risk modifier in Lynch syndrome?

Lynch syndrome (LS) is the most common inherited cancer syndrome. It is inherited via a monoallelic germline variant in one of the DNA mismatch repair (MMR) genes. LS carriers have a broad 30% to 80% risk of developing various malignancies, and more precise, individual risk estimations would be of high clinical value, allowing tailored cancer prevention and surveillance. Due to MMR deficiency, LS cancers are characterized by the accumulation of frameshift mutations leading to highly immunogenic frameshift peptides (FSPs). Thus, immune surveillance is proposed to inhibit the outgrowth of MMR-deficient cell clones. Recent studies have shown that immunoediting during the evolution of MMR-deficient cancers leads to a counter-selection of highly immunogenic antigens. The immunogenicity of FSPs is dependent on the antigen presentation. One crucial factor determining antigen presentation is the HLA genotype. Hence, a LS carrier's HLA genotype plays an important role in the presentation of FSP antigens to the immune system, and may influence the likelihood of progression from precancerous lesions to cancer. To address the challenge of clarifying this possibility including diverse populations with different HLA types, we have established the INDICATE initiative (Individual cancer risk by HLA type, http://indicate-lynch.org/), an international network aiming at a systematic evaluation of the HLA genotype as a possible cancer risk modifier in LS. Here we summarize the current knowledge on the role of HLA type in cancer risk and outline future research directions to delineate possible association in the scenario of LS with genetically defined risk population and highly immunogenic tumors.