Lynch Syndrome Colorectal Cancer Research Articles

Adherence to national Lynch syndrome testing guidelines for colorectal cancer in an Aotearoa New Zealand hospital-based population.

Lynch syndrome (LS) is estimated to affect 1-3.9% of patients with colorectal cancer (CRC). Testing for LS is important in determining management and establishing surveillance for "Lynch families". Previous studies have identified poor rates of testing for LS in CRC patients. This study aimed to describe adherence to guidelines for testing of newly diagnosed CRC for LS. A single institution cohort study of patients over 18 years with colorectal adenocarcinoma from 2018-2022 in Te Tai Tokerau, Aotearoa New Zealand was conducted. Rates of baseline immunohistochemistry (IHC) testing for mismatch repair (MMR) deficiency, further testing for MLH1-deficient cases and rates of germline mutational analysis were audited to determine adherence to national guidelines. The rate of LS in newly diagnosed CRC was estimated. Six hundred and sixty patients were eligible for universal testing for LS, of which 84% (n=553) completed initial IHC testing. MMR deficiency was reported in 20% (n=114) cases. Eighty-nine percent (n=101) was attributable to MLH1 deficiency, of which 99% (n=100) were appropriately tested for BRAF-V600E mutation. Sixty-four percent (4/11) patients indicated for hypermethylation testing were appropriately tested. Seventeen patients had an indication for germline mutational analysis, of which only 29% (n=5) were tested. The estimated incidence of LS in newly diagnosed CRC was 0.7-3.8%. Compliance with initial IHC testing was good. However, there is a need to improve rates of confirmation genetic testing. The incidence of confirmed LS in this study is 0.7%, however this may be as high as 3.9%.

Fusobacterium species are distinctly associated with patients with Lynch syndrome colorectal cancer

Accumulating evidence demonstrates clear correlation between the gut microbiota and sporadic colorectal cancer (CRC). Despite this, there is limited understanding of the association between the gut microbiota and CRC in Lynch Syndrome (LS), a hereditary type of CRC. Here, we analyzed fecal shotgun metagenomic and targeted metabolomic of 71 Japanese LS subjects. A previously published Japanese sporadic CRC cohort, which includes non-LS controls, was utilized as a non-LS cohort (n= 437). LS subjects exhibited reduced microbial diversity and low-Faecalibacterium enterotypes compared to non-LS. Patients with LS-CRC had higher levels of Fusobacterium nucleatum and fap2. Differential fecal metabolites and functional genes suggest heightened degradation of lysine and arginine in LS-CRC. A comparison between LS and non-LS subjects prior to adenoma formation revealed distinct fecal metabolites of LS subjects. These findings suggest that the gut microbiota plays a more responsive role in CRC tumorigenesis in patients with LS than those without LS.

Abstract 7552: Inhibition of histone methyltransferase EZH2 for immune-interception of colorectal cancer in Lynch syndrome

Abstract Introduction: Colorectal pre-cancers in Lynch Syndrome (LS) display a distinct immune profile thus presenting a unique opportunity to develop novel immune-interception approaches to halt carcinogenesis. Epigenetic modulation by EZH2 of immune-related genes has been implicated in many cancers including colorectal but it has yet to be explored in LS carcinogenesis. The main objective of this study is to test the effect of EZH2 inhibition on immune cell profiling, colorectal carcinogenesis, gene expression, and histone methylation, using ex vivo organoids and a LS mouse model. Methods: A mouse model of LS colorectal carcinogenesis (Villin-Cre;Msh2fl/fl;TgfβRII-KI; herein referred to as VCMsh2THu) and ex vivo colonic organoids were utilized to assess the effects of the EZH2 inhibitor GSK503. Mice were treated for 9-weeks with GSK503 with downstream studies exploring polyp multiplicity, changes to the immune landscape, and epigenetic analyses to derive mechanistic insights into EZH2 regulation in LS. Results: GSK503 significantly altered transcriptomic changes in VCMsh2THu organoids with tissue-specific tropism for dysplastic organoids as compared to organoids prepared from adjacent normal mucosa. GSK503 significantly increased CD4+and CD8+ T cells in splenocytes and colonic mucosa of treated mice compared to controls in vitro and in vivo. A preventive-dose (200μg/kg) of GSK503 for 9 weeks significantly reduced adenoma multiplicity in the large intestine of VCMsh2THu mice with significant changes in the immune landscape of treated mice compared to controls. The data suggests GSK503 significantly enriched both total and activated cytotoxic T-lymphocytes CD8+/CD137+), stromal macrophages (CD68+), and activated helper T-lymphocytes (CD4+/CD134+) in the large intestine of VCMsh2THu mice. Transcriptome and molecular analyses using IHC, Western blots, and computational tools showed activation of immune and apoptotic markers with concomitant reduction of H3K27 methylation levels in colonic crypts. ChIPseq analyses revealed decreased levels of H3K27me3 and H3K4me1 (enhancer), a slight increased levels of H3K27ac (enhancer) marks with no changes in levels of H3K4me3 in treated mice, indicating that EZH2 inhibition yields global reprograming of poised promoters and active enhancers in the LS mouse genome. Conclusions: Collectively, our findings reveal that GSK503 has a promising potential as an immuno-interception modality establishing the framework for launching phase I clinical trials with EZH2 inhibitors for LS carriers. Citation Format: Fahriye Duzagac, Charles M. Bowen, Laura Reyes-Uribe, Mahira Zaheer, Jacklyn Thompson, Nan Deng, Melissa Taggart, Abhinav Jain, Winfried Edelmann, Krishna M. Sinha, Eduardo Vilar. Inhibition of histone methyltransferase EZH2 for immune-interception of colorectal cancer in Lynch syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7552.

Clinicopathological features of post-colonoscopy colorectal cancer in patients with Japanese Lynch syndrome: A multicentric retrospective observational study.

79 Background: Due to the high incidence of heterochronic and concurrent colorectal cancer in Lynch syndrome (LS), colonoscopic surveillance is recommended in Japan every 1-2 years. Even with regular colonoscopic surveillance, post-colonoscopy colorectal cancer (PCCRC) often occurs in the intervals between surveillance, but there are currently no reports of the details of PCCRC in LS in Japan. Methods: Of 1756 colonoscopies performed between 2009 and 2018 in 316 patients with a diagnosis of LS confirmed by genetic testing who were enrolled in a nationwide, Japanese, multicentric study conducted by the Committee of Hereditary Colorectal Cancer of the Japanese Society for Cancer and Rectum, 1203 colonoscopies in 256 patients were assessed to determine the clinicopathological characteristics of PCCRC, after including cases of first-time surveillance, previously untreated lesions, and inadequate pretreatment. Then, the incidence of PCCRC was compared between patients with a median surveillance colonoscopy interval < 12 months (group A) and > 12 months (group B). Results: There were 49 cases of PCCRC with a total of 84 lesions. The number of lesions per tumor depth was 66, one, five, seven, four, and one for pTis, pT1, pT1a, pT1b, pT2, and pT3, respectively. Two (2.4%), 20 (23.8%), 21 (25%), four (4.8%), 18 (21.4%), and 19 (22.6%) lesions were localized in the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum, respectively. In pTis-pT1b, the macroscopic type was 0-IIa in 33 lesions (41.8%), 0-IIc in four lesions (5.1%), 0-IIa+IIc in five lesions (6.3%), 0-IIb in one lesion (1.3%), 0-Is in 15 lesions (19%), 0-Ip in one lesion (1.3%), 0-Isp in 16 lesions (20.3%), and unknown in four lesions. In pT1b-pT3, seven lesions (63.6%) were smaller than 20 mm. In terms of the median interval between surveillance colonoscopies, 130 patients had a median interval < 12 months (group A), and 126 patients had a median interval > 12 months (group B). In groups A and B, PCCRC, metachronous cases, simultaneous cases, and depths than pT1b were observed in 29 (22%) and 20 (16%) cases (p=0.21); 14 (11%) and two (1.6%) cases (p=0.006); six (4.6%) and one (0.8%) case (p=0.22), and six (4.6%) and four (3.2%) cases (p=1), respectively. Conclusions: In PCCRC in Lynch syndrome, invasive carcinomas < 2 cm should be noted. In addition, a surveillance interval of 12 months may be insufficient in patients with LS. Thus, further investigation is warranted.

Retrospective review of compliance with guideline-directed germline testing in microsatellite instability-high colorectal cancer treated at the Veterans Health Administration.

86 Background: Lynch syndrome (LS) is an autosomal dominant inherited cancer syndrome that confers an increased risk of colorectal cancer (CRC). As clinical and history features under-recognize LS cases (3-5% of CRC), universal screening of CRCs for LS is recommended. Patients whose CRCs are mismatch repair protein deficient (dMMR) and/or microsatellite instability high (MSI-H) are recommended to have subsequent genetics evaluation to screen for germline mutations. Confirmed LS changes cancer surveillance recommendations for affected patients and their relatives. Within Veterans Health Administration (VHA), GT is ordered by genetic counselors at genomic medicine telehealth centers (GMTC), after initial consultation. We aim to quantify rates at which CRC patients treated at the VHA complete germline testing (GT) when indicated. Methods: The electronic health records (EHRs) of VHA patients with known dMMR/MSI-H CRC were reviewed. Cases were extracted from both Veterans Affairs (VA) Puget Sound and referral VA MSI testing laboratories. Surgical pathology reports and clinical documentation were reviewed in Joint Longitudinal Viewer (JLV) to determine if GT was indicated and reason for non-testing, if not performed. Patients with known LS prior to development of CRC were excluded, and patients with dMMR in MLH1 or MSI-H with concurrent BRAFV600 mutation and/or MLH1 hypermethylation were considered to have sporadic CRC. Results: Of 110 patients with abnormal tumor LS screening; 39 (36%) patients’ tumor tissue underwent IHC for dMMR, 16 (14%) underwent PCR for MSI, and 55 (50%) had both. 45 (41%) patients were classified as somatic MSI-H. 65 (59%) patients met criteria for referral for GMTC and GT. Of these 65, 49 ultimately did not undergo GT and 16 did, which confirmed 4 cases of LS and revealed 1 variant of uncertain significance in the MLH1 gene. Reasons for non-testing were: 7 (14%) declined all cancer testing and treatment after CRC diagnosis or were lost to follow-up/declined establishment of cancer care, 3 (6%) declined referral to GMTC, 14 (29%) accepted referral to GMTC but never had consultation, 7 (14%) accepted referral to GMTC but declined GT when offered, and 18 (37%) were never offered GMTC referral or GT. Conclusions: A majority of dMMR/MSI-H cases with an indication for GT were referred for genetic counseling, but only a small subset completed testing. This analysis identified multiple areas for improvement, including a lack of recognition by providers for the need for GT, and lack of completion of testing by patients at multiple levels. Further evaluation of VHA-specific barriers is needed to improve the quality of delivered care.

MTHFR C677T and A1298C polymorphism’s effect on risk of colorectal cancer in Lynch syndrome

Lynch syndrome (LS) is characterised by an increased risk of developing colorectal cancer (CRC) and other extracolonic epithelial cancers. It is caused by pathogenic germline variants in DNA mismatch repair (MMR) genes or the EPCAM gene, leading to a less functional DNA MMR system. Individuals diagnosed with LS (LS individuals) have a 10–80% lifetime risk of developing cancer. However, there is considerable variability in the age of cancer onset, which cannot be attributed to the specific MMR gene or variant alone. It is speculated that multiple genetic and environmental factors contribute to this variability, including two single nucleotide polymorphisms (SNPs) in the methylenetetrahydrofolate reductase (MTHFR) gene: C677T (rs1801133) and A1298C (rs1801131). By decreasing MTHFR activity, these SNPs theoretically reduce the silencing of DNA repair genes and increase the availability of nucleotides for DNA synthesis and repair, thereby protecting against early-onset cancer in LS. We investigated the effect of these SNPs on LS disease expression in 2,723 LS individuals from Australia, Poland, Germany, Norway and Spain. The association between age at cancer onset and SNP genotype (risk of cancer) was estimated using Cox regression adjusted for gender, country and affected MMR gene. For A1298C (rs1801131), both the AC and CC genotypes were significantly associated with a reduced risk of developing CRC compared to the AA genotype, but no association was seen for C677T (rs1801133). However, an aggregated effect of protective alleles was seen when combining the alleles from the two SNPs, especially for LS individuals carrying 1 and 2 alleles. For individuals with germline pathogenic variants in MLH1, the CC genotype of A1298C was estimated to reduce the risk of CRC significantly by 39% (HR = 0.61, 95% CI 0.42, 0.89, p = 0.011), while for individuals with pathogenic germline MSH2 variants, the AC genotype (compared to AA) was estimated to reduce the risk of CRC by 26% (HR = 0.66, 95% CI 0.53, 0.83, p = 0.01). In comparison, no association was observed for C677T (rs1801133). In conclusion, our study suggests that combining the MMR gene information with the MTHFR genotype, including the aggregated effect of protective alleles, could be useful in developing an algorithm that estimates the risk of CRC in LS individuals.

Efficacy of PD-1 inhibitors for colorectal cancer and polyps in Lynch syndrome patients

BackgroundProgrammed death-1 (PD-1) inhibitor is effective for colorectal cancer (CRC) with deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H). We aimed to explore its effects on CRCs and colonic polyps in Lynch syndrome (LS) patients. MethodsLS patients with CRC who had evaluable tumours and received at least 2 cycles of PD-1 inhibitors were retrospectively included. PD-1 inhibitors were given as a monotherapy or in combination with other therapies, including anticytotoxic T-lymphocyte-associated antigen-4 treatment, radiotherapy, chemotherapy, and targeted therapy. Correlations of treatment responses with clinicopathological characteristics and genomic profiles were analysed. ResultsA total of 75 LS patients were included, with a median age of 39 years. The median duration of follow-up was 27 months (range, 3–71). The objective response rate (ORR) was 70.7%, including 28.0% (n = 21) complete responses and 42.7% (n = 32) partial responses. Four of five cases of LS CRCs displaying proficient MMR (pMMR) or microsatellite stable (MSS) were not responsive. Mucinous/signet-ring cell differentiation was associated with a lower ORR (P = 0.013). The 3-year overall survival and progression-free survival were 91.2% and 82.2%, respectively. A polyp was detected in 26 patients during surveillance. Seven adenomas disappeared after treatment, and they were all larger than 7 mm. ConclusionPD-1 inhibitors are highly effective for dMMR and MSI-H LS CRCs, but not for pMMR or MSS LS CRCs or mucinous/signet-ring cell CRC. Large LS adenomas may also be eliminated by anti-PD-1 treatment. Data Availability StatementDue to the privacy of patients, the related data cannot be available for public access but can be obtained from Pei-Rong Ding (dingpr@sysucc.org.cn) upon reasonable request. The key raw data have been uploaded to the Research Data Deposit public platform (www.researchdata.org.cn).

Efficacy of PD-1 inhibitors for colorectal cancer and polyps in patients with Lynch syndrome.

e15521 Background: Programmed death-1 (PD-1) inhibitor is effective for colorectal cancer (CRC) with deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H). We aimed to explore its effects on CRCs and colonic polyps in Lynch syndrome (LS) patients. Methods: LS patients with CRC who had evaluable tumors and received ≥2 cycles of PD-1 inhibitors were included. PD-1 inhibitors were given as a monotherapy or in combination with other therapies including anti cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) treatment, radiotherapy, chemotherapy, and targeted therapy. Correlations of treatment responses with clinicopathological characteristics and genomic profiles were analyzed. Results: A total of 75 LS patients were included, with a median age of 39 years. The median duration of follow-up was 27 months (range, 3 to 71). The objective response rate (ORR) was 70.7%, including 28.0% (n = 21) complete responses (CRs) and 42.7% (n = 32) partial responses (PRs). Three cases of LS CRCs displaying pMMR/MSS or discordant MMR/MSI status were not responsive even with a high tumor mutation burden (TMB). Mucinous/signet-ring cell differentiation was associated with a lower ORR ( P= 0.013). The 3-year OS and PFS was 91.2% and 81.0%, respectively. Colorectal polyp/adenoma was detected in 26 patients during surveillance. Seven adenomas disappeared after treatment and their maximum diameters were all larger than 7mm. Conclusions: PD-1 inhibitors are highly effective for dMMR/MSI-H LS CRCs, but not for pMMR/MSS LS CRCs or those displaying discordant MMR/MSI status or mucinous/signet-ring cell CRC. Some of the large LS adenomas may also be sensitive to anti-PD-1 treatment.

Associating patient perceptions to poor uptake of aspirin (ASA) chemoprevention in a single-center cohort of patients with Lynch syndrome (LS).

e15662 Background: LS is among the most common hereditary cancer (CA) syndromes, underlying 3% cases of colorectal CA (CRC) and 8% of CRC < 50 yrs. Pts with LS have a very high lifetime risk of CRC, which has been shown to be decreased by intensive colonoscopy (COLO) surveillance. However, interval LS CRCs can still develop, and adjunctive therapies like ASA have been recognized for their chemoprev benefits, with 35% risk reduction associated with sustained ( > 2 yrs) use. Existing data are scarce on uptake of ASA chemoprev in LS pts, as well as pt-level factors that may impact uptake. Methods: PREVENTLynch recruited LS participants in the Fox Chase Cancer Center (FCCC) Risk Registry, who were invited to complete a one-time e-survey after providing informed consent (1/2020-6/2020; IRB 20-8014). Demographic/personal/familial CA history were collected. Inconvenience (INC), side effects (SEs), prevention reassurance (PR), and likelihood of recommending (LoR) available and emerging CA prevention modalities were measured on 9-point scales (low = 1 vs high = 9). Results: 116 LS pts completed the survey. Mean age was 53 yrs [range 23-76 ]. 24.7% (33/116) reported being on ASA, with 24.2% (8/33) taking it for an unrelated cardiac indication. 96.6% (112/116) had completed COLO, with 60.5% getting annual screening and 39.5% getting screening in 2-3 yrs. No significant difference was noted among ASA users and non-users based on age, race and underlying genetic LS subtype. A majority of pts (61.6%) were on ASA 81 mg/day, while 24.3% and 12% reported taking 325 and 650 mg/day, respectively. LS pts both taking and not taking ASA perceived it to be convenient (mean INC: 1.18 ASA users vs 2.11 non-users, p = 0.01). Concern for SEs was lower in ASA users than non-users (mean 1.09 vs 2.30, p = 0.003) while PR of the protective benefits was higher in the ASA users (mean PR 5.94 vs 3.23, p < 0.001). When comparing ASA to COLO, COLO was seen as more INC than ASA by both ASA users and non-users (mean COLO INC 3.0 and 3.1, p = 0.0001 and 0.017 compared to ASA INC, respectively). ASA users were more likely to recommend ASA to others (8.13 vs 4.09, p < 0.001). Conclusions: ASA uptake is low among LS pts. ASA is perceived as a favorable modality of chemoprev in only a fraction of LS pts, with perceived SEs and low PR as barriers to uptake. There is a critical need to address negative perceptions of chemoprev in LS patients as more options are developed. [Table: see text]

Contemporary surgical management of colorectal cancer in Lynch syndrome.

Lynch syndrome is the most common hereditary colorectal cancer syndrome. Although the current literature has been supportive of extended resections in certain Lynch syndrome patients with colon cancer. This article reviews the recent data on the topic and raises questions about the importance of homogenous high-quality prospective data to establish the accurate risk of cancer and future risk of metachronous cancer in the setting of all these risk reduction interventions.

Mismatch repair deficiency testing in Lynch syndrome-associated urothelial tumors.

Lynch syndrome-associated cancer develops due to germline pathogenic variants in one of the mismatch repair (MMR) genes, MLH1, MSH2, MSH6 or PMS2. Somatic second hits in tumors cause MMR deficiency, testing for which is used to screen for Lynch syndrome in colorectal cancer and to guide selection for immunotherapy. Both MMR protein immunohistochemistry and microsatellite instability (MSI) analysis can be used. However, concordance between methods can vary for different tumor types. Therefore, we aimed to compare methods of MMR deficiency testing in Lynch syndrome-associated urothelial cancers. Ninety-seven urothelial (61 upper tract and 28 bladder) tumors diagnosed from 1980 to 2017 in carriers of Lynch syndrome-associated pathogenic MMR variants and their first-degree relatives (FDR) were analyzed by MMR protein immunohistochemistry, the MSI Analysis System v1.2 (Promega), and an amplicon sequencing-based MSI assay. Two sets of MSI markers were used in sequencing-based MSI analysis: a panel of 24 and 54 markers developed for colorectal cancer and blood MSI analysis, respectively. Among the 97 urothelial tumors, 86 (88.7%) showed immunohistochemical MMR loss and 68 were successfully analyzed by the Promega MSI assay, of which 48 (70.6%) were MSI-high and 20 (29.4%) were MSI-low/microsatellite stable. Seventy-two samples had sufficient DNA for the sequencing-based MSI assay, of which 55 (76.4%) and 61 (84.7%) scored as MSI-high using the 24-marker and 54-marker panels, respectively. The concordance between the MSI assays and immunohistochemistry was 70.6% (p = 0.003), 87.5% (p = 0.039), and 90.3% (p = 1.00) for the Promega assay, the 24-marker assay, and the 54-marker assay, respectively. Of the 11 tumors with retained MMR protein expression, four were MSI-low/MSI-high or MSI-high by the Promega assay or one of the sequencing-based assays. Our results show that Lynch syndrome-associated urothelial cancers frequently had loss of MMR protein expression. The Promega MSI assay was significantly less sensitive, but the 54-marker sequencing-based MSI analysis showed no significant difference compared to immunohistochemistry. Data from this study alongside previous studies, suggest that universal MMR deficiency testing of newly diagnosed urothelial cancers, using immunohistochemistry and/or sequencing-based MSI analysis of sensitive markers, offer a potentially useful approach to identification of Lynch syndrome cases.

Identification and genetic counseling for a novel variant of MLH1 associated with lynch syndrome in colorectal cancer: a case report.

Identification and genetic counseling for a novel variant of MLH1 associated with lynch syndrome in colorectal cancer: a case report.

A comparative cost analysis of two screening strategies for colorectal cancer in Lynch Syndrome in a South African tertiary hospital.

Lynch Syndrome (LS) individuals have a 25-75% lifetime risk of developing colorectal cancer. Colonoscopy screening decreases this risk. This study compared the cost of Strategy 1: screening colonoscopy for 1st degree relatives of patients that met the Revised Bethesda Criteria (i.e., probands) to Strategy 2: screening colonoscopy for 1st degree relatives of probands with genetic mutations for Lynch Syndrome based in a resource-constrained health care system. A comparative, health care provider perspective, cost analysis was conducted at a tertiary hospital, using a micro-costing, ingredient approach. Forty probands that underwent genetic testing between November 01, 2014 and October 30, 2015 and their first-degree relatives were costed according to Strategy 1 and Strategy 2. Unit costs of colonoscopy and genetic testing were estimated and used to calculate and compare the total costs per strategy in South African rand (R) converted to UK pounds (£). Sensitivity analyses were performed on colonoscopy adherence, relatives' positivity, and variable discount rates. The cost for Strategy 1 amounted to £653 344/R6 161 035 compared to £49 327/R 465155 for Strategy 2 (Discount rate 3%; Adherence 75%; and Positivity rate of relatives 45%). Base case analysis indicated a difference of 92% less in the total cost for Strategy 2 compared to Strategy 1. Sensitivity analyses showed that the difference in cost between the two strategies was not sensitive to variations in adherence, positivity or discount rates. Colonoscopy screening for LS and at-risk family members was tenfold less costly when combined with genetic analysis. The logistics of rolling out this strategy nationally should be investigated.

Risk of cancer in individuals with Lynch-like syndrome and their families: a systematic review

BackgroundLynch-like syndrome (LLS) tumors have similar clinicopathological features to Lynch syndrome (LS) tumors but have no identifiable pathogenic germline mismatch repair gene variant. However, cancer risks in LLS patients and first-degree relatives (FDRs) are not well defined.MethodsTo clarify LLS-associated cancer risks, a systematic review of all studies examining all cancer risks in LLS was performed. Searching of Medline, Embase, Pubmed, Cochrane and CINAHL databases and reference/citation checking identified relevant studies published between January 1, 1980 and February 11, 2021. Joanna Briggs Institute Appraisal Tools assessed the risk of bias.ResultsSix studies (five cohort/one cross-sectional) were eligible for study inclusion. One study found no difference in colorectal cancer (CRC) incidence between LLS and LS patients or CRC risks at aged 70 years. Three studies found CRC incidence in LLS FDRs was higher than the general population but lower than LS FDRs. Two studies showed no difference in CRC diagnosis age between LLS patients and LS patients. Endometrial cancer risks in LLS patients were higher than the general population but lower than LS patients.ConclusionEvidence of elevated CRC risks in LLS patients and FDRs supports increased colonoscopy surveillance strategies for LLS patients and FDRs in line with current recommendations for LS. Due to heterogeneity amongst LLS populations, extended intervals between screening may be advised for low-risk families. Studies to resolve the molecular characterization and definition of LLS are needed to clarify cancer risks associated with LLS which in turn may individualize surveillance strategies for LLS patients and families.

Lynch syndrome pre-screening and comprehensive characterization in a multi-center large cohort of Chinese patients with colorectal cancer.

Objective:Lynch syndrome (LS) pre-screening methods remain under-investigated in colorectal cancers (CRCs) in Asia. Here, we aimed to systematically investigate LS pre-screening and comprehensively characterize LS CRCs.Methods:Microsatellite instability (MSI) and germline variants of DNA mismatch repair (MMR) genes were examined in 406 deficient MMR (dMMR) and 250 proficient MMR CRCs. The genetic differences between LS and sporadic CRCs were studied with whole exome sequencing analysis.Results:The incidence of dMMR in Chinese patients with CRCs was 13.8%. Consistency analysis between MMR immunohistochemistry (IHC) and MSI testing showed the kappa value was 0.758. With next-generation sequencing (NGS), germline variants were detected in 154 CRCs. Finally, 88 patients with CRC were identified as having LS by Sanger sequencing. Among them, we discovered 21 previously unreported pathogenic germline variants of MMR genes. Chinese patients with LS, compared with sporadic CRCs, tended to be early-onset, right-sided, early-stage and mucinous. Overall, the performance of MMR IHC and MSI testing for LS pre-screening was comparable: the area under the ROC curve for dMMR, MSI-H, and MSI-H/L was 0.725, 0.750, and 0.745, respectively. dMMR_MSI-H LS and sporadic CRCs showed substantial differences in somatic genetic characteristics, including different variant frequencies of APC, CREBBP, and KRAS, as well as different enriched pathways of VEGF, Notch, TGFβR, mTOR, ErbB, and Rac protein signal transduction.Conclusions:MMR IHC and MSI testing were effective methods for LS pre-screening. The revealed clinical and somatic genetic characteristics in LS CRCs may have the potential to improve the performance of LS pre-screening in combination with dMMR/MSI.

Risk of Metachronous Colorectal Cancer in Lynch Syndrome: Who Needs an Extended Resection?

Lynch syndrome (LS) is the most common genetic condition associated with early-onset colorectal cancer. It is inherited in an autosomal dominant fashion. The increased cancer risk is due to a germline mutation in one of the mismatch repair (MMR) genes (MLH1, MSH2, MSH6, and PMS2) or the EPCAM gene. This leads to a deficient DNA mismatch repair mechanism, resulting in the accumulation of nucleotide changes and microsatellite instability, providing phenotypical evidence that MMR is not functioning normally. LS is associated with a high risk of early-onset colorectal cancer and recurrence. Thus, when undergoing surgery for primary colorectal cancer, extended resection should be discussed with the patient. This review provides an overview of current surgical risk-reducing strategies in LS-associated colorectal cancer. Surgical treatment for LS carriers with colorectal cancer needs to be highly individualized, based on patient and disease characteristics. Strategies are presented to guide decision making in pathologic MMR gene mutation carriers undergoing surgery for colorectal cancer.

Abstract 721: Epigenetic intervention in the prevention of Lynch Syndrome Colorectal Cancer

Abstract Introduction: Lynch Syndrome (LS) is the most common cause of hereditary colorectal cancer (CRC) affecting >1 million Americans. LS is caused by germline mutations in one of four DNA mismatch repair (MMR) genes, generating several hundreds of mutations in microsatellite coding sequences. Although defects in the MMR machinery are the principal mechanism driving LS carcinogenesis, the role of the epigenome through histone and DNA methylation remains unexplored. Hypermethylation of MLH1 is detected in 15% of sporadic MMR-deficient CRC and also in LSCRC, indicating a pivotal role of DNA methylation in LSCRC. In this study, we investigated the landscape of DNA methylation and EZH2-mediated histone H3 lysine 27 methylation in LS tumor samples, and tested the preventive effects of GSK-503, on tumor formation using a novel LS mouse model. Methods: We profiled the somatic mutational, global DNA methylation landscape, and performed ChIP-seq in LS precancers and tumors. Patient-derived organoids (PDO) from colonic tissues treated with EZH2 and 5-AZA were used for gene expression analysis. LS mice (Villin-Cre;Msh2fl/fl;TgfβRII-KI) were treated for 9 weeks with EZH2 inhibitor GSK503 to assess the effect on polyp formation in vivo monitored through murine colonoscopy. Results: Our mutational profiling via whole-exome-seq and gene expression survey of 10 LSCRC and 33 pre-cancers showed accumulation of somatic mutations and aberrant expression patterns in key epigenetic regulators including EZH2 and DNMT3A, which suggests dysregulation of epigenetic control in LS. Global DNA methylation using RRBS in tumors of 3 LS patients showed that gene promoters were more hypermethylated when compared to matched normal samples. Immunohistochemistry data showed higher expression of EZH2 in tumors when compared to precancerous and normal colonic mucosa. ChIPseq analysis demonstrated high levels of H3K27me3 present in gene promoters of stem cell marker genes (WNT9A, LGR5, and ASCL2), and immune-related genes (CD4, CD8a, and HLA-E). Interestingly, 577 out of 2756 DNA hypermethylated genes from RRBS analysis displayed high levels of H3K27me3, thus indicating a central role of EZH2 in epigenetic programming of LS neoplasms. RNAseq data from PDOs treated with 5-AZA (DNMT inhibitor) and GSK503 (EZH2 inhibitor) showed that both epigenetic inhibitors led to the reactivation of silenced genes in colorectal carcinogenesis such as CDKN2A, RUNX3, IGFBP3, and immune genes, including CD40, CD4, SEMA3B, CXRC6/6, and ICAM1. Finally, a 9-week chemo-preventive treatment of a cohort of LS mice with GSK503 significantly decreased polyp formation when compared to control, and polyp reduction was associated with increased infiltration of cytotoxic CD8a+ Tcells and NK in the large intestine mucosa. Conclusions: These results demonstrate the chemopreventive potential of EZH2 inhibitors in prevention of LS-associated tumors through an immune modulation approach. Citation Format: Laura Reyes Uribe, Charles M Bowen, Kyera Evans, Hong Wu, Fahriye Duzagac, Krishna Sinha, Eduardo Vilar. Epigenetic intervention in the prevention of Lynch Syndrome Colorectal Cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 721.

Single institution assessment of compliance with guideline directed aspirin therapy in the prevention of colorectal cancer in Lynch syndrome.

e13637 Background: Patients with Lynch syndrome have up to 80% lifetime risk of developing colorectal cancer. Research shows chemoprevention with aspirin 600 mg for 25 months can reduce this risk for Lynch syndrome patients by 59%. In our study, we evaluated the compliance with aspirin therapy among Lynch patients at our institution. Methods: Our clinic identifies and follows all patients with a history of Lynch syndrome. Of our 125 patients, 62% were discovered after a family member was found to have a high-risk cancer, 29% were identified through MyCode, a DNA sequencing program which looks for gene mutations specific to Lynch. All patients in the clinic undergo discussion about starting aspirin therapy. Medication agreements and dosing are documented in the chart. Data was retrospectively reviewed to assess our patient compliance with recommendations. All data was based on subjective reports of compliance and reported doses. Results: 125 patients were included in the data analysis. Various risk factors were assessed including age, gender, history of cancer, and other comorbidities. Ages ranged from 20 to 78; 74% were female, 26% male. 90% of patients had a family cancer and of those, 47% had a personal history of cancer. Overall, 57% of patients agreed to take aspirin with doses ranging between 81 mg to 600 mg. 60.8% of patients took 81 mg of aspirin daily and 30.6% took 325 mg daily, citing concerns for bleeding and ulcer at higher doses. Only 8% of all patients agreeable to aspirin therapy took the recommended 600 mg dose. Of those who refused aspirin therapy, 5% reported allergy or prior intolerance, 13% had history of gastric ulcer or prior bleeding, 2% were taking medications which taken concomitantly with aspirin would increase risk of bleeding, and 80% provided no reason. Chi square test of independence was performed to examine the relationship between aspirin use and gender (χ² = 0.76, p = 0.38), age (χ² = 1.99, p = 0.37), and personal or family history of cancer (χ² = 9.89, p = .002). Results showed a patient with personal, or family history of cancer was more likely to take aspirin therapy, but there was no significant relationship among gender or age. Conclusions: Aspirin serves as an effective and affordable therapy for the prevention of colorectal cancer in patients with Lynch syndrome. Barriers to compliance should be identified and chemoprophylaxis should be initiated in all qualified patients. Future studies should be performed to establish more concrete recommendations about dosing and duration of aspirin therapy especially given the ease of access and cost effectiveness.[Table: see text]

Comparative molecular genomic analyses of a spontaneous rhesus macaque model of mismatch repair-deficient colorectal cancer.

Colorectal cancer (CRC) remains the third most common cancer in the US with 15% of cases displaying Microsatellite Instability (MSI) secondary to Lynch Syndrome (LS) or somatic hypermethylation of the MLH1 promoter. A cohort of rhesus macaques from our institution developed spontaneous mismatch repair deficient (MMRd) CRC with a notable fraction harboring a pathogenic germline mutation in MLH1 (c.1029C<G, p.Tyr343Ter). Our study aimed to provide a detailed molecular characterization of rhesus CRC for cross-comparison with human MMRd CRC. We performed PCR-based MSI testing (n = 41), transcriptomics analysis (n = 35), reduced-representation bisulfite sequencing (RRBS) (n = 28), and MLH1 DNA methylation (n = 10) using next-generation sequencing (NGS) of rhesus CRC. Systems biology tools were used to perform gene set enrichment analysis (GSEA) for pathway discovery, consensus molecular subtyping (CMS), and somatic mutation profiling. Overall, the majority of rhesus tumors displayed high levels of MSI (MSI-H) and differential gene expression profiles that were consistent with known deregulated pathways in human CRC. DNA methylation analysis exposed differentially methylated patterns among MSI-H, MSI-L (MSI-low)/MSS (MS-stable) and LS tumors with MLH1 predominantly inactivated among sporadic MSI-H CRCs. The findings from this study support the use of rhesus macaques as an alternative animal model to mice to study carcinogenesis, develop immunotherapies and vaccines, and implement chemoprevention approaches relevant to sporadic MSI-H and LS CRC in humans.

The Role of the Tumor Suppressor Gene Protein Tyrosine Phosphatase Gamma in Cancer.

Members of the Protein Tyrosine Phosphatase (PTPs) family are associated with growth regulation and cancer development. Acting as natural counterpart of tyrosine kinases (TKs), mainly involved in crucial signaling pathways such as regulation of cell cycle, proliferation, invasion and angiogenesis, they represent key parts of complex physiological homeostatic mechanisms. Protein tyrosine phosphatase gamma (PTPRG) is classified as a R5 of the receptor type (RPTPs) subfamily and is broadly expressed in various isoforms in different tissues. PTPRG is considered a tumor-suppressor gene (TSG) mapped on chromosome 3p14-21, a region frequently subject to loss of heterozygosity in various tumors. However, reported mechanisms of PTPRG downregulation include missense mutations, ncRNA gene regulation and epigenetic silencing by hypermethylation of CpG sites on promoter region causing loss of function of the gene product. Inactive forms or total loss of PTPRG protein have been described in sporadic and Lynch syndrome colorectal cancer, nasopharyngeal carcinoma, ovarian, breast, and lung cancers, gastric cancer or diseases affecting the hematopoietic compartment as Lymphoma and Leukemia. Noteworthy, in Central Nervous System (CNS) PTPRZ/PTPRG appears to be crucial in maintaining glioblastoma cell-related neuronal stemness, carving out a pathological functional role also in this tissue. In this review, we will summarize the current knowledge on the role of PTPRG in various human cancers.