Identification of DNA Repair-related Genes as Biomarkers Reflecting MSI, TMB, and TIL in Colorectal Cancer.

BACKGROUND/AIM: There are no established biomarkers for immune checkpoint inhibitors (ICI) in colorectal cancer (CRC) with microsatellite stability (MSS) or proficient mismatch repair (pMMR). Therefore, this study aimed to identify biomarkers for ICI benefit in patients with pMMR by analyzing the down-regulated DNA repair-related genes involved in highly immunogenic and immune responses, and comparing their expression levels and clinical features. MATERIALS AND METHODS: Mismatch repair (MMR), tumor-infiltrating lymphocytes (TIL), and tumor mutation burden (TMB) were evaluated in 13 CRC cases and mRNA expression levels of 95 DNA repair-related genes were measured. DNA repair-related genes with reduced mRNA expression in the high immunogenicity and high immune response groups were identified. Then, the mRNA expression levels of the identified DNA repair-related genes were measured in 135 patients with CRC. Hierarchical cluster analysis was performed using the mRNA expression levels to compare the clinicopathological characteristics of each cluster. RESULTS: ATR, LIG4, and RAD52 mRNA levels were significantly down-regulated in the high immunogenicity group. GADD45B, SMUG1, and XRCC6 mRNA levels were significantly down-regulated in the high immune response group. Cases in the cluster with reduced mRNA expression of the six genes were pMMR cases. CD8 mRNA expression level was higher in this cluster than in the other clusters. CONCLUSION: Decreased mRNA expression levels of ATR, LIG4, RAD52, GADD45B, SMUG1, and XRCC6 genes were associated with high cytotoxic T cell and TMB levels, suggesting that these genes could serve as biomarkers for ICI efficacy in pMMR cases.

[Clinicopathological features and prognosis of sporadic mismatch repair deficient colorectal cancer].

Objective: To investigate the clinicopathological characteristics and prognostic factors of sporadic mismatch repair deficient (dMMR) colorectal cancer. Methods: A total of 120 cases of sporadic dMMR colorectal cancer from July 2015 to April 2021 were retrospectively collected in Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. Patients with Lynch syndrome; synchronous multiple colorectal cancers; preoperative anti-tumor treatments such as chemotherapy and radiotherapy; and those with incomplete follow-up information were excluded based on family history and next-generation sequencing (NGS) test results. Immunohistochemical stains were used to detect the expression of mismatch repair proteins, methylation-specific PCR for methylation testing, and fluorescent PCR for BRAF V600E gene mutation detection. The clinical and pathological data, and gene mutation status were analyzed. Follow-up was done to assess survival and prognosis including progression-free survival and overall survival rate. Results: Sporadic dMMR colorectal cancer occurred more frequently in the right side of the colon, in females, and in the elderly. Morphologically, it was mostly moderately-differentiated, and most patients had low-grade tumor budding. In terms of immunohistochemical expression, MLH1 and PMS2 loss were dominant, and there were age and location-specificities in protein expression. MLH1 methylation was commonly detected in elderly female patients and rare in young male patients; while MLH1 and PMS2 deficiency, and BRAF V600E mutation occurred more often on the right side (P<0.05). The 3-year and 5-year progression-free survival rates were 90.7% and 88.7% respectively, and the 3-year and 5-year overall survival rates were 92.8% and 90.7% respectively. Tumor budding status was an independent risk factor affecting patient recurrence (hazard ratio=3.375, 95% confidence interval: 1.060-10.741, P=0.039), patients with low-grade tumor budding had better prognosis, and those with medium or high-grade tumor budding had poor prognosis. Conclusion: For dMMR colorectal cancer patients, tumor budding status is an independent risk factor for recurrence.

Analysis of clinical characteristics of mismatch repair status in colorectal cancer: a multicenter retrospective study.

BACKGROUND: Microsatellite instability (MSI) caused by DNA mismatch repair (MMR) deficiency is of great significance in the occurrence, diagnosis and treatment of colorectal cancer (CRC). AIM: This study aimed to analyze the relationship between mismatch repair status and clinical characteristics of CRC. METHODS: The histopathological results and clinical characteristics of 2029 patients who suffered from CRC and underwent surgery at two centers from 2018 to 2020 were determined. After screening the importance of clinical characteristics through machine learning algorithms, the patients were divided into deficient mismatch repair (dMMR) and proficient mismatch repair (pMMR) groups based on the immunohistochemistry results and the clinical feature data between the two groups were observed by statistical methods. RESULTS: The dMMR and pMMR groups had significant differences in histologic type, TNM stage, maximum tumor diameter, lymph node metastasis, differentiation grade, gross appearance, and vascular invasion. There were significant differences between the MLH1 groups in age, histologic type, TNM stage, lymph node metastasis, tumor location, and depth of invasion. The MSH2 groups were significantly different in age. The MSH6 groups had significant differences in age, histologic type, and TNM stage. There were significant differences between the PMS2 groups in lymph node metastasis and tumor location. CRC was dominated by MLH1 and PMS2 combined expression loss (41.77%). There was a positive correlation between MLH1 and MSH2 and between MSH6 and PMS2 as well. CONCLUSIONS: The proportion of mucinous adenocarcinoma, protruding type, and poor differentiation is relatively high in dMMR CRCs, but lymph node metastasis is rare. It is worth noting that the expression of MMR protein has different prognostic significance in different stages of CRC disease.

Long-term survivals of immune checkpoint inhibitors as neoadjuvant and adjuvant therapy in dMMR/MSI-H colorectal and gastric cancers.

BACKGROUND: The long-term survival benefit of immune checkpoint inhibitors (ICIs) in neoadjuvant and adjuvant settings is unclear for colorectal cancers (CRC) and gastric cancers (GC) with deficiency of mismatch repair (dMMR) or microsatellite instability-high (MSI-H). METHODS: This retrospective study enrolled patients with dMMR/MSI-H CRC and GC who received at least one dose of neoadjuvant ICIs (neoadjuvant cohort, NAC) or adjuvant ICIs (adjuvant cohort, AC) at 17 centers in China. Patients with stage IV disease were also eligible if all tumor lesions were radically resectable. RESULTS: In NAC (n = 124), objective response rates were 75.7% and 55.4%, respectively, in CRC and GC, and pathological complete response rates were 73.4% and 47.7%, respectively. The 3-year disease-free survival (DFS) and overall survival (OS) rates were 96% (95%CI 90-100%) and 100% for CRC (median follow-up [mFU] 29.4 months), respectively, and were 84% (72-96%) and 93% (85-100%) for GC (mFU 33.0 months), respectively. In AC (n = 48), the 3-year DFS and OS rates were 94% (84-100%) and 100% for CRC (mFU 35.5 months), respectively, and were 92% (82-100%) and 96% (88-100%) for GC (mFU 40.4 months), respectively. Among the seven patients with distant relapse, four received dual blockade of PD1 and CTLA4 combined with or without chemo- and targeted drugs, with three partial response and one progressive disease. CONCLUSION: With a relatively long follow-up, this study demonstrated that neoadjuvant and adjuvant ICIs might be both associated with promising DFS and OS in dMMR/MSI-H CRC and GC, which should be confirmed in further randomized clinical trials.

Homopolymer switches mediate adaptive mutability in mismatch repair-deficient colorectal cancer.

Mismatch repair (MMR)-deficient cancer evolves through the stepwise erosion of coding homopolymers in target genes. Curiously, the MMR genes MutS homolog 6 (MSH6) and MutS homolog 3 (MSH3) also contain coding homopolymers, and these are frequent mutational targets in MMR-deficient cancers. The impact of incremental MMR mutations on MMR-deficient cancer evolution is unknown. Here we show that microsatellite instability modulates DNA repair by toggling hypermutable mononucleotide homopolymer runs in MSH6 and MSH3 through stochastic frameshift switching. Spontaneous mutation and reversion modulate subclonal mutation rate, mutation bias and HLA and neoantigen diversity. Patient-derived organoids corroborate these observations and show that MMR homopolymer sequences drift back into reading frame in the absence of immune selection, suggesting a fitness cost of elevated mutation rates. Combined experimental and simulation studies demonstrate that subclonal immune selection favors incremental MMR mutations. Overall, our data demonstrate that MMR-deficient colorectal cancers fuel intratumor heterogeneity by adapting subclonal mutation rate and diversity to immune selection.

Expression patterns of mismatch repair proteins in cervical cancer uncover independent prognostic value of MSH-2.

OBJECTIVE: Although early-detected cervical cancer is associated with good survival, the prognosis for late-stage disease is poor and treatment options are sparse. Mismatch repair deficiency (MMR-D) has surfaced as a predictor of prognosis and response to immune checkpoint inhibitor(s) in several cancer types, but its value in cervical cancer remains unclear. This study aimed to define the prevalence of MMR-D in cervical cancer and assess the prognostic value of MMR protein expression. METHODS: Expression of the MMR proteins MLH-1, PMS-2, MSH-2, and MSH-6 was investigated by immunohistochemical staining in a prospectively collected cervical cancer cohort (n=508) with corresponding clinicopathological and follow-up data. Sections were scored as either loss or intact expression to define MMR-D, and by a staining index, based on staining intensity and area, evaluating the prognostic potential. RNA and whole exome sequencing data were available for 72 and 75 of the patients and were used for gene set enrichment and mutational analyses, respectively. RESULTS: Five (1%) tumors were MMR-deficient, three of which were of neuroendocrine histology. MMR status did not predict survival (HR 1.93, p=0.17). MSH-2 low (n=48) was associated with poor survival (HR 1.94, p=0.02), also when adjusting for tumor stage, tumor type, and patient age (HR 2.06, p=0.013). MSH-2 low tumors had higher tumor mutational burden (p=0.003) and higher frequency of (frameshift) mutations in the double-strand break repair gene RAD50 (p<0.01). CONCLUSION: MMR-D is rare in cervical cancer, yet low MSH-2 expression is an independent predictor of poor survival.

Clinical performance of the TrueMark™ MSI assay for microsatellite instability detection in a Chinese colorectal cancer cohort.

BACKGROUND: Microsatellite instability (MSI) and mismatch repair (MMR) detection is valuable in assessing prognosis and treatment options. However, the conventional detection methods such as immunohistochemistry (IHC) are limited by not fully consistent results as well as a long turnaround time. TrueMark™ MSI Assay is a novel solution for MSI analysis, but lack of research support in the Chinese colorectal cancer (CRC) patients. MATERIALS AND METHODS: 60 dMMR and 60 pMMR CRC samples identified by IHC were collected and their MSI status were detected using TrueMark™ MSI assay with an expanded panel of 13 markers. The overall performance and diagnostic concordance between TrueMark™ MSI test and MMR IHC analysis were assessed and analyzed. RESULTS: According to the TrueMark™ test, 55 out of the 120 (45.8 %) CRCs were identified as MSI-high (MSI-H) with an instability at ≥ 4/13 markers. Compared with the MMR IHC analysis, an overall percent agreement of 94.2 % and a Kappa of 0.883 were achieved. For the seven inconsistent samples, tumor mutation burden analysis was performed and the results supported the diagnosis by TrueMark™ test. To confirm the robustness of the above findings, a validation was performed in an independent cohort comprising 51 consecutive CRCs. Furthermore, an optimized panel composed of NR-21, NR-24, NR-27, ABI-16, ABI-17 and ABI-20B was developed by multivariate logistic regression model, and showed 100 % agreement with the 13-marker panel for MSI detection in both the derivation and validation sets. CONCLUSION: TrueMark™ MSI provides a fast, reliable and highly automated solution to MSI detection in Chinese CRC patients, and the new 6-marker panel we established shows promise deserving further evaluation.

Immune predictors of response to immune checkpoint inhibitors in mismatch repair-deficient endometrial cancer.

BACKGROUND: Patients with mismatch repair-deficient (MMRd) endometrial cancer (EC) can derive great benefit from immune checkpoint inhibitors (ICI). However not all responses and predictors of primary resistance are lacking. METHODS: We compared the immune tumor microenvironment of MMRd EC ICI-responders (Rs) and ICI non-responders (NRs), using spatial multiplexed immune profiling and unsupervised hierarchical clustering analysis. RESULTS: Overall, NRs exhibited drastically lower CD8+, absent terminally differentiated T cells, lack of mature tertiary lymphoid structures and dendritic cells, as well as loss of human leukocyte antigen class I. However, no single marker could predict R versus NR with confidence. Clustering analysis identified a combination of four immune features that demonstrated that accurately predicted ICI response, with a discriminative power of 92%. Finally, 80% of NRs lacked programmed death-ligand 1, however, 60% exhibited another actionable immune checkpoint (T-cell immunoglobulin and mucin containing protein-3, indoleamine 2,3-dioxygenase 1, or lymphocyte activation gene 3). CONCLUSIONS: These findings underscore the potential of immune tumor microenvironment features for identifying patients with MMRd EC and primary resistance to ICI who should be oriented towards trials testing novel immunotherapeutic combinations.

A Subset of Microsatellite Unstable Cancer Genomes Prone to Short Insertions over Deletions Is Associated with Elevated Anticancer Immunity.

Deficiencies in DNA mismatch repair (MMRd) leave characteristic footprints of microsatellite instability (MSI) in cancer genomes. We used data from the Cancer Genome Atlas and International Cancer Genome Consortium to conduct a comprehensive analysis of MSI-associated cancers, focusing on indel mutational signatures. We classified MSI-high genomes into two subtypes based on their indel profiles: deletion-dominant (MMRd-del) and insertion-dominant (MMRd-ins). Compared with MMRd-del genomes, MMRd-ins genomes exhibit distinct mutational and transcriptomic features, including a higher prevalence of T>C substitutions and related mutation signatures. Short insertions and deletions in MMRd-ins and MMRd-del genomes target different sets of genes, resulting in distinct indel profiles between the two subtypes. In addition, indels in the MMRd-ins genomes are enriched with subclonal alterations that provide clues about a distinct evolutionary relationship between the MMRd-ins and MMRd-del genomes. Notably, the transcriptome analysis indicated that MMRd-ins cancers upregulate immune-related genes, show a high level of immune cell infiltration, and display an elevated neoantigen burden. The genomic and transcriptomic distinctions between the two types of MMRd genomes highlight the heterogeneity of genetic mechanisms and resulting genomic footprints and transcriptomic changes in cancers, which has potential clinical implications.

FANCD2 counteracts O6-methylguanine-induced mismatch repair-dependent apoptosis.

BACKGROUND: Sn1-type alkylating agents methylate the oxygen atom on guanine bases thereby producing O6-methylguanine. This modified base could pair with thymine and cytosine, resulting in the formation of O6-methylguanine/thymine mismatch during DNA replication, recognized by the mismatch repair (MMR) complex, which then initiates the DNA damage response and subsequent apoptotic processes. In our investigation of the molecular mechanisms underlying MMR-dependent apoptosis, we observed FANCD2 modification upon the activity of alkylating agent N-methyl-N-nitrosourea (MNU). This observation led us to hypothesize a relevant role for FANCD2 in the apoptosis induction process. METHODS AND RESULTS: We generated FANCD2 knockout cells using the CRISPR/Cas9 method in the human cervical cancer cell line HeLa MR. FANCD2-deficient cells exhibited MNU hypersensitivity. Upon MNU exposure, FANCD2 colocalized with the MMR complex. MNU-treated FANCD2 knockout cells displayed severe S phase delay followed by increased G2/M arrest and MMR-dependent apoptotic cell death. Moreover, FANCD2 knockout cells exhibited impaired CtIP and RAD51 recruitment to the damaged chromatin and DNA double-strand break accumulation, indicated by simultaneously observed increased γH2AX signal and 53BP1 foci. CONCLUSIONS: Our data suggest that FANCD2 is crucial for recruiting homologous recombination factors to the sites of the MMR-dependent replication stress to resolve the arrested replication fork and counteract O6-methylguanine-triggered MMR-dependent apoptosis.

Functional analysis of MMR gene VUS from potential Lynch syndrome patients.

Lynch syndrome is caused by inactivating variants in DNA mismatch repair genes, namely MLH1, MSH2, MSH6 and PMS2. We have investigated five MLH1 and one MSH2 variants that we have identified in Turkish and Tunisian colorectal cancer patients. These variants comprised two small deletions causing frameshifts resulting in premature stops which could be classified pathogenic (MLH1 p.(His727Profs*57) and MSH2 p.(Thr788Asnfs*11)), but also two missense variants (MLH1 p.(Asn338Ser) and p.(Gly181Ser)) and two small, in-frame deletion variants (p.(Val647-Leu650del) and p.(Lys678_Cys680del)). For such small coding genetic variants, it is unclear if they are inactivating or not. We here provide clinical description of the variant carriers and their families, and we performed biochemical laboratory testing on the variant proteins to test if their stability or their MMR activity are compromised. Subsequently, we compared the results to in-silico predictions on structure and conservation. We demonstrate that neither missense alteration affected function, while both deletion variants caused a dramatic instability of the MLH1 protein, resulting in MMR deficiency. These results were consistent with the structural analyses that were performed. The study shows that knowledge of protein function may provide molecular explanations of results obtained with functional biochemical testing and can thereby, in conjunction with clinical information, elevate the evidential value and facilitate clinical management in affected families.

Molecular Classification of Endometrial Cancer and Its Impact on Therapy Selection.

Endometrial cancer (EC) accounts for 90% of uterine cancer cases. It is considered not only one of the most common gynecological malignancies but also one of the most frequent cancers among women overall. Nowadays, the differentiation of EC subtypes is based on immunohistochemistry and molecular techniques. It is considered that patients' prognosis and the implementation of the appropriate treatment depend on the cancer subtype. Patients with pathogenic variants in POLE have the most favorable outcome, while those with abnormal p53 protein have the poorest. Therefore, in patients with POLE mutation, the de-escalation of postoperative treatment may be considered, and patients with abnormal p53 protein should be subjected to intensive adjuvant therapy. Patients with a DNA mismatch repair (dMMR) deficiency are classified in the intermediate prognosis group as EC patients without a specific molecular profile. Immunotherapy has been recognized as an effective treatment method in patients with advanced or recurrent EC with a mismatch deficiency. Thus, different adjuvant therapy approaches, including targeted therapy and immunotherapy, are being proposed depending on the EC subtype, and international guidelines, such as those published by ESMO and ESGO/ESTRO/ESP, include recommendations for performing the molecular classification of all EC cases. The decision about adjuvant therapy selection has to be based not only on clinical data and histological type and stage of cancer, but, following international recommendations, has to include EC molecular subtyping. This review describes how molecular classification could support more optimal therapeutic management in endometrial cancer patients.

[Effects of tumor location and mismatch repair on clinicopathological features and survival for non-metastatic colon cancer: A retrospective, single center, cohort study].

Objective: To analyze the differences in clinicopathological features of colon cancers and survival between patients with right- versus left-sided colon cancers. Methods: This was a retrospective cohort study. Information on patients with colon cancer from January 2016 to August 2020 was collected from the prospective registry database at Peking Union Medical College Hospital . Primary tumors located in the cecum, ascending colon, and proximal two-thirds of the transverse colon were defined as right-sided colon cancers (RCCs), whereas primary tumors located in the distal third of the transverse colon, descending colon, or sigmoid colon were defined as left-sided colon cancers (LCCs). Clinicopathological features were compared using the χ2 test or Mann-Whitney U test. Survival was estimated by Kaplan-Meier curves and the log-rank test. Factors that differed significantly between the two groups were identified by multivariate survival analyses performed with the Cox proportional hazards function. One propensity score matching was performed to eliminate the effects of confounding factors. Results: The study cohort comprised 856 patients, with TNM Stage I disease, 391 (45.7%) with Stage II, and 336 (39.3%) with Stage III, including 442 (51.6%) with LCC and 414 (48.4%) with RCC and 129 (15.1%). Defective mismatch repair (dMMR) was identified in 139 patients (16.2%). Compared with RCC, the proportion of men (274/442 [62.0%] vs. 224/414 [54.1%], χ2=5.462, P=0.019), body mass index (24.2 [21.9, 26.6] kg/m2 vs. 23.2 [21.3, 25.5] kg/m2, U=78,789.0, P<0.001), and well/moderately differentiated cancer (412/442 [93.2%] vs. 344/414 [83.1%], χ2=22.266, P<0.001) were higher in the LCC than the RCC group. In contrast, the proportion of dMMR (40/442 [9.0%] vs. 99/414 [23.9%], χ2=34.721, P<0.001) and combined vascular invasion (106/442[24.0%] vs. 125/414[30.2%], χ2=4.186, P=0.041) were lower in the LCC than RCC group. The median follow-up time for all patients was 48 (range 33, 59) months. The log-rank test revealed no significant differences in disease-free survival (DFS) (P=0.668) or overall survival (OS) (P=0.828) between patients with LCC versus RCC. Cox proportional hazards model showed that dMMR was significantly associated with a longer DFS (HR=0.419, 95%CI: 0.204‒0.862, P=0.018), whereas a higher proportion of T3-4 (HR=2.178, 95%CI: 1.089‒4.359, P=0.028), N+ (HR=2.126, 95%CI: 1.443‒3.133, P<0.001), and perineural invasion (HR=1.835, 95%CI: 1.115‒3.020, P=0.017) were associated with poor DFS. Tumor location was not associated with DFS or OS (all P>0.05). Subsequent analysis showed that RCC patients with dMMR had longer DFS than did RCC patients with pMMR (HR=0.338, 95%CI: 0.146‒0.786, P=0.012). However, the difference in OS between the two groups was not statistically significant (HR=0.340, 95%CI:0.103‒1.119, P=0.076). After propensity score matching for independent risk factors for DFS, the log-rank test revealed no significant differences in DFS (P=0.343) or OS (P=0.658) between patients with LCC versus RCC, whereas patient with dMMR had better DFS (P=0.047) and OS (P=0.040) than did patients with pMMR. Conclusions: Tumor location is associated with differences in clinicopathological features; however, this has no impact on survival. dMMR status is significantly associated with longer survival: this association may be stronger in RCC patients.

Mismatch repair protein deficiency in triple-negative breast carcinomas.

BACKGROUND: Breast cancer, particularly triple-negative breast cancer (TNBC), poses a significant global health burden. Chemotherapy was the mainstay treatment for TNBC patients until immunotherapy was introduced. Studies indicate a noteworthy prevalence (0.2% to 18.6%) of mismatch repair protein (MMRP) deficiency in TNBC, with recent research highlighting the potential of immunotherapy for MMRP-deficient metastatic breast cancer. This study aims to identify MMRP deficiency in TNBC patients using immunohistochemistry. METHODS: A retrospective cohort study design was used and included TNBC patients treated between 2015 and 2021 at King Hussein Cancer Center. Immunohistochemistry was conducted to assess MMRP expression. RESULTS: Among 152 patients, 14 (9.2%) exhibited deficient MMR (dMMR). Loss of PMS2 expression was observed in 13 patients, 5 of whom showed loss of MLH1 expression. Loss of MSH6 and MSH2 expression was observed in one patient. The median follow-up duration was 44 (3-102) months. Despite the higher survival rate (80.8%, 5 years) of dMMR patients than of proficient MMR patients (62.3%), overall survival did not significantly differ between the two groups. CONCLUSION: Approximately 9% of TNBC patients exhibit dMMR. dMMR could be used to predict outcomes and identify patients with TNBC who may benefit from immunotherapy.

Enhanced eMAGE applied to identify genetic factors of nuclear hormone receptor dysfunction via combinatorial gene editing.

Technologies that generate precise combinatorial genome modifications are well suited to dissect the polygenic basis of complex phenotypes and engineer synthetic genomes. Genome modifications with engineered nucleases can lead to undesirable repair outcomes through imprecise homology-directed repair, requiring non-cleavable gene editing strategies. Eukaryotic multiplex genome engineering (eMAGE) generates precise combinatorial genome modifications in Saccharomyces cerevisiae without generating DNA breaks or using engineered nucleases. Here, we systematically optimize eMAGE to achieve 90% editing frequency, reduce workflow time, and extend editing distance to 20 kb. We further engineer an inducible dominant negative mismatch repair system, allowing for high-efficiency editing via eMAGE while suppressing the elevated background mutation rate 17-fold resulting from mismatch repair inactivation. We apply these advances to construct a library of cancer-associated mutations in the ligand-binding domains of human estrogen receptor alpha and progesterone receptor to understand their impact on ligand-independent autoactivation. We validate that this yeast model captures autoactivation mutations characterized in human breast cancer models and further leads to the discovery of several previously uncharacterized autoactivating mutations. This work demonstrates the development and optimization of a cleavage-free method of genome editing well suited for applications requiring efficient multiplex editing with minimal background mutations.

Correlation between immunohistochemical staining and clinicopathological findings in endometrial carcinoma.

OBJECTIVES: To analyze the immunohistochemical staining pattern of mismatch repair (MMR) proteins and p53 in endometrial carcinoma cases, including different subtypes and stages, to gain insights into their role in the pathogenesis and clinical behaviour of this malignancy. METHODS: In this study, we investigate the association between MMR deficiency, p53 mutational status, and clinical outcomes in various subtypes of endometrial carcinoma. The immunohistochemical staining pattern of MMR proteins in 96 cases of endometrial carcinoma have been analyzed, including 72 endometrioid, 14 papillary serous, 5 clear cell, and 5 mixed Müllerian tumor. RESULTS: The results showed that 36 cases were MMR deficient, with the majority being of endometrioid subtype. The p53 immunostain showed a mutational pattern in a subset of cases, with a documented dismal prognosis. However, aforementioned stains failed to predict synchronous or metachronous cancers in 5 patients. CONCLUSION: These findings highlight the importance of MMR and p53 immunohistochemical staining in the classification, and prognosis of endometrial carcinoma.

Neoadjuvant camrelizumab plus apatinib for locally advanced microsatellite instability-high or mismatch repair-deficient colorectal cancer (NEOCAP): a single-arm, open-label, phase 2 study.

BACKGROUND: PD-1 blockade is highly efficacious for mismatch repair-deficient colorectal cancer in both metastatic and neoadjuvant settings. We aimed to explore the activity and safety of neoadjuvant therapy with PD-1 blockade plus an angiogenesis inhibitor and the feasibility of organ preservation in patients with locally advanced mismatch repair-deficient colorectal cancer. METHODS: We initiated a single-arm, open-label, phase 2 trial (NEOCAP) at Sun Yat-sen University Cancer Center and the Provincial Hospital of Traditional Chinese Medicine, Guangzhou, China. Patients aged 18-75 years with untreated mismatch repair-deficient or microsatellite instability-high or POLE/POLD1-mutated locally advanced colorectal cancer (cT3 or N+ for rectal cancer, and T3 with invasion ≥5mm or T4, with or without N+ for colon cancer) and an Eastern Cooperative Oncology Group performance score of 0-1 were enrolled and given 200 mg camrelizumab intravenously on day 1 and 250 mg apatinib orally from day 1-14, every 3 weeks for 3 months followed by surgery or 6 months if patients did not have surgery. Patients who had a clinical complete response did not undergo surgery and proceeded with a watch-and-wait approach. The primary endpoint was the proportion of patients with a pathological or clinical complete response. Eligible enrolled patients who received at least one cycle of neoadjuvant treatment and had at least one tumour response assessment following the baseline assessment were included in the activity analysis, and patients who received at least one dose of study drug were included in the safety analysis. The study is registered with ClinicalTrials.gov (NCT04715633) and is ongoing. FINDINGS: Between Sept 29, 2020, and Dec 15, 2022, 53 patients were enrolled; one patient was excluded from the activity analysis because they were found to be mismatch repair-proficient and microsatellite-stable. 23 (44%) patients were female and 29 (56%) were male. The median follow-up was 16·4 (IQR 10·5-23·5) months. 28 (54%; 95% CI 35-68) patients had a clinical complete response and 24 of these patients were managed with a watch-and-wait approach, including 20 patients with colon cancer and multiple primary colorectal cancer. 23 (44%) of 52 patients underwent surgery for the primary tumour, and 14 (61%; 95% CI 39-80) had a pathological complete response. 38 (73%; 95% CI 59-84) of 52 patients had a complete response. Grade 3-5 adverse events occurred in 20 (38%) of 53 patients; the most common were increased aminotransferase (six [11%]), bowel obstruction (four [8%]), and hypertension (four [8%]). Drug-related serious adverse events occurred in six (11%) of 53 patients. One patient died from treatment-related immune-related hepatitis. INTERPRETATION: Neoadjuvant camrelizumab plus apatinib show promising antitumour activity in patients with locally advanced mismatch repair-deficient or microsatellite instability-high colorectal cancer. Immune-related adverse events should be monitored with the utmost vigilance. Organ preservation seems promising not only in patients with rectal cancer, but also in those with colon cancer who have a clinical complete response. Longer follow-up is needed to assess the oncological outcomes of the watch-and-wait approach. FUNDING: The National Natural Science Foundation of China, Guangdong Basic and Applied Basic Research Foundation, and the Cancer Innovative Research Program of Sun Yat-sen University Cancer Center. TRANSLATION: For the Chinese translation of the abstract see Supplementary Materials section.

PD-1 blockade enhances the effect of targeted chemotherapy on locally advanced pMMR/MSS colorectal cancer.

BACKGROUND: Patients with DNA mismatch repair-proficient/microsatellite stable (pMMR/MSS) colorectal cancer (CRC), which accounts for 85% of all CRC cases, display a poor respond to immune checkpoint inhibitors (i.e., anti-PD-1 antibodies). pMMR/MSS CRC patients with locally advanced cancers need effective combined therapies. METHODS: In this pilot study, we administered six preoperative doses of each 2-week cycle of the anti-PD-1 antibody sintilimab (at a fixed dose of 200 mg), oxaliplatin, and 5-FU/CF (mFOLFOX6) combined with five doses of bevacizumab (the number of doses was reduced to prevent surgical delays) to patients with cT4NxM0 colon or upper rectal cancers. And radical surgery was performed approximately 2 weeks after the last dose of neoadjuvant therapy. The primary endpoint was a pathologic complete response (pCR). We also evaluated major pathologic response (MPR, ≤10% residual viable tumor), radiological and pathological regression, safety, and tumor mutation burden (TMB), and tumor microenvironment (TME) characteristics. RESULTS: By the cutoff date (September 2023), 22 patients with cT4NxM0 pMMR/MSS colon or upper rectal cancers were enrolled and the median follow-up was 24.7 months (IQR: 21.1-26.1). All patients underwent R0 surgical resection without treatment-related surgical delays. pCR occurred in 12 of 22 resected tumors (54.5%) and MPR occurred in 18 of 22 (81.8%) patients. At the cutoff date, all patients were alive, and 21/22 were recurrence-free. Treatment-related adverse events of grade 3 or higher occurred in of 2/22 (9.1%) patients. Among the pCR tumors, two were found to harbor POLE mutations. The degree of pathological regression was significantly greater than that of radiological regression (p = 1.35 × 10-8). The number of CD3+/CD4+ cells in the tumor and stroma in pretreated biopsied tissues was markedly lower in pCR tumors than in non-pCR tumors (p = 0.038 and p = 0.015, respectively). CONCLUSIONS: Neoadjuvant sintilimab combined with bevacizumab and mFOLFOX6 was associated with few side effects, did not delay surgery, and led to pCR and non-pCR in 54.5% and 81.8% of the cases, respectively. Downregulation of CD3/CD4 expression in the tumor and stroma is related to pCR. However, the molecular mechanisms underlying PD-1 blockade-enhanced targeted chemotherapy require further investigation.