DNA double-strand breaks represent a common type of serious DNA damage in living organisms, causing instability of the genome and leading to cell death. Homologous recombination and non-homologous end-joining (NHEJ) are the two main ways to repair DNA double-strand breaks. The core components involved in the NHEJ pathway are highly conserved in both yeast and humans. A few bacteria such as Mycobacterium, Pseudomonas aeruginosa, and Bacillus subtilis also have the NHEJ mechanism. NHEJ plays a key role in the double strand repair of Mycobacterium in latency. This paper summarizes the mechanism and important components of NHEJ in Mycobacterium, introduces the application of NHEJ in gene editing, and reviews the research progress of the NHEJ pathway in Mycobacterium. We hope to bring new insights into the molecular mechanism and provide clues for the application of NHEJ in Mycobacterium.
DNA End-Joining Repair/physiology* ; Gene Editing/methods* ; Mycobacterium/physiology* ; DNA Breaks, Double-Stranded ; Humans

Rectal cancer is one of the most common malignant tumors in China, with more than half of patients diagnosed at the locally advanced stage. Currently, the standard treatment for locally advanced rectal cancer (LARC) primarily involves neoadjuvant chemoradiotherapy followed by radical surgery. The advent of immune checkpoint inhibitors has revolutionized the neoadjuvant treatment landscape for mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) rectal cancer. However, most rectal cancer patients exhibit mismatch repair-proficient/microsatellite stable (pMMR/MSS) status and show poor responsiveness to immunotherapy. In recent years, multiple studies have demonstrated that neoadjuvant short-course radiotherapy followed by chemotherapy and immunotherapy can improve the pathological complete response rate in pMMR/MSS LARC patients. Nevertheless, controversies persist regarding patient selection, efficacy evaluation, adverse event management, postoperative adjuvant therapy, and follow-up strategies. Considering the Colorectal Surgery Group of the Surgery Branch of the Chinese Medical Association, in collaboration with the Colorectal and Anal Surgery Committee of the Chinese Research Hospital Association, the Chinese Colorectal Cancer Clinical Research Collaborative Group, and related experts, has developed this consensus document by referencing domestic and international research advancements. The aim is to provide standardized guidance for the clinical application of this treatment approach.
Humans ; Rectal Neoplasms/genetics* ; Neoadjuvant Therapy ; Immunotherapy ; DNA Mismatch Repair ; Microsatellite Instability ; Consensus ; Combined Modality Therapy

Oroxylin A (OA), a natural compound extracted from Scutellaria baicalensis, demonstrates preventive potential against ultraviolet B (UVB)-induced non-melanoma skin cancer (NMSC), the most prevalent cancer worldwide with increasing incidence. Utilizing SKH-1 hairless mice exposed to UVB, this study showed that OA delayed NMSC onset and alleviated acute skin damage. Mechanistic investigations revealed its dual action: inhibiting inflammation and enhancing nucleotide excision repair (NER) by stabilizing XPA, a crucial deoxyribonucleic acid (DNA) repair protein. This stabilization occurred through OA's interaction with glucose-regulated protein 94 (GRP94), which disrupted murine double minute 2 (MDM2)-mediated XPA ubiquitination and proteasomal degradation. By maintaining XPA levels, OA expedited photoproduct clearance and diminished genomic instability, ultimately impeding NMSC development. These findings suggest OA as a promising chemopreventive agent targeting the GRP94/MDM2-XPA axis to counteract UVB-induced carcinogenesis.
Animals ; Ultraviolet Rays/adverse effects* ; Skin Neoplasms/prevention & control* ; Flavonoids/pharmacology* ; Mice ; Xeroderma Pigmentosum Group A Protein/genetics* ; Humans ; Proto-Oncogene Proteins c-mdm2/genetics* ; DNA Repair/drug effects* ; Scutellaria baicalensis/chemistry* ; Mice, Hairless ; Skin/radiation effects*

The accumulation of deoxyribonucleic acid (DNA) oxidative damage mediated by reactive oxygen species (ROS) is closely associated with liver diseases. 8-Oxoguanine (8-OxoG), a prevalent DNA oxidation product, plays a significant role in liver disease progression. The base excision repair (BER) pathway, comprising over 30 proteins including 8-OxoG DNA glycosylase1 (OGG1), MutY homolog (MUTYH), and MutT homolog protein 1 (MTH1), is responsible for the clearance and mismatch repair of 8-OxoG. Abnormally high levels of 8-OxoG and dysregulated expression and function of 8-OxoG repair enzymes contribute to the onset and development of liver diseases. Consequently, targeting the 8-OxoG production and repair system with agonists or inhibitors may offer a promising approach to liver disease treatment. This review summarizes the impact of 8-OxoG accumulation and dysregulated repair enzymes on various liver diseases, including viral liver disease, alcoholic liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), cholestatic liver disease (CLD), liver fibrosis, cirrhosis, and liver cancer. Additionally, we review natural constituents as potential therapeutic agents that regulate 8-OxoG production, repair enzymes, and repair system-related signal pathways in oxidative damage-induced liver diseases.
Humans ; Liver Diseases/genetics* ; Biological Products/pharmacology* ; DNA Repair/drug effects* ; Guanine/metabolism* ; Animals ; Disease Progression ; DNA Damage ; Oxidative Stress

Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPis) have emerged as critical agents for cancer therapy. By inhibiting the catalytic activity of PARP enzymes and trapping them in the DNA, PARPis disrupt DNA repair, ultimately leading to cell death, particularly in cancer cells with homologous recombination repair deficiencies, such as those harboring BRCA mutations. This review delves into the mechanisms of action of PARPis in anticancer treatments, including the inhibition of DNA repair, synthetic lethality, and replication stress. Furthermore, the clinical applications of PARPis in various cancers and their adverse effects as well as their combinations with other therapies and the mechanisms underlying resistance are summarized. This review provides comprehensive insights into the role and mechanisms of PARP and PARPis in DNA repair, with a particular focus on the potential of PARPi-based therapies in precision medicine for cancer treatment.
Humans ; Poly(ADP-ribose) Polymerase Inhibitors/therapeutic use* ; Neoplasms/genetics* ; DNA Repair/drug effects* ; Animals ; Antineoplastic Agents/therapeutic use*

BACKGROUND

Approximately 15% of colorectal cancers exhibit deficient mismatch repair (dMMR) status, and these cases have a better prognosis and are less prone to metastasis. Moreover, dMMR is associated with an improved response to immune checkpoint inhibitors. Currently, local data on the MMR status of colorectal cancer patients remains scant.

The proponents aimed to determine the MMR status among colorectal cancer patients in a Philippine tertiary hospital.

This is a descriptive cross-sectional study that included 42 patients with colorectal cancer seen at the Chinese General Hospital and Medical Center (CGHMC) from January 2021 to June 2024. Data was collected via retrospective review of histopathologic reports.

Forty-two (42) patients were included in the study. The mean age of included patients was 61.8 years, and most were males. Half had well-differentiated tumor grade, and the most common tumor locations were rectum (38%) and sigmoid (36%). Three patients (7.14%; 95% CI:1.50-19.48%) were considered deficient. Tumor locations in dMMR patients were the cecum, descending colon, and rectum. Compared to MMR-proficient, dMMR patients had a lower mean age (63.1 vs. 45.7 years). Also, a higher proportion of males (13%) were dMMR than females (0%).

dMMR is uncommon among the colorectal cancer cases in this study, and was only seen at the cecum, descending colon, and rectum. Descriptive analysis revealed that patients with dMMR were younger than MMR-proficient patients. Moreover, a higher proportion of males were dMMR than females. Larger, multicenter studies are warranted to validate these preliminary findings and guide future clinical decision-making.

Immunotherapy has been one of the hot topics in the field of colorectal cancer research in recent years. Patients with microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) are the main beneficiaries of immunotherapy. The response rate of patients with dMMR/MSI-H colorectal cancer receiving neoadjuvant immunotherapy is nearly 100%, of which the pathological complete response rate approximately accounts for 60%-67%. The prospect of neoadjuvant immunotherapy in dMMR or MSI-H colorectal cancer patients, especially in the rectal cancer patients, lies in achieving sustainable clinical complete response so as to achieve organ preservation and avoid adverse effects on reproductive, sexual, bowel and bladder function after surgery and radiotherapy. Studies have shown that part of the colorectal cancer patients of microsatellite stability (MSS) or mismatch repair proficient (pMMR) can respond to neoadjuvant immunotherapy in combination with other treatment methods such as radiotherapy and chemotherapy. In pMMR or MSS colorectal cancer, optimizing neoadjuvant immunotherapy regimens and finding effective efficacy prediction biomarkers are important research directions. In neoadjuvant immunotherapy, overcoming primary and secondary resistance and identifying the pseudoprogression and hyperprogression of neoadjuvant immunotherapy are clinical challenges that require attention. This paper comprehensively reviews the research progress, controversies,challenges and future research directions of neoadjuvant immunotherapy (mainly immune checkpoint inhibitors) in colorectal cancer.
Humans ; Neoadjuvant Therapy/methods* ; Colorectal Neoplasms/drug therapy* ; Colonic Neoplasms/pathology* ; Immunotherapy/methods* ; DNA Mismatch Repair ; Microsatellite Instability

Objective To study the pathological types,expression of mismatch repair protein,human epidermal growth factor receptor 2(HER2),and Pan-TRK,and Epstein-Barr virus(EBV)infection in patients with colorectal cancer resected in Tibet. Methods A total of 79 patients with colorectal cancer resected in Tibet Autonomous Region People's Hospital from December 2013 to July 2021 were enrolled in this study.The clinical and pathological data of the patients were collected.The expression of mismatch repair protein,HER2,and Pan-TRK was detected by immunohistochemical(IHC)staining,and detection of HER2 gene by fluorescence in situ hybridization(FISH)in the patients with HER2 IHC results of 2+ or above.EBV was detected by in situ hybridization with EBV-encoded small RNA. Results A total of 79 colorectal cancer patients were included in this study,with the male-to-female ratio of 1.26:1 and the mean age of(57.06±12.74)years(24-83 years).Among them,4 patients received preoperative neoadjuvant therapy.Colonic cancer and rectal cancer occurred in 57(57/79,72.15%,including 31 and 26 in the right colon and left colon,respectively)and 22(22/79,27.85%)patients,respectively.The maximum diameter of tumor varied within the range of 1-20 cm,with the mean of(6.61±3.33)cm.Among the 79 colorectal cancer patients,75(75/79,94.94%)patients showed adenocarcinoma.Lymph node metastasis occurred in 12(12/21,57.14%)out of the 21 patients with severe tumor budding,13(13/23,56.52%)out of the 23 patients with moderate tumor budding,and 2(2/31,6.45%)out of the 31 patients with mild tumor budding,respectively.The lymph node metastasis rate showed differences between the patients with severe/moderate tumor budding and the patients with mild tumor budding(all P<0.001).The IHC staining showed that mismatch repair protein was negative in 10(10/65,15.38%)patients,including 5 patients with both MSH2 and MSH6 negative,4 patients with both MLH1 and PMS2 negative,and 1 patient with MSH6 negative.Pan-TRK was negative in 65 patients.The IHC results of HER2 showed 0 or 1+ in 60 patients and 2+ in 5 patients.FISH showed no positive signal in the 5 patients with HER2 IHC results of 2+.The detection with EBV-encoded small RNA showed positive result in 1(1/65,1.54%)patient. Conclusions Non-specific adenocarcinoma of the right colon is the most common in the patients with colorectal cancer resected in Tibet,and 15% of the patients showed mismatch repair protein defects.EBV-associated colorectal carcer is rare,Pan-TRK expression and HER2 gene amplification are seldom.The colorectal cancer patients with moderate and severe tumor budding are more likely to have lymph node metastasis.
Adult ; Aged ; Female ; Humans ; Male ; Middle Aged ; Adenocarcinoma ; Biomarkers, Tumor/genetics* ; Colorectal Neoplasms/pathology* ; DNA Mismatch Repair ; DNA-Binding Proteins/genetics* ; Epstein-Barr Virus Infections/diagnosis* ; Herpesvirus 4, Human/metabolism* ; In Situ Hybridization, Fluorescence ; Lymphatic Metastasis ; Tibet ; Young Adult ; Aged, 80 and over

BACKGROUND: Microsatellite instability (MSI) is a key biomarker for cancer immunotherapy and prognosis. Integration of MSI testing into a next-generation-sequencing (NGS) panel could save tissue sample, reduce turn-around time and cost, and provide MSI status and comprehensive genomic profiling in single test. We aimed to develop an MSI calling model to detect MSI status along with the NGS panel-based profiling test using tumor-only samples. METHODS: From January 2019 to December 2020, a total of 174 colorectal cancer (CRC) patients were enrolled, including 31 MSI-high (MSI-H) and 143 microsatellite stability (MSS) cases. Among them, 56 paired tumor and normal samples (10 MSI-H and 46 MSS) were used for modeling, and another 118 tumor-only samples were used for validation. MSI polymerase chain reaction (MSI-PCR) was performed as the gold standard. A baseline was built for the selected microsatellite loci using the NGS data of 56 normal blood samples. An MSI detection model was constructed by analyzing the NGS data of tissue samples. The performance of the model was compared with the results of MSI-PCR. RESULTS: We first intersected the target genomic regions of the NGS panels used in this study to select common microsatellite loci. A total of 42 loci including 23 mononucleotide repeat sites and 19 longer repeat sites were candidates for modeling. As mononucleotide repeat sites are more sensitive and specific for detecting MSI status than sites with longer length motif and the mononucleotide repeat sites performed even better than the total sites, a model containing 23 mononucleotide repeat sites was constructed and named Colorectal Cancer Microsatellite Instability test (CRC-MSI). The model achieved 100% sensitivity and 100% specificity when compared with MSI-PCR in both training and validation sets. Furthermore, the CRC-MSI model was robust with the tumor content as low as 6%. In addition, 8 out of 10 MSI-H samples showed alternations in the four mismatch repair genes ( MLH1 , MSH2 , MSH6 , and PMS2 ). CONCLUSION MSI status can be accurately determined along the targeted NGS panels using only tumor samples. The performance of mononucleotide repeat sites surpasses loci with longer repeat motif in MSI calling.
Humans ; Microsatellite Instability ; Colorectal Neoplasms/diagnosis* ; Microsatellite Repeats/genetics* ; DNA Mismatch Repair

OBJECTIVE: To analyze the differences and characteristics of microsatellite instability (MSI) in endometrial cancer (EMC), by using colorectal cancer (CRC) as control. METHODS: In the study, 228 cases of EMC were collected. For comparative analysis, 770 cases of CRC were collected. Mismatch repair (MMR) expression was detected by immunohistochemistry (IHC), and microsatellite instability (MSI) was analyzed by PCR and capillary electrophoresis fragment analysis (MSI-PCR). MSI-PCR was detected using five mononucleotide repeat markers: BAT-25, BAT-26, NR-21, NR-24, and MONO-27. RESULTS: In EMC, we found 27.19% (62/228) of deficient mismatch repair (dMMR) using IHC, significantly higher than CRC (7.79%, 60/770). Meanwhile, subclonal expression of MMR protein was found in 4 cases of dMMR-EMC and 2 cases of dMMR-CRC. According to the criteria of major micro-satellite shift, we found 16.23% (37/228) of MSI-high (MSI-H), 2.63% (6/228) of MSI-low (MSI-L), and 81.14% (185/228) of microsatellite stability (MSS) in EMC using MSI-PCR. The discor-dance rate between MMR-IHC and MSI-PCR in EMC was 11.84% (27/228). In CRC, we found 8.05% (62/770) of MSI-H, 0.13% (1/770) of MSI-L, and 91.82% (707/770) of MSS. The discordance rate between MMR-IHC and MSI-PCR in CRC was only 0.52% (4/770). However, according to the criteria of minimal microsatellite shift, 12 cases of EMC showed minimal microsatellite shift including 8 cases of dMMR/MSS and 4 cases of dMMR/MSI-L and these cases were ultimately evaluated as dMMR/MSI-H. Then, 21.49% (49/228) of EMC showed MSI-H and the discordance rate MMR-IHC and MSI-PCR in EMC decreased to 6.58% (15/228). No minimal microsatellite shift was found in CRC. Compared with EMC group with major microsatellite shift, cases with minimal microsatellite shift showed younger age, better tumor differentiation, and earlier International Federation of Gynecology and Obstetrics (FIGO) stage. There were significant differences in histological variant and FIGO stage between the two groups (P < 0.001, P=0.006). CONCLUSION EMC was more prone to minimal microsatellite shift, which should not be ignored in the interpretation of MSI-PCR results. The combined detection of MMR-IHC and MSI-PCR is the most sensitive and specific method to capture MSI tumors.
Female ; Humans ; Microsatellite Instability ; Colorectal Neoplasms ; Microsatellite Repeats ; Endometrial Neoplasms ; DNA Mismatch Repair