Chlorambucil (CLB) belongs to the class of nitrogen mustards (NMs), which are highly reactive bifunctional alkylating agents and were the first chemotherapeutic agents developed. They form DNA interstrand crosslinks (ICLs), which cause a blockage of DNA strand separation, inhibiting essential processes in DNA metabolism like replication and transcription. In fast replicating cells, e.g., tumor cells, this can induce cell death. The upregulation of ICL repair is thought to be a key factor for the resistance of tumor cells to ICL-inducing cytostatic agents including NMs. To monitor induction and repair of CLB-induced ICLs, we adjusted the automated reversed fluorometric analysis of alkaline DNA unwinding assay (rFADU) for the detection of ICLs in adherent cells. For the detection of monoalkylated DNA bases we established an LC-MS/MS method. We performed a comparative analysis of adduct formation and removal in five human cell lines and in peripheral blood mononuclear cells (PBMCs) after treatment with CLB. Dose-dependent increases in adduct formation were observed, and suitable treatment concentrations were identified for each cell line, which were then used for monitoring the kinetics of adduct formation. We observed significant differences in the repair kinetics of the cell lines tested. For example, in A2780 cells, hTERT immortalized VH10 cells, and in PBMCs a time-dependent repair of the two main monoalkylated DNA-adducts was confirmed. Regarding ICLs, repair was observed in all cell systems except for PBMCs. In conclusion, LC-MS/MS analyses combined with the rFADU technique are powerful tools to study the molecular mechanisms of NM-induced DNA damage and repair. By applying these methods to a spectrum of human cell systems of different origin and transformation status, we obtained insight into the cell-type specific repair of different CLB-induced DNA lesions, which may help identify novel resistance mechanisms of tumors and define molecular targets for therapeutic interventions.

UNASSIGNED: Ovarian cancer is the 8th deadliest common cancer in women around the world. Almost all ovarian cancer patients would experience chemoresistance, recurrence, and poor prognosis after cytoreductive surgery and platinum-based chemotherapy. Chemoresistant cancer cells have characteristic expressions of cancer stem cell proteins (CSCs) CD44+/CD24-, RAD6 and DDB2. The increased expression of CD44+/CD24-, RAD6, and decreased DDB2 are believed to be associated with chemoresistance, recurrence, and poor prognosis of the disease. Thus, this study\'s objective is to analyze the correlation between the expression of CD44+/CD24-, RAD6 and DDB2 with ovarian cancer chemoresistance.
UNASSIGNED: This study was conducted with a prospective cohort of 64 patients who is divided into two groups (32 patients in each group) at the Obstetrics-gynecology and pathology department of Cipto Mangunkusumo, Tarakan, Dharmais, and Fatmawati Hospital. All suspected ovarian cancer patients underwent cytoreductive debulking and histopathological examination. Chemotherapy was given for six series followed by six months of observation. After the observation, we determined the therapy\'s response with the RECIST Criteria (Response Criteria in Solid Tumors) and then classified the results into chemoresistant or chemosensitive groups. Flow cytometry blood tests were then performed to examine the expression of CD44+/CD24-, RAD6 and DDB2.
UNASSIGNED: There was a significant relationship between increased levels of CD44+/CD24-, and RAD6 (p < 0.05) levels with the chemoresistance of ovarian cancer. The logistic regression test showed that the CD44+/CD24- was better marker.
UNASSIGNED: These results indicate that CD44+/CD24 and RAD6 expressions are significantly associated with ovarian cancer chemoresistance, and CD44+/CD24- is the better marker to predict ovarian cancer chemoresistance.

Genomic instability remains an enabling feature of cancer and promotes malignant transformation. Alterations of DNA damage response (DDR) pathways allow genomic instability, generate neoantigens, upregulate the expression of programmed death ligand 1 (PD-L1) and interact with signaling such as cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling. Here, we review the basic knowledge of DDR pathways, mechanisms of genomic instability induced by DDR alterations, impacts of DDR alterations on immune system, and the potential applications of DDR alterations as biomarkers and therapeutic targets in cancer immunotherapy.

Transcription is a potential threat to genome integrity, and transcription-associated DNA damage must be repaired for proper messenger RNA (mRNA) synthesis and for cells to transmit their genome intact into progeny. For a wide range of structurally diverse DNA lesions, cells employ the highly conserved nucleotide excision repair (NER) pathway to restore their genome back to its native form. Recent evidence suggests that NER factors function, in addition to the canonical DNA repair mechanism, in processes that facilitate mRNA synthesis or shape the 3D chromatin architecture. Here, these findings are critically discussed and a working model that explains the puzzling clinical heterogeneity of NER syndromes highlighting the relevance of physiological, transcription-associated DNA damage to mammalian development and disease is proposed.

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The role of environmental factors and genetic susceptibility in the development of colon cancer (CC) has been already proven, but the role of gene polymorphisms in modifying the risk of environmental factors such as nutritional factors is still unknown. This study aimed to investigate the effect of polymorphisms of involved genes in the association between red meat consumption and the development of CC. The present review was carried out using keywords such as polymorphism and/or protein and/or red meat and/or processed meat and/or colon cancer. PubMed and Science Direct databases were used to collect all related articles published from 2001 to 2017. The presence of SNP in the coding genes of proteins involved in metabolism of nutrients could play significant roles in the extent of the effects of nutrition in the development of CC. The effect of dietary proteins greatly depends on the polymorphisms in the metabolising genes of these substances. Gene polymorphisms may have a role in colorectal cancer risk, especially in people with high meat intake, and this leads to a difference in the effects of meat consumption in different individuals. To conclude, dietary recommendations for the prevention and control of CC should be modified based on the genotype of different individuals. Increasing our knowledge on this field of nutritional genomics can lead to personalised preventive and therapeutic recommendations for CC patients.

DNA repair is an important signaling mechanism that is necessary to maintain genomic stability. Various types of DNA repair proteins are involved in the repair of different types of DNA damage. However, most of the DNA repair proteins are modified post-translation in order to activate their repair function, such as, ubiquitination, phosphorylation, acetylation, etc. Similarly, DNA repair proteins are also regulated by posttranscriptional modifications. Non-coding microRNAs (miRNAs) induced posttranscriptional regulation of mRNAs has gained attention in recent years. MiRNA-induced regulation of DNA repair proteins is of great interest, owing to its potential role in cancer therapy. In this review, we have summarized the role of different miRNAs in the regulation of various types of DNA repair proteins, which are essential for the maintenance of genomic stability.

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Repair of DNA-targeted anticancer agents is an active area of investigation of both fundamental and clinical interest. However, most studies have focused on a small number of compounds limiting our understanding of both DNA repair and the DNA damage response. S23906 is an acronycine derivative that shows strong activity toward solid tumors in experimental models. S23906 forms bulky monofunctional DNA adducts in the minor groove which leads to destabilization of the double-stranded helix. We now report that S23906 induces formation of DNA double strand breaks that are processed through homologous recombination (HR) but not Non-Homologous End-Joining (NHEJ) repair. Interestingly, S23906 exposure was accompanied by a higher sensitivity of BRCA2-deficient cells compared to other HR deficient cell lines and by an S-phase accumulation in wild-type (wt), but not in BRCA2-deficient cells. Recently, we have shown that S23906-induced S phase arrest was mediated by the checkpoint kinase Chk1. However, its activated phosphorylated form is equally induced by S23906 in wt and BRCA2-deficient cells, likely indicating a role for BRCA2 downstream of Chk1. Accordingly, override of the S phase arrest by either 7-hydroxystaurosporine (UCN-01) or AZD7762 potentiates the cytotoxic activity of S23906 in wt, but not in BRCA2-deficient cells. Together, our findings suggest that the pronounced sensitivity of BRCA2-deficient cells to S23906 is due to both a defective S-phase arrest and the absence of HR repair. Tumors with deficiencies for proteins involved in HR, and BRCA2 in particular, may thus show increased sensitivity to S23906, thereby providing a rationale for patient selection in clinical trials.

BACKGROUND: High mobility group box1 (HMGB1) and poly(ADP-ribose) polymerase1 (PARP1) proteins repair cellular DNA damage. Reduced expression of the corresponding genes can lead to an impaired DNA damage repair mechanism. Intracellular replication of hepatitis B virus (HBV) in such conditions can favor the integration of viral DNA into host genome leading to the development of hepatocellular carcinoma (HCC).
OBJECTIVE: This study was performed to assess the expression of HMGB1 and PARP1 mRNAs in conjunction with the estimation of HBV replication intermediate pregenomic RNA (PgRNA) in various phases of HBV infection.
METHODS: Eighty eight patients and 26 voluntary blood donors as controls were included in the study. Patients were grouped in to acute (AHB; n = 15), inactive carriers (IC; n = 36), cirrhosis (Cirr; n = 25) and hepatocellular carcinoma (HCC; n = 12). Serum HBV DNA was quantified by real time polymerase chain reaction (PCR) assay. Expression of HMGB1, PARP1 and PgRNA were evaluated using peripheral blood mononuclear cells (PBMCs) derived RNA by reverse transcription PCR (RT-PCR) and densitometry.
RESULTS: Significant reduction of HMGB1 and PARP1 gene expressions (P < 0.05) were observed in patients than controls with more explicit decline of PARP1 (P = 0.0002). Both genes were significantly downregulated (P < 0.001) in ICs than controls. In ICs, HMGB1 was significantly lowered than cirrhosis (P = 0.002) and HCC (P = 0.0006) while PARP1 declined significantly (P = 0.04) than HCC. Level of PgRNA was comparable in all the disease categories.
CONCLUSIONS: In conclusion, our findings indicate impaired DNA damage repair mechanisms in HBV infected cells of ICs. This, along with low viral load but higher level of PgRNA in this group is suggestive of the diversion of HBV replication pathway that might facilitate viral DNA integration in to host genome. Intrusion of HBV PgRNA reverse transcription in early stage of infection might appear advantageous to thwart the development of HCC.