Mammalian cells are frequently at risk of DNA damage from both endogenous and exogenous sources. Accordingly, cells have evolved the DNA damage response (DDR) pathways to monitor and assure the integrity of their genome. In cells, the intact and effective DDR is essential for the maintenance of genomic stability and it acts as a critical barrier to suppress the development of cancer in humans. Two central kinases for the DDR pathway are ATM and ATR, which can phosphorylate and activate many downstream proteins for cell cycle arrest, DNA repair, or apoptosis if the damages are irreparable. In the last several years, we and others have made significant progress to this field by identifying BRIT1 (also known as MCPH1) as a novel key regulator in the DDR pathway. BRIT1 protein contains 3 breast cancer carboxyl terminal (BRCT) domains which are conserved in BRCA1, MDC1, 53BP1, and other important molecules involved in DNA damage signaling, DNA repair, and tumor suppression. Our in vitro studies revealed BRIT1 to be a chromatin-binding protein required for recruitment of many important DDR proteins (ATM, MDC1, NBS1, RAD51, BRCA2) to the DNA damage sites. We recently also generated the BRIT1 knockout mice and demonstrated its essential roles in homologous recombination DNA repair and in maintaining genomic stability in vivo. In humans, BRIT1 is located on chromosome 8p23.1, where loss of hetero-zigosity is very common in many types of cancer. In this review, we will summarize the novel roles of BRIT1 in DDR, describe the relationship of BRIT1 deficiency with cancer development, and also discuss the use of synthetic lethality approach to target cancers with HR defects due to BRIT1 deficiency.
Animals ; Chromosomal Proteins, Non-Histone/genetics/metabolism/*physiology ; DNA Damage/genetics/*physiology ; DNA Repair/genetics/*physiology ; Humans ; Mice ; Models, Biological ; Neoplasms/*genetics ; Nerve Tissue Proteins/genetics/metabolism/*physiology

Mammalian cells are frequently at risk of DNA damage from both endogenous and exogenous sources. Accordingly, cells have evolved the DNA damage response (DDR) pathways to monitor and assure the integrity of their genome. In cells, the intact and effective DDR is essential for the maintenance of genomic stability and it acts as a critical barrier to suppress the development of cancer in humans. Two central kinases for the DDR pathway are ATM and ATR, which can phosphorylate and activate many downstream proteins for cell cycle arrest, DNA repair, or apoptosis if the damages are irreparable. In the last several years, we and others have made significant progress to this field by identifying BRIT1 (also known as MCPH1) as a novel key regulator in the DDR pathway. BRIT1 protein contains 3 breast cancer carboxyl terminal (BRCT) domains which are conserved in BRCA1, MDC1, 53BP1, and other important molecules involved in DNA damage signaling, DNA repair, and tumor suppression. Our in vitro studies revealed BRIT1 to be a chromatin-binding protein required for recruitment of many important DDR proteins (ATM, MDC1, NBS1, RAD51, BRCA2) to the DNA damage sites. We recently also generated the BRIT1 knockout mice and demonstrated its essential roles in homologous recombination DNA repair and in maintaining genomic stability in vivo. In humans, BRIT1 is located on chromosome 8p23.1, where loss of hetero-zigosity is very common in many types of cancer. In this review, we will summarize the novel roles of BRIT1 in DDR, describe the relationship of BRIT1 deficiency with cancer development, and also discuss the use of synthetic lethality approach to target cancers with HR defects due to BRIT1 deficiency.
Animals ; Chromosomal Proteins, Non-Histone/genetics/metabolism/*physiology ; DNA Damage/genetics/*physiology ; DNA Repair/genetics/*physiology ; Humans ; Mice ; Models, Biological ; Neoplasms/*genetics ; Nerve Tissue Proteins/genetics/metabolism/*physiology

Animals ; Autoantigens ; genetics ; metabolism ; physiology ; Centromere Protein A ; Chromosomal Instability ; Chromosomal Proteins, Non-Histone ; genetics ; metabolism ; physiology ; Gene Expression Regulation, Neoplastic ; Humans ; Kinetochores ; metabolism ; Mitosis ; physiology ; Rectal Neoplasms ; genetics ; metabolism ; pathology ; Spindle Apparatus ; metabolism

BACKGROUNDIntegrase interactor 1 (INI1), which encodes a component of the ATP-dependent chromatin remodeling hSWI-SNF complex, has been identified as a tumor suppressor in many tumors. Nonetheless, the role of INI1 in gastric tumor progression is not known exactly. The aim of this research was to investigate the effect of INI1 in the carcinogenesis and progression of gastric cancer.

METHODSGastric tumor tissues with different differentiation levels from clinical gastric carcinoma samples and adjacent control normal tissues were taken. Expression levels of INI1 were detected by quantitative reverse transcriptation-polymerase chain reaction (RT-PCR) and Western blotting. Gastric cancer cell line SGC7901 was transfected with INI1 eukaryotic expressing vector INI1-GFP. Cell proliferation activities were assessed by MTT; cell count and cell cycle were detected by flow cytometry (FCM); cell apoptosis were measured by TUNEL and FCM; cell migration and invasiveness were evaluated by wound healing and transwell assays. Expression levels of INI1 and proliferation-related genes including p16, p21, cyclin D1 and cyclin A, apoptosis genes p53, B-cell non-Hodgkin lymphoma-2 (Bcl-2), Bcl-2-associated x protein (Bax) and caspase-3, and invasion-related genes including intercellular adhesion molecule 1 (ICAM1), matrix metalloproteinase 2 (MMP2), MMP9 and tissue inhibitor of matrix metalloproteinase 1 (TIMP1), were detected by quantitative RT-PCR and Western blotting.

RESULTSINI1 expression levels were lower in gastric carcinoma compared with adjacent control normal tissues. Overexpression of INI1 in SGC7901 cells inhibited its proliferation and invasiveness, but increased anoikis and G(0)/G(1) cell number. INI1-GFP transfection upregulated expression of INI1 and proliferation related genes p16 and p21, apoptosis genes p53 and Bax, and invasion-related genes TIMP1; cyclin D1, cyclin A, Bcl2, ICAM1, MMP2 and MMP9 were downregulated, and there was no significant change in caspase 3 levels.

CONCLUSIONINI1 plays a key role in gastric carcinogenesis by affecting proliferation, apoptosis and invasion.

Apoptosis ; genetics ; physiology ; Blotting, Western ; Cell Cycle ; genetics ; physiology ; Cell Line, Tumor ; Cell Proliferation ; Chromosomal Proteins, Non-Histone ; genetics ; metabolism ; DNA-Binding Proteins ; genetics ; metabolism ; Humans ; Real-Time Polymerase Chain Reaction ; SMARCB1 Protein ; Stomach Neoplasms ; genetics ; metabolism ; Transcription Factors ; genetics ; metabolism

OBJECTIVETo explore the correlation between expression of surviving gene in acute leukemic cells and its clinical effects.

METHODSBy using semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) technique, surviving gene expression in 50 previously untreated acute leukemia (AL) patients was analysed. The apoptosis of primary leukemia cells cultured in vitro was assayed with terminal deoxyribonucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL).

RESULTSSurviving gene expression levels in cells of AL patients at diagnosis were significantly higher than that in normal bone marrow mononuclear cells (MNCs) (82.0% vs 33.3%, P < 0.05). The expression level was higher in ALL cells than in ANLL cells (89.5% vs 75.0%). Among 22 cases of ANLL, bone marrow remission (BMR) rate was higher in surviving gene negative expression cells from patients accepted a course of chemotherapy than in positive expression cells (83.3% vs 25.0%, P = 0.023). Among 13 ANLL patients received a course of HA regimen chemotherapy, the BMR was higher in patients surviving mRNA negative expression cells than in positive cells (100.0% vs 27.3%). Patients with surviving/beta-actin ratio>0.6 attained lower BMR.

CONCLUSIONHigher expression level of surviving mRNA in AL cells may be one of the reasons that leukemic cells are insensitive to chemotherapy.

Adolescent ; Adult ; Aged ; Antineoplastic Agents ; therapeutic use ; Chromosomal Proteins, Non-Histone ; genetics ; metabolism ; Drug Resistance, Neoplasm ; genetics ; physiology ; Female ; Gene Expression Regulation, Leukemic ; Humans ; Inhibitor of Apoptosis Proteins ; Leukemia, Myeloid, Acute ; drug therapy ; genetics ; metabolism ; Male ; Microtubule-Associated Proteins ; Middle Aged ; Neoplasm Proteins ; Precursor Cell Lymphoblastic Leukemia-Lymphoma ; genetics ; metabolism ; RNA, Messenger ; biosynthesis ; Remission Induction ; Treatment Outcome