RUNX2 is a transcription factor playing the major role in osteogenesis, but it can be involved in DNA damage response, which is crucial for cancer transformation. RUNX2 can interact with cell cycle regulators: cyclin-dependent kinases, pRB and p21Cip1 proteins, as well as the master regulator of the cell cycle, the p53 tumor suppressor. RUNX2 is involved in many signaling pathways, including those important for estrogen signaling, which, in turn, are significant for breast carcinogenesis. RUNX2 can promote breast cancer development through Wnt and Tgfβ signaling pathways, especially in estrogen receptor (ER)-negative cases. ERα interacts directly with RUNX2 and regulates its activity. Moreover, the ERα gene has a RUNX2 binding site within its promoter. RUNX2 stimulates the expression of aromatase, an estrogen producing enzyme, increasing the level of estrogens, which in turn stimulate cell proliferation and replication errors, which can be turned into carcinogenic mutations. Exploring the role of RUNX2 in the pathogenesis of breast cancer can lead to revealing new therapeutic targets.

RUNX2 is a member of the RUNX family of transcription factors, also containing the RUNX1 and RUNX3 proteins. These factors control the expression of genes essential for proper development in many cell lineages. RUNX2 plays a crucial role in the proliferation and differentiation of osteoblasts, required for bone formation. The cellular level of RUNX2 oscillates in a cell phase-specific manner, reaching a maximum at G2/M in some cells and overexpression of RUNX2 in osteoblasts blocked G1 to S phase progression. Recent studies have shown that RUNX2 may interact with p53 and change the activity of a histone deacetylase. Moreover, RUNX2 may act as an oncogene in cancer transformation, inevitably associated with genomic instability evoked by increased occurrence of DNA damage. We showed that some RUNX2 modifiers changed the sensitivity of differentiating preosteoblasts to DNA damage induced by oxidative stress. All these data suggest the involvement of RUNX2 in cellular DNA damage response (DDR), which is particularly important in osteogenesis as the process of osteoblast differentiation is associated with increasing oxidative stress. However, the mechanism underlying DDR involvement of RUNX2 is unknown. The basic question, whether RUNX2 plays a positive or destructive role in DDR in differentiating cells is still open.

In this study, we compared the effect of tricarbonyldichlororuthenium (II) dimer (CORM-2) and its CO-depleted molecule (iCORM-2) on human peripheral blood mononuclear cells (PBMCs) and human promyelocytic leukemia HL-60 cells. We determined cell viability, DNA damage and DNA repair kinetics. We also studied the effect of both compounds on DNA oxidative damage, free radical level and HO-1 gene expression. We showed that at low concentrations both CORM-2 and iCORM-2 stimulate PBMCs viability. After 24-h incubation, CORM-2 and iCORM-2, at the concentration of 100 µM, reduce the viability of both PBMCs and HL-60 cells. We also demonstrated that CORM-2 and iCORM-2, in the 0.01-100 µM concentration range, cause DNA damage such as strand breaks and alkaline labile sites. DNA damage was repaired efficiently only in HL-60 cells. CORM-2 significantly reduces oxidative stress induced by 1 mM H 2 o 2 in normal and cancer cells. On the contrary, iCORM-2 in HL-60 cells increases the level of free radicals in the presence of 1 and 5 mM H 2 o 2. We also revealed that both CORM-2 and iCORM-2 induce HO-1 gene expression. However, CORM-2 induces this gene to a greater extent than iCORM-2, especially in HL-60 cells at 100 µM. Finally, we showed that CORM-2 and iCORM-2 reduce H 2 o 2-induced DNA oxidative damage. Furthermore, CORM-2 proved to be a compound with stronger antioxidant properties than iCORM-2. Our results suggest that both active CORM-2 and inactive iCORM-2 exert biological effects such as cyto-and genotoxicity, antioxidant properties and the ability to induce the HO-1 gene. The released CO as well as iCORM-2 can be responsible for these effects. Carbon monoxide (CO) is a colorless, tasteless and odorless gas produced by the burning of fuels and organic materials. It is reported to be the most frequent cause of fatal poisoning with an incidence rate of 31%. CO is readily absorbed and is unchanged by the lungs. CO demonstrates more than 200-fold stronger affinity for hemoglobin compared to oxygen. Therefore, even a small level of CO may cause poisoning. In contrast to hypoxiainducing toxic concentrations, a low dose of CO or even nanomolar concentrations exert biological activities. CO is produced in low amounts as a byproduct of normal human metabolism by the enzyme called heme oxygenase (HO-1) 1. CO has the ability to reduce the stimulation of guanylate cyclase to generate cyclic guanosine 3′,5′-monophosphate (cGMP). As a signaling molecule, CO modulates several p38 mitogen-activated protein kinase (MAPK)-related signaling pathways via both cGMP-dependent and independent processes, directly activates calcium-dependent potassium channels and induces protein kinase B (Akt) phosphorylation via the phosphatidylinositol 3-kinase/Akt pathway 2. Moreover, CO inhibits mitochondrial respiration by binding the ferrous heme a 3 in the active site of cyclooxygenase (COX), effectively shutting down oxidative phosphorylation, similar to the effects of cyanide and nitric oxide (NO) 3. The cGMP-dependent activity of CO includes inhibit...

Bisphenol A-glycidyl methacrylate (BisGMA) is monomer of dental filling composites, which can be released from these materials and cause adverse biologic effects in human cells. In the present work, we investigated genotoxic effect of BisGMA on human lymphocytes and human acute lymphoblastic leukemia cell line (CCRF-CEM) cells. Our results indicate that BisGMA is genotoxic for human lymphocytes. The compound induced DNA damage evaluated by the alkaline, neutral, and pH 12.1 version of the comet assay. This damage included oxidative modifications of the DNA bases, as checked by DNA repair enzymes EndoIII and Fpg, alkali-labile sites and DNA double-strand breaks. BisGMA induced DNA-strand breaks in the isolated plasmid. Lymphocytes incubated with BisGMA at 1 mM were able to remove about 50% of DNA damage during 120-min repair incubation. The monomer at 1 mM evoked a delay of the cell cycle in the S phase in CCRF-CEM cells. The experiment with spin trap—DMPO demonstrated that BisGMA induced reactive oxygen species, which were able to damage DNA. BisGMA is able to induce a broad spectrum of DNA damage including severe DNA double-strand breaks, which can be responsible for a delay of the cell cycle in the S phase.

Bioactive compounds isolated from plants are considered to be attractive candidates for cancer therapy. In this study, we examined the effect of kaempferol, its derivatives, the polyphenol fraction (PF) and an extract (EX) isolated from the aerial parts of Lens culinaris Medik. on DNA damage induced by etoposide in human cells. We also studied the effect of these compounds and their combinations on cell viability. The studies were conducted on HL-60 cells and human peripheral blood mononuclear cells (PBMCs). We used the comet assay in the alkaline version to evaluate DNA damage. To examine cell viability we applied the trypan blue exclusion assay. We demonstrated that kaempferol glycoside derivatives isolated from the aerial parts of Lens culinaris Medik. reduce DNA damage induced by etoposide in PBMCs, but do not have an impact on DNA damage in HL-60 cells. We also showed that kaempferol induces DNA damage in HL-60 cells and leads to an increase of DNA damage provoked by etoposide. Our data suggest that kaempferol derivatives can be further explored as a potential agent protecting normal cells against DNA damage induced by etoposide. Moreover, kaempferol's ability to induce DNA damage in cancer cells and to increase DNA damage caused by etoposide may be useful in designing and improving anticancer therapies.