Elevated levels of extrachromosomal circular DNA (eccDNA or spcDNA) are closely associated with genomic instability and aging. Despite extensive studies, the mechanism of its generation in mammalian cells is unknown. We report here that mouse major satellite DNA (MSD) is prone to eccDNA formation and that the resulting molecules are multimeres of the basic repeat. Extrachromosomal circular major satellite (ECMS) DNA constitutes the majority of eccDNA in B16 mouse melanoma cells and is highly abundant in other mouse cells. Production of these molecules is enhanced in proliferating cells, suggesting that processes associated with DNA replication are involved in their appearance. Using siRNA technique we show that DNA Ligase IV is engaged in ECMS synthesis. Based on our findings we propose a novel two-step model for eccDNA formation in mammalian cells.

Extrachromosomal circular DNA (eccDNA) is a pool of circular double stranded DNA molecules found in all eukaryotic cells and composed of repeated chromosomal sequences. It was proposed to be involved in genomic instability, aging and alternative telomere lengthening. Our study presents novel mammalian cell-free system for eccDNA generation. Using purified protein extract we show that eccDNA formation does not involve de-novo DNA synthesis suggesting that eccDNA is generated through excision of chromosomal sequences. This process is carried out by sequence- independent enzymes as human protein extract can produce mouse- specific eccDNA from high molecular weight mouse DNA, and vice versa. EccDNA production does not depend on ATP, requires residual amounts of Mg2+ and is enhanced by double strand DNA breaks.

Numerous botanicals have been shown to exhibit in vitro and in vivo anticancer activity, some of which is the result of the induction of reactive oxygen species (ROS) in cancer cells with a high ROS content. The present study compared sensitivities to a series of botanicals among cancer cell lines, using an XTT viability test, in order to create a specific cancer-herb profile. Of the 27 botanicals screened, 10 exhibited a cytotoxic effect, 7 of which were ROS-mediated. The sensitivity profiles of the ROS-inducing botanicals in 10 cancer cell lines were similar, unlike 3 cytotoxic ROS-independent botanicals that displayed divergent botanical-specific profiles. The correlation between sensitivity profiles of ROS-inducing botanicals suggests a common mechanism of action, in contrast to the varied mechanism of ROS-independent botanicals. This implies that the investigation of the anticancer activity of botanicals should start with the examination of ROS-mediated activity. Further investigation of ROS sensitivity among various tumor types is required in order to guide research into developing evidence-based guidelines in the use of botanicals for cancer treatment.

There is a need for new options for reducing the side effects of cancer treatment, without compromising efficacy, enabling patients to complete treatment regimens. The botanical compound LCS101 exhibits inhibitory effects on cancer cell growth, and reduces chemotherapy-induced hematological toxicities. The aim of the present study is to examine the selectivity of the effects of the compound, alone and in conjunction with conventional chemotherapy agents, on cancer cell proliferation. The effects of LCS101 were tested on a number of cancer cell lines (breast, MCF7, MDA-MB‑231; colorectal, HCT116; prostate, PC-3, DU-145) and on non-tumorigenic normal human epithelial cells (breast, MCF10A; prostate, EP#2). Cell viability was analyzed using an XTT assay and observed by light microscopy. Necrosis and apoptosis were examined using FACS analysis and immunoblotting. LCS101 selectively induced cell death in breast, colon and prostate cancer cell lines, as measured by XTT assay. Light microscopy and FACS analysis showed changes indicative of a necrotic process. LCS101 was also found to induce PARP-1 reduction in breast cancer cells, with no effect on non-tumorigenic breast epithelial cells. While LCS101 increased cell death in cancer cells exposed to doxorubicin and 5-FU, it showed a protective effect on non-tumorigenic human epithelial cells from chemotherapy-induced cell death. A similar selective effect was observed with apoptosis-associated PARP-1 cleavage. The findings demonstrate that the anti-proliferative effects exhibited by the botanical compound LCS101 are selective to cancer cells, and offer protection to non-tumorigenic normal epithelial cells from chemotherapy agents.

The insulin-like growth factor-1 receptor (IGF1R) emerged in recent years as a promising therapeutic target in oncology. Identification of potential biomarkers capable of predicting response to IGF1R-targeted therapy is of cardinal importance. Tumor suppressor BRCA1 has important roles in multiple pathways, including gene transcription, DNA damage repair, and control of apoptosis. Early studies have identified the IGF1R gene as a downstream target for inhibitory regulation by wild-type, but not mutant, BRCA1. The aim of the present study was to evaluate the hypothesis that the mutational status of BRCA1 may influence the ability of IGF1R-directed therapies to efficiently inhibit the IGF1R axis. Using breast cancer-derived cell lines expressing a wild-type or a mutant BRCA1, we demonstrate that the capacity of MK-0646, a monoclonal antibody antagonist to the human IGF1R, to inhibit insulin-like growth factor-1-stimulated IGF1R and downstream mediators’ phosphorylation was impaired in mutant BRCA1-expressing cell lines. In addition, the antibody was able to reduce proliferation of wild-type BRCA1-expressing cells but had a reduced inhibitory effect in mutant BRCA1-expressing cells. In summary, our data indicate that the mutational status of BRCA1 must be taken into account when selecting patients for IGF1R targeting protocols.