The non-vesicle cell-free DNA (cfDNA) induces cell transformation associated with horizontal DNA transfer.

BACKGROUND: Cell-free DNA (cfDNA) is a source for liquid biopsy used for cancer diagnosis, therapy selection, and disease monitoring due to its non-invasive nature and ease of extraction. However, cfDNA also participates in cancer development and progression by horizontal transfer. In humans, cfDNA circulates complexed with extracellular vesicles (EV) and macromolecular complexes such as nucleosomes, lipids, and serum proteins. The present study aimed to demonstrate whether cfDNA not associated with EV induces cell transformation and tumorigenesis. METHODS: Supernatant of the SW480 human colon cancer cell line was processed by ultracentrifugation to obtain a soluble fraction (SF) and a fraction associated with EV (EVF). Primary murine embryonic fibroblast cells (NIH3T3) underwent passive transfection with these fractions, and cell proliferation, cell cycle, apoptosis, cell transformation, and tumorigenic assays were performed. Next, cfDNA was analyzed by electronic microscopy, and horizontal transfer was assessed by human mutant KRAS in recipient cells via PCR and recipient cell internalization via fluorescence microscopy. RESULTS: The results showed that the SF but not the EVF of cfDNA induced proliferative and antiapoptotic effects, cell transformation, and tumorigenesis in nude mice, which were reduced by digestion with DNAse I and proteinase K. These effects were associated with horizontal DNA transfer and cfDNA internalization into recipient cells. CONCLUSIONS: The results suggest pro-tumorigenic effects of cfDNA in the SF that can be offset by enzyme treatment. Further exploration of the horizontal tumor progression phenomenon mediated by cfDNA is needed to determine whether its manipulation may play a role in cancer therapy.

Hereditary diffuse gastric cancer (HDGC). An overview.

It is estimated that up to 10% of gastric carcinomas show familial aggregation. In contrast, around 1-3 % (approximately 33,000 yearly) are genuinely hereditary. Hereditary diffuse gastric cancer (HDGC) is a rare malignancy characterized by autosomal dominant inheritance of pathological variants of the CDH1 and CTNNA1 genes encoding the adhesion molecules E-cadherin and α-catenin, respectively. The multifocal nature of the disease and the difficulty of visualizing precursor lesions by endoscopy underscore the need to be aware of this malignancy as surgical prevention can be fully protective. Here, we provide an overview of the main epidemiological, clinical, genetic, and pathological features of HDGC, as well as updated guidelines for its diagnosis, genetic testing, counseling, surveillance, and management. We conclude that HDGC is a rare, highly penetrant disease that is difficult to diagnose and manage, so it is necessary to correctly identify it to offer patients and their families' adequate management following the recommendations of the IGCL. A critical point is identifying a mutation in HDGC families to determine whether unaffected relatives are at risk for cancer.

Nicotinamide sensitizes human breast cancer cells to the cytotoxic effects of radiation and cisplatin.

Poly(ADP-ribose) polymerase (PARP) inhibitors enhance the effect of DNA alkylating agents on BRCA1­ and BRCA2-deficient cell lines. The aim of this study was to analyze the effect of the PARP inhibitor nicotinamide (NAM) on breast cancer cells with different BRCA1 expression or function, such as BRCA1­deficient MDA-MB-436 cells, low expression BRCA1 MCF-7 cells, and the BRCA1 wild­type MDA-MB-231 cells, to demonstrate its effects as a chemo­ or radiosensitizing agent. PARP activity was analyzed in MDA-MB-436, MCF-7 and MDA-MB-231 breast cancer cells subjected or not to NAM. Inhibition of PARP by NAM in the presence of DNA damage was examined by Alexa Fluor 488 immunofluorescence. Crystal violet assays were used to test growth inhibition and the chemo­ and radiosensitization effects of NAM were investigated using clonogenic assays. Significant differences among data sets were determined using two-tailed ANOVA and Bonferroni tests. We demonstrated that NAM reduces PARP activity in vitro, and in cells subjected or not to DNA damage, it also reduces the viability of breast cancer cell lines and synergyzes the cytotoxicity of cisplatin in MDA-MB-436 and MCF-7 cells. Downregulation of PARP1 with siRNA led to modest growth inhibition, which was further increased by cisplatin. Nicotinamide also induced radiosensitization in MDA-MB-436 and MDA-MB-231 cells. In conclusion, NAM may be used as a chemo­ or radiosensitizing agent regardless of the BRCA1 status in breast cancer.