Short-term detection of gastric genotoxicity using the DNA double-strand break marker γ-H2AX

Early detection of urinary bladder carcinogens in rats by immunohistochemistry for γ-H2AX: a review from analyses of 100 chemicals

In safety evaluations of chemicals, there is an urgent need to develop short-term methods to replace long-term carcinogenicity tests. We have reported that immunohistochemistry for γ-H2AX, a well-established biomarker of DNA damage, can detect bladder carcinogens at an early stage using histopathological specimens from 28-day repeated-dose oral toxicity studies in rats. Given the markedly low level of γ-H2AX formation in the bladder urothelium of untreated rats, an increase in γ-H2AX-positive cells following chemical exposure can be relatively easy to identify. Among the 100 compounds examined to date, bladder carcinogens can be detected with high sensitivity (33/39; 84.6%) and specificity (58/61; 95.1%). As expected, γ-H2AX formation levels tended to be high following exposure to genotoxic bladder carcinogens, whereas nongenotoxic bladder carcinogens also increased the number of γ-H2AX-positive cells, probably through secondary DNA damage associated with sustained proliferative stimulation. γ-H2AX formation in the bladder urothelium reflects species differences in susceptibility to bladder carcinogenesis between rats and mice and shows a clear dose-dependency associated with the intensity of tumor development as well as high reproducibility. Some of the bladder carcinogens that showed false-negative results in the evaluation of γ-H2AX alone could be detected by combined evaluation with immunostaining for bladder stem cell markers, including aldehyde dehydrogenase 1A1. This method may be useful for the early detection of bladder carcinogens, as it can be performed by simple addition of conventional immunostaining using formalin-fixed paraffin-embedded tissues from 28-day repeated-dose toxicity studies in rodents, which are commonly used in safety evaluations of chemical substances.

GDF10 inhibits proliferation and epithelial-mesenchymal transition in triple-negative breast cancer via upregulation of Smad7

Triple-negative breast cancer (TNBC) cannot be treated with current hormonal therapies and has a higher risk of relapse than other breast cancers. To identify potential therapeutic targets for TNBC, we conducted microRNA sequencing (RNA-Seq) in human TNBC specimens and tumor-matched controls. We found that growth differentiation factor-10 (GDF10), a member of the TGF-β superfamily, was downregulated in tumor samples. Further analysis of GDF10 expression in a larger set of clinical TNBC samples using qPCR confirmed its downregulation and association with parameters of disease severity. Using human-derived TNBC cell lines, we carried out GDF10 under- and overexpression experiments, which showed that GDF10 loss promoted cell proliferation and invasion. By contrast, overexpression of GDF10 inhibited proliferation, invasion, and epithelial mesenchymal transition (EMT) via upregulation of Smad7 and E-Cadherin, downregulation of p-Smad2 and N-Cadherin, and reduction of nuclear Smad4 expression. In addition, overexpression of GDF10 reduced tumor burden and induced apoptosis in a TNBC xenograft mouse model. These findings indicate that GDF10 acts as a tumor suppressor in mammary epithelial cells that limits proliferation and suppresses EMT. Efforts aimed at restoring GDF10 expression may thus bring a long-sought therapeutic alternative in the treatment of patients with TNBC.

Overexpression of SNORA21 suppresses tumorgenesis of gallbladder cancer in vitro and in vivo

BACKGROUND

Gallbladder cancer (GBC) ranks fifth in the most common malignancy of the gastrointestinal tract worldwide. It is reported many small nucleolar RNAs (SNORNs) could regulate the progression of GBC. To identify potential therapeutic targets for GBC, we conducted microarray analysis in GBC tissues and adjacent normal tissues. We found that SNORA21 was downregulated most in gallbladder tumor samples. Therefore, this research aimed to investigate the role of SNORA21 during the tumorigenesis of GBC.

METHODS

The differential expression of SNORNs between GBC tissues and para-carcinoma tissues were examined by microarray analysis and that were confirmed by qRT-PCR. Cell proliferation was tested by CCK-8 and immunofluorescence. Cell apoptosis and cell cycle in GBC were detected by flow cytometry. Expression of proteins in GBC cells was measured by Western-blot. Transwell assay was used for testing the cell migration and invasion. Xenograft tumor model was established to verify the effect of SNORA21 overexpression on GBC in vivo.

RESULTS

The results revealed that SNORA21 overexpression inhibited the proliferation, migration and invasion of GBC cells. Moreover, overexpression of SNORA21 significantly increased the expression of E-cadherin and decreased the levels of N-cadherin and vimentin. Meanwhile, overexpression of SNORA21 significantly induced apoptosis and G1 arrest of GBC cells. Finally, SNORA21 overexpression significantly suppressed the growth of gallbladder tumors in vivo.

CONCLUSION

Overexpression of SNORA21 significantly suppressed the tumorigenesis of GBC in vitro and in vivo, which may serve as a potential novel target for the treatment of GBC.