Detection of Cancer Marker Flap Endonuclease 1 Using One-Pot Transcription-Powered Clustered Regularly Interspaced Short Palindromic Repeat/Cas12a Signal Expansion.

As a critical functional protein in DNA replication and genome stability, flap endonuclease 1 (FEN1) has been considered a promising biomarker and druggable target for multiple cancers. We report here a transcription-powered clustered regularly interspaced short palindromic repeat (CRISPR)/Cas12a signal expansion platform for rapid and sensitive detection of FEN1. In this method, the probe cleavage by FEN1 generated a free 5' flap single-stranded DNA which could hybridize with the single-stranded T7 promoter-bearing template and trigger the extension. Then, the CRISPR guide RNA (crRNA) transcribed from the extended template activated the collateral DNase activity of Cas12a, releasing the fluorophore from the quenched DNA signal probe to report the FEN1 detection result. The high specificity for FEN1 was validated by comparing with other repair-relevant proteins. The limit of detection (LOD) could be as low as 0.03 mU, which is sensitive enough to detect the FEN1 activity in biological samples. In addition, the inhibition assay of FEN1 was also successfully achieved with this platform, proving its potential in inhibitor screening. In summary, this study provides a novel biosensor for FEN1 activity analysis and provides new insights into the development of CRISPR-based biosensors for non-nucleic acid targets.

Deubiquitylase OTUD6B stabilizes the mutated pVHL and suppresses cell migration in clear cell renal cell carcinoma.

Von Hippel-Lindau (VHL) is an important tumor suppressor, and its inactivation is a hallmark of inherited VHL disease and most sporadic clear cell renal cell carcinoma (ccRCC). VHL protein (pVHL) with missense point mutations are unstable and degraded by the proteasome because of the disruption of elongin binding. Deubiquitylase ovarian tumor domain-containing 6B (OTUD6B) had been documented to couple pVHL and elongin B to form stable VHL - elonginB - elonginC complex, which protects pVHL from degradation. However, whether OTUD6B governs the stability of pVHL wild type and the missense mutants in ccRCC remains largely elusive. Here, we reported that low OTUD6B level predicted poorer survival in ccRCC patients with VHL missense mutation, but not frameshift deletion and nonsense mutation. OTUD6B is able to interact with wild type pVHL and tumor-derived pVHL missense mutants, except for pVHL I151T, and decrease their ubiquitylation and proteasomal degradation in ccRCC cells. Functionally, we revealed that OTUD6B depletion enhanced cell migration and HIF-2α level in ccRCC cells in a pVHL dependent manner. In addition, OTUD6B depletion reduced the inhibitory effects of ectopic pVHL missense mutants on cell migration and HIF-2α level, except for pVHL I151T. Thus, we speculated that I151 residue might be one of key sites of pVHL binding to OTUD6B. These results suggested that OTUD6B is an important regulator for the stability of pVHL missense mutants, which provides a potential therapeutic strategy for ccRCC with VHL mutations.

[Correlation between serum anti-P53 and familial clustering of hepatocellular carcinoma in Guangxi].

OBJECTIVE: To assess the correlation between familial clustering of hepatocellular carcinoma (HCC) and the level of anti-P53 in human serum in Guangxi. METHODS: Enzyme-linked immunosorbent assay (ELISA) was used to detect anti-P53 in 164 members from 20 HCC families and 164 members from non-cancer control families. Univariate analysis was performed to assess the correlation between seral level of P53 antibody and familial clustering of HCC. RESULTS: The level of P53 antibody was significantly higher in the members of HCC families than controls (Z=-3.04, P=0.002). After eliminating the interference of hepatitis B virus infection, this tendency still remains (P=0.011). And there was a significant difference between relatives of different degrees from HCC families (chi-square=11.593, P=0.021), with the expression of anti-P53 declining along with decrease in relationship coefficient. Furthermore, the number of individuals with high anti-P53 expression was also significantly greater in HCC families (95/164) than controls (71/164) (P=0.006). And the expression was rising along with the increasing HCC numbers (chi-square=16.068, P=0.000). Anti-P53 level was also greater in HCC families featuring sibling affection than parental affection (chi-square=12.679, P=0.002). Univariate analysis indicated that high expression of anti-P53 is a risk factor for development of HCC (OR=2.087, 95%CI: 1.270-3.431). CONCLUSION: High level of anti-P53 expression may be a factor for the clustering of HCC families in Guangxi, China.