Single nucleotide polymorphisms in DKK3 gene are associated with prostate cancer risk and progression

lnc‑MICAL2‑1 sponges miR‑25 to regulate DKK3 expression and inhibits activation of the Wnt/β‑catenin signaling pathway in breast cancer

The Dickkopf 3 (DKK3) protein antagonizes the Wnt receptor complex in the Wnt signaling pathway; however, to date, there have been no relevant studies investigating its upstream regulatory mechanism in breast cancer (BC), to the best of our knowledge. The present study aimed to explore whether long non‑coding RNA MICAL2‑1 (lnc‑MICAL2‑1) sponged microRNA (miR)‑25 to regulate DKK3 and inhibit activation of the Wnt/β‑catenin signaling pathway. The Atlas of non‑coding RNA in Cancer database was used to measure the expression levels of lnc‑MICAL2‑1 and their correlation with DKK3 expression levels. In addition, cell proliferation, invasion and migration were determined following the silencing or overexpression of lnc‑MICAL2‑1. The binding between lnc‑MICAL2‑1 and miR‑25, or miR‑25 and DKK3 was verified using RNA pull‑down and dual‑luciferase reporter assays. The effects of overexpression or knockdown of lnc‑MICAL2‑1 on DKK3 expression and the Wnt signaling pathway were further evaluated in a nude mouse xenograft model. The results revealed that, compared with in adjacent normal tissue, the expression levels of lnc‑MICAL2‑1 were downregulated in BC tissues, and the expression levels of lnc‑MICAL2‑1 were found to be positively correlated with DKK3 expression. The overexpression of lnc‑MICAL2‑1 in BC cells upregulated the mRNA expression levels of DKK3 and inhibited their proliferation. Results from the RNA pull‑down and dual luciferase reporter assays validated that lnc‑MICAL2‑1 could bind to miR‑25, which targets DKK3. The in vivo experimental data demonstrated that lnc‑MICAL2‑1 inhibited tumor growth via regulating the Wnt signaling pathway. In conclusion, the findings of the present study highlighted a novel molecular mechanism through which lnc‑MICAL2‑1 may regulate the DKK3‑mediated Wnt signaling pathway in BC, highlighting potential targets for the treatment of the disease.

Dihydrotestosterone inhibits arylsulfatase B and Dickkopf Wnt signaling pathway inhibitor (DKK)-3 leading to enhanced Wnt signaling in prostate epithelium in response to stromal Wnt3A

BACKGROUND

In tissue microarrays, immunostaining of the enzyme arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase) was less in recurrent prostate cancers and in cancers with higher Gleason scores. In cultured prostate stem cells, decline in ARSB increased Wnt signaling through effects on Dickkopf Wnt Signaling Pathway Inhibitor (DKK)3. The effects of androgen exposure on ARSB and the impact of decline in ARSB on Wnt signaling in prostate tissue were unknown.

METHODS

Epithelial and stromal tissues from malignant and normal human prostate were obtained by laser capture microdissection. mRNA expression of ARSB, galactose-6-sulfate-sulfatase (GALNS) and Wnt-signaling targets was determined by QPCR. Non-malignant human epithelial and stromal prostate cells were grown in tissue culture, including two-cell layer cultures. ARSB was silenced by specific siRNA, and epithelial cells were treated with stromal spent media following treatment with IWP-2, an inhibitor of Wnt secretion, and by exogenous recombinant human Wnt3A. Promoter methylation was detected using specific DKK3 and ARSB promoter primers. The effects of DHT and of ARSB overexpression on DKK expression were determined. Cell proliferation was assessed by BrdU incorporation.

RESULTS

Normal stroma showed higher expression of vimentin, ARSB, and Wnt3A than epithelium. Normal epithelium had higher expression of E-cadherin, galactose 6-sulfate-sulfatase (GALNS), and DKK3 than stroma. In malignant epithelium, expression of ARSB and DKK3 declined, and expression of GALNS and Wnt signaling targets increased. In cultured prostate epithelial cells, Wnt-mediated signaling was greatest when ARSB was silenced and cells were exposed to exogenous Wnt3A. Exposure to 5α-dihydrotestosterone (DHT) increased ARSB and DKK3 promoter rmethylation, and effects of DHT on DKK3 expression were reversed when ARSB was overexpressed.

CONCLUSIONS

Androgen-induced declines in ARSB and DKK3 may contribute to prostate carcinogenesis by sustained activation of Wnt signaling in prostate epithelium in response to stromal Wnt3A.

Dickkopf homolog 3 (DKK3): A candidate for detection and treatment of cancers?

Wnt signaling is an evolutionary highly conserved pathway that is modulated by several inhibitors and activators, and plays a key role in numerous physiological processes. One of the extracellular Wnt inhibitors is the DKK (Dickkopf Homolog) family which has four members (Dkk1-4) and a unique Dkk3-related gene, Dkkl1 (soggy). DKK3 is a divergent member of the DKK protein family. Evidence suggests that DKK3 may serve as a potential therapeutic target in several types of human cancers. We review here the biological role of DKK3 as a tumor suppressor gene (TSG) or oncogene, and its correlation with various miRNAs. In addition, we discuss the role of polymorphisms and promoter methylation of the DKK3 gene, and of its expression in regulating cancer cell proliferation. Finally, we propose that DKK3 may be considered as both a biomarker and a therapeutic target in different cancers.

High-order gene interactions between the genetic polymorphisms in Wnt and AhR pathway in modulating lung cancer susceptibility

AIM

Genetic variations present within Wnt and AhR pathway might be related to the lung cancer susceptibility.

METHODS

A total of 555 subjects were genotyped using PCR-RFLP technique for polymorphic sites in DKK4, DKK3, DKK2, sFRP3, sFRP4, Axin2 and AhR. Multifactor dimensionality reduction method and classification and regression tree analysis was used.

RESULTS

Overall sFRP4_rs1802073 which has a cross validation consistency of 10/10, prediction error = 0.43 (p > 0.0001) is the best factor model. The second best model was sFRP4_rs1802073 and DKK2_rs419558 with cross validation consistency of 9/10 and prediction error = 0.40. In classification and regression tree analysis, DKK2 _rs419558 came out to be a significant factor; DKK2_rs17037102 (M)/DKK2_rs419558 (M) showed a tenfold risk of acquiring lung cancer, p = 0.0001. DKK2_rs17037102 (M)/AhR_rs2066853 (W)/AhR_rs10250822 (M) showed an 11-fold risk of developing lung cancer, p = 0.00001.

CONCLUSION

Both DKK2 and sFRP4 polymorphisms are found to play a crucial role; especially for smokers towards modulating risk for lung cancer. AhR variants are contributing maximally toward lung cancer risk.

Association of polymorphisms in Dickopff (DKK) gene towards modulating risk for lung cancer in north Indians

AIM

To investigate the association between the genetic variants of DKK4 (rs2073664), DKK3 (rs2291599, rs3206824 and rs7391689) and DKK2 (rs447372, rs419558 and rs17037102) and lung cancer predisposition in north Indians.

MATERIALS & METHODS

A total of 600 subjects were genotyped using PCR restriction fragment length polymorphism technique. Association analysis was carried out using logistic regression approach.

RESULTS

DKK3 rs7396187 showed a protective effect (p = 0.01). Subjects with heterozygous genotype of DKK2 rs17037102 and rs419558 showed an increased risk. The variant genotype of the genotypic combination, DKK3 rs3206824 and DKK2 rs419558 showed a twofold increased risk (p = 0.008). Lung cancer risk increased four-times in subjects with variant genotype of all the three DKK2 variants.

CONCLUSION

DKK2 is certainly playing a crucial role in modulating cancer susceptibility.