Fulvestrant is a selective estrogen receptor downregulator (SERD) and highly effective antagonist to hormone-sensitive breast cancers following failure of previous tamoxifen or aromatase inhibitor therapies. However, after prolonged fulvestrant therapy, acquired resistance eventually occurs in the majority of breast cancer patients, due to poorly understood mechanisms. To examine a possible role(s) of aberrantly expressed microRNAs (miRNAs) in acquired fulvestrant resistance, we compared antiestrogen-resistant and -sensitive breast cancer cells, revealing the over-expression of miR-221/222 in the SERD-resistant cell lines. Fulvestrant treatment of estradiol (E2)- and fulvestrant-sensitive MCF7 cells resulted in increased expression of endogenous miR-221/222. Ectopic upregulation of miR-221/222 in estrogen receptor-α (ERα)-positive cell lines counteracted the effects of E2 depletion or fulvestrant-induced cell death, thus also conferring hormone-independent growth and fulvestrant resistance. In cells with acquired resistance to fulvestrant, miR-221/222 expression was essential for cell growth and cell cycle progression. To identify possible miR-221/222 targets, miR-221- or miR-222- induced alterations in global gene expression profiles and target gene expression at distinct time points were determined, revealing that miR-221/222 overexpression resulted in deregulation of multiple oncogenic signaling pathways previously associated with drug resistance. Activation of β-catenin by miR-221/222 contributed to estrogen-independent growth and fulvestrant resistance, whereas TGF-β-mediated growth inhibition was repressed by the two miRNAs. This first in-depth investigation into the role of miR-221/222 in acquired fulvestrant resistance, a clinically important problem, demonstrates that these two ‘oncomirs’ may represent promising therapeutic targets for treating hormone-independent, SERD-resistant breast cancer.

Objective: The Grainyhead-like (GRHL) genes family were reported to participate in the development of a number of diseases. This study was designed to investigate the role of GRHL genes family in colon cancer (CC). Methods: In this study, the transcriptional levels of GRHL genes family in patients with CC from GEPIA were explored. Meanwhile, the immunohistochemical data of the GRHL genes family were also obtained in the HPA database. Additionally, we re-identified the mRNA of these genes via real-time PCR. Furthermore, the association between the levels of GRHL genes and stage plot as well as survival condition including overall survival and disease-free survival of patients with CC was analyzed. Finally, by transfecting with specific-siRNA, clone formation assay was performed to observe the role of GRHL genes family in the proliferation of SW480 human colon cancer cells. Results: We found that the mRNA and protein levels of GRHL1, GRHL2 and GRHL3 were significantly higher in CC tissues than in normal colon tissues. Additionally, GRHL1, GRHL2 and GRHL3 were significantly associated with the stages of CC. The Kaplan-Meier plotter showed that the low levels of GRHL1, GRHL2 and GRHL3 conferred a better overall survival of patients with CC while the high levels of GRHL1 and GRHL3 were associated with poor disease-free survival. Knockdown of GRHL1, GRHL2 and GRHL3 siHgnificantly inhibited the ability of colony formation of human colon cancer cells. Conclusion: Our study demonstrated that GRHL genes are involved in the prognosis and survival in patients with CC, the inhibition of which may suppress the proliferation of colon cancer cells.

Objective: Colon cancer (CC) is the third most common cancer with a high rate of incidence and mortality. Therefore, it is highly necessary to explore novel targets of CC. Methods: The miRNA-seq and RNA-seq data of CC were accessed from the TCGA database. Differential analysis was performed using the "edgeR" package to identify differentially expressed miRNAs (DE_miRNAs). The downstream target genes of the target miRNA were then predicted by miRNA target prediction databases to identify the target mRNA. Normal colon cell line CCD-18Co and CC cell lines HCT-116, HT-29, SW620 and SW480 were chosen, and qRT-PCR was conducted to detect miR-141 expression in these cell lines. qRT-PCR and Western blot were carried out to determine PHLPP2 mRNA and protein expression, respectively. Dual-luciferase reporter gene assay was performed to verify the targeting relationship between miR-141 and PHLPP2 3ʹUTR. CCK-8 assay and colony formation assay were carried out to detect cell proliferation. Meanwhile, tumor xenograft model in nude mice was constructed to assess CC cell tumorigenic ability in vivo. Results: miR-141 was markedly up-regulated in CC tissue. CC cell proliferation and in vivo tumorigenic ability were suppressed by miR-141 silencing but promoted by miR-141 overexpression. PHLPP2 was significantly down-regulated in cancer tissue. Dual-luciferase reporter gene assay indicated that miR-141 could bind to PHLPP2 3ʹUTR. PHLPP2 expression was noticeably elevated upon miR-141 deficiency but significantly inhibited upon miR-141 over-expression. CCK-8 and colony formation assay suggested that miR-141 facilitated CC cell proliferation by silencing PHLPP2. Conclusion: miR-141 promotes CC cell proliferation by targeted silencing PHLPP2.

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