Estradiol-mediated inhibition of Sp1 decreases miR-3194-5p expression to enhance CD44 expression during lung cancer progression

Abstract

Background Sp1, an important transcription factor, is involved in the progression of various cancers. Our previous studies have indicated that Sp1 levels are increased in the early stage of lung cancer progression but decrease during the late stage, leading to poor prognosis. In addition, estrogen has been shown to be involved in lung cancer progression. According to previous studies, Sp1 can interact with the estrogen receptor (ER) to coregulate gene expression. The role of interaction between Sp1 and ER in lung cancer progression is still unknown and will be clarified in this study. Methods The clinical relevance between Sp1 levels and survival rates in young women with lung cancer was studied by immunohistochemistry. We validated the sex dependence of lung cancer progression in EGFRL858R-induced lung cancer mice. Wound healing assays, chamber assays and sphere formation assays in A549 cells, Taxol-induced drug-resistant A549 (A549-T24) and estradiol (E2)-treated A549 (E2-A549) cells were performed to investigate the roles of Taxol and E2 in lung cancer progression. Luciferase reporter assays, immunoblot and q-PCR were performed to evaluate the interaction between Sp1, microRNAs and CD44. Tail vein-injected xenograft experiments were performed to study lung metastasis. Samples obtained from lung cancer patients were used to study the mRNA level of CD44 by q-PCR and the protein levels of Sp1 and CD44 by immunoblot and immunohistochemistry. Results In this study, we found that Sp1 expression was decreased in premenopausal women with late-stage lung cancer, resulting in a poor prognosis. Tumor formation was more substantial in female EGFRL858R mice than in male mice and ovariectomized female mice, indicating that E2 might be involved in the poor prognosis of lung cancer. We herein report that Sp1 negatively regulates metastasis and cancer stemness in E2-A549 and A549-T24 cells. Furthermore, E2 increases the mRNA and protein levels of RING finger protein 4 (RNF4), which is the E3-ligase of Sp1, and thereby decreases Sp1 levels by promoting Sp1 degradation. Sp1 can be recruited to the promoter of miR-3194-5p, and positively regulate its expression. Furthermore, there was a strong inverse correlation between Sp1 and CD44 levels in clinical lung cancer specimens. Sp1 inhibited CD44 expression by increasing the expression of miR-3194-5p, miR-218-5p, miR-193-5p, miR-182-5p and miR-135-5p, ultimately resulting in lung cancer malignancy. Conclusion Premenopausal women with lung cancer and decreased Sp1 levels have a poor prognosis. E2 increases RNF4 expression to repress Sp1 levels in premenopausal women with lung cancer, thus decreasing the expression of several miRNAs that can target CD44 and ultimately leading to cancer malignancy.

LPS inhibits TRIM65 expression in macrophages and C57BL/6J mouse by activating the ERK1/2 signaling pathway

“…By contrast, Sp1 is a C2H2-type zinc finger protein and an ubiquitous transcription factor belonging to the Sp/Krüppel-like factor 4 family of proteins ( 42 ). Sp1 has been reported to regulate a number of cellular processes, such as immune responses, cell differentiation, cell proliferation and apoptosis ( 1 , 43 , 44 ) Post-translational modifications, such as phosphorylation, sumoylation, acetylation, glycosylation and proteolytic processing can significantly alter Sp1 activity, resulting in either activation or repression ( 43 , 44 ). For example, Sp1 phosphorylation by JNK1/2 kinases increases protein stability ( 45 ).…”

Specificity Proteins (Sp) and Cancer

“…Some of the miRNAs in Table 2 and others are also regulated by Sp TF in cancer cells. For example, Sp1 induces expression of multiple miRNAs in lung cancer cells (miRNA-3194-5p, miRNA-218-5p, miRNA-193-5p, miRNA-182-5p and miRNA-135-5p), [ 74 ] miRNA-200 in breast cancer cells [ 75 ], and miRNA-365 in Hela cells [ 76 ]. In contrast, Sp1 decreases miR-335 expression in ovarian cancer cells, and this is one of the rare reported examples of Sp1 as a transcriptional receptor [ 77 ].…”

Cell adhesion molecules and immunotherapy in advanced non-small cell lung cancer: Current process and potential application

“…It can inhibit tumor stemness and metastasis. CD44 expression can be inhibited by Sp1 through inducing the expression of miR-3194-5p, miR-218-5p, miR-193-5p, miR-182-5p and miR-135-5p ( 88 ). Hyaluronan-CD44/HA-mediated motility receptor signaling pathway is overexpressed in NSCLC and associated with cell proliferation and survival ( 89 ).…”