miR-181a decelerates proliferation in cutaneous squamous cell carcinoma by targeting the proto-oncogene KRAS

Abstract

Cutaneous squamous cell carcinoma (SCC) is the second most common human skin cancer with a rapidly increasing incidence among the Caucasian population. Among the many regulators, responsible for cancer progression and growth, microRNAs (miRNA) are generally accepted as key players by now. In our current study we found that microRNA-181a (miR-181a) shows low abundance in SCC compared to normal epidermal skin. In vitro, miRNA downregulation in normal primary keratinocytes induced increased proliferation, while in vivo miR-181a downregulation in HaCaT normal keratinocytes showed tumor-like growth increase up to 50%. Inversely, upregulation of these miRNAs in cancer cells lead to reduced cellular proliferation and induction of apoptosis in vitro. An in vivo therapeutic model with induced miR-181a expression in SCC13 cancer cells reduced tumor formation in mice by 80%. Modulation of miR-181a levels showed an inverse correlation with the proto-oncogene KRAS both on mRNA and protein level by direct interaction. Knockdown of KRAS mimicked the anti-proliferative effects of miR-181a overexpression in patient-derived SCC cells and abolished the enhanced viability of HaCaT cells following miR-181a knockdown. Furthermore, phospho-ERK levels correlated with KRAS levels, suggesting that the observed effects were mediated via the MAPK signaling pathway. miR-181a seemed regulated during keratinocyte differentiation probably in order to amplify the tumor suppressive character of differentiation. Taken together, miR-181a plays a crucial tumor suppressive role in SCC by targeting KRAS and could be a promising candidate for a miRNA based therapy.

Differential Role of the RasGEFs Sos1 and Sos2 in Mouse Skin Homeostasis and Carcinogenesis

“…Consistently, transgenic mice expressing a dominant Sos1 isoform in the skin showed a hyperproliferative response in keratinocytes in vitro and also in vivo, leading to tissue hyperplasia (22). On the other hand, different bioinformatic tools predict that Sos1 is a putative target gene for miR-181a (27), which is also known to reduce proliferation in primary keratinocytes (28). In this regard, upon Ras elimination, keratinocytes cease proliferation and enter into senescence without any signs of apoptosis induction (19).…”

miR‑186 promotes tumor growth in cutaneous squamous cell carcinoma by inhibiting apoptotic protease activating factor‑1

“…A number of previous studies have demonstrated that miRNAs are involved in the pathogenesis of a number of human diseases, particularly different types of cancer ( 12 , 31 , 32 ). Aberrant miRNA expression is frequently observed in cancer, including pancreatic, breast and various types of skin cancer ( 33 – 35 ). Increasing numbers of miRNAs have been identified as critical regulators in the initiation and progression of cSCC, including miR-1, miR-34a, miR-124 and miR-125b ( 36 – 39 ).…”

The Role of MicroRNAs in Epidermal Barrier

“…Upregulation of JNK by galectin-7 [19] Increased keratinocyte differentiation with involucrin expression by oleic acid [20] p63, Skp2 and Msi2 Promotion of cell cycle exit in mouse skin [21] miR-574 ↑ p63 As direct targets of iASPP [22] miR-720 ↑ miR-24 ↑ PAK4 Control of actin cable formation [23] miR-23b-3p ↑ TGIF1 Interference in TGF-β/SMAD signaling [24] miR-378b ↑ NKX3.1 [25] miR-30a ↑ LOX, IDH1, AVEN Barrier function defects in aged epidermis [26] miR-184 ↑ Upregulation of cyclin E and p21 cyclin-dependent kinase inhibitor in a SOCE-dependent manner [27] miR-181a ↑ cell differentiation under high calcium or UVA exposure [28,29] miR [33] miRNAs targeted by p63 miR-34a ↑ SIRT6 miR-34a and miR-34c as direct targets of p63 [34,35] miR-34a ↑ KLK4 Induction of a senescent phenotype in keratinocytes [36] ↑: upregulation (increase), ↓: downregulation (decrease).…”

“…Substantial data associated with miRNAs, either upregulated or downregulated, and keratinocyte proliferation have been reported in psoriasis. The downregulated miRNAs include miR-125b, miR-181b-5p, miR-520a, miR-194, miR-217, miR-138, miR-320b, miR-150, miR-145-5p, miR-20a-3p, miR-876-5p, miR-99a, miR-187, miR-548a-3p, miR-330, and miR-146a AKT3 [47] miR-181b-5p AKT3, TRL4 [47,48] miR-520a AKT [49] miR-320b AKT3 [50] miR-194 GRHL2 [51] miR-217 [52] miR-138 hTERT [53] miR-150 HIF-1α, VEGFA [54] miR-145-5p MLK3 [55] miR-20a-3p SFMBT1 [56] miR-876-5p ANG-1 [57] miR-99a FZD5/FZD8 [58] miR-187 CD276 [59] miR-548a-3p PPP3R1 [60] miR-330 CTNNB1 [61] miR-146a EGFR Psoriasis, cSCC [62,63] miR-96-5p BNP3 Wound healing [64] miR-181a KRAS cSCC [29] miR-99b IGF-1R Condyloma acuminatum [65] miR-203 ∆Np63 Epidermodysplasia verruciformis [66] miR-130a STK40 [79] miR-122-5p SPRY2 [80] miR-223 PTEN [81] miR-17-3p MYOT Wound healing [82] miR-126 PLK2 [83] ↑: upregulation, ↓: downregulation.…”

“…Downregulation of miR-181a in cSCC promotes keratinocyte proliferation by targeting proto-oncogene Kirsten rat sarcoma 2 viral oncogene homolog (KRAS) [29]. The increased expression of miR-181a during keratinocyte differentiation induced by high calcium or UVA irradiation [28,29] suggests that the imbalance between keratinocyte proliferation and differentiation has a considerable impact on skin barrier dysfunction. RAS is a small GTPase protein that mediates the reversible conversion between GDP-loaded inactive and GTP-loaded active forms.…”