The long noncoding RNA lnc-FANCI-2 intrinsically restricts RAS signaling and phosphorylation of Akt and Erk in HPV16-infected cervical cancer

Abstract

ABSTRACTWe recently discovered increased expression of a long noncoding RNA, lnc-FANCI-2, coinciding with cervical lesion progression from CIN1, CIN2-3 to cervical cancer. Viral E7 of high-risk HPVs and host transcription factor YY1 are two major factors promoting lnc-FANCI-2 expression. To explore possible roles of lnc-FANCI-2 in HPV-induced cervical carcinogenesis, we ablated the expression oflnc-FANCI-2in the HPV16-positive cervical cancer cell line, CaSki. Knock-out (KO) single cell clones expressed HPV16 oncogenes normally but displayed altered cell morphology when compared with the parental cells. Proteomic profiling of cytosolic and secreted proteins from the parental and KO cells showed that lnc-FANCI-2 regulates expression of a subset of cell surface and adhesion-related proteins, including inhibition of MCAM, PODXL2 and ECM1 and increased levels of ADAM8 and TIMP2. RNA-seq analyses revealed that, relative to the parental cells, KO cells exhibited significantly increased RAS signaling but decreased IFN pathways. In KO cells, phosphorylated Akt and Erk1/2, two important RAS pathway effectors, were increased more than 3-fold, accompanied by increase of IGFBP3, MCAM, VIM, and CCND2 (cyclin D2) and decrease of RAC3. Accordingly, high levels of lnc-FANCI-2 and lower levels of MCAM in cervical cancer patients are associated with improved survival. We found that lnc-FANCI-2 in CaSki cells interacts specifically with 32 host proteins, including H13, HNRH1, K1H1, MAP4K4, and RNPS1, and knockdown of MAP4K4 led to increase phosphorylation of Akt and Erk1/2. In summary, a key function of lnc-FANCI-2 is to intrinsically regulate RAS signaling, thereby affecting cervical cancer outcome.SignificanceExpression of lnc-FANCI-2 is related to cervical lesion progression. Knock-out (KO) or knock-down (KD) of lnc-FANCI-2 expression in HPV16-positive cervical cancer cells CaSki significantly increases RAS signaling, phosphorylation of Akt and Erk1/2, and increase of epithelial mesenchymal transition factors. lnc-FANCI-2 KO also regulates the expression of a subset of cell surface and adhesion-related proteins IGFBP3 and MCAM. A high level of lnc-FANCI-2 and lower level of MCAM in cervical cancer patients are associated with improved survival. lnc-FANCI-2 in CaSki cells interacts specifically with 32 host proteins, including MAP4K4. KD of MAP4K4 expression in CaSki cells led to increase phosphorylation of Akt and Erk1/2. Thus, one lnc-FANCI-2 function is to intrinsically regulate RAS signaling to impact cervical lesion progression.