Interplay among transcription factors Ets21c, Fos and Ftz-F1 drives JNK-mediated tumor malignancy

Abstract

Cancer initiation and maintenance of the transformed cell state depend on altered cellular signaling and aberrant activities of transcription factors (TFs) that drive pathological gene expression in response to cooperating genetic lesions. Deciphering the roles of interacting TFs is therefore central to understanding carcinogenesis and for designing cancer therapies. Here, we use an unbiased genomic approach to define a TF network that triggers an abnormal gene expression program promoting malignancy of clonal tumors, generated in Drosophila imaginal disc epithelium by gain of oncogenic Ras (RasV12) and loss of the tumor suppressor Scribble (scrib1). We show that malignant transformation of the rasV12scrib1 tumors requires TFs of distinct families, namely the bZIP protein Fos, the ETS-domain factor Ets21c and the nuclear receptor Ftz-F1, all acting downstream of Jun-N-terminal kinase (JNK). Depleting any of the three TFs improves viability of tumor-bearing larvae, and this positive effect can be enhanced further by their combined removal. Although both Fos and Ftz-F1 synergistically contribute to rasV12scrib1 tumor invasiveness, only Fos is required for JNK-induced differentiation defects and Matrix metalloprotease (MMP1) upregulation. In contrast, the Fos-dimerizing partner Jun is dispensable for JNK to exert its effects in rasV12scrib1 tumors. Interestingly, Ets21c and Ftz-F1 are transcriptionally induced in these tumors in a JNK- and Fos-dependent manner, thereby demonstrating a hierarchy within the tripartite TF network, with Fos acting as the most upstream JNK effector. Of the three TFs, only Ets21c can efficiently substitute for loss of polarity and cooperate with RasV12 in inducing malignant clones that, like rasV12scrib1 tumors, invade other tissues and overexpress MMP1 and the Drosophila insulin-like peptide 8 (Dilp8). While rasV12ets21c tumors require JNK for invasiveness, the JNK activity is dispensable for their growth. In conclusion, our study delineates both unique and overlapping functions of distinct TFs that cooperatively promote aberrant expression of target genes, leading to malignant tumor phenotypes.

Hippo signaling promotes Ets21c-dependent apical cell extrusion in theDrosophilawing disc

“…In the Drosophila adult midgut, Ets21c expression is increased when JNK is activated by the JNK kinase hep (Mundorf et al, 2019). Ets21c also can promote tumor growth downstream of the JNK pathway (Külshammer et al, 2015;Toggweiler et al, 2016). Our results have confirmed that Ets21c functions downstream of JNK.…”

Microenvironmental autophagy promotes tumour growth

“…8i, j). Inhibition of either JNK or JAK–STAT in Ras V12 scrib −/− tumours reversed ROS accumulation 18 (Fig. 3k, l).…”

“…The following stocks were provided to us (18) y,w,ey-flp; Act>y + >Gal4, UAS-GFP/CyO; Frt82B, tub-Gal80, (19) y,w;UAS-Ras V12 /CyO; Frt82B/TM6B; (20) y,w; UAS-Ras V12 ,UAS-dome Δcyt2.1 /CyO; Frt82B, scrib 2 /TM6B and (21) UAS-Ras V12 , UAS-upd; Frt82B (T. Xu). (22) UAS-Ras V12 /CyO; Frt82B scrib 1 , UAS-bsk DN /TM6B , (23) w;UAS-ets21c long-RNAi ,UAS-Ras V12 /CyO; Frt82B scrib 1 , UAS-fos 39 / 19RNAi /TM6B , (24) w;UAS-Ras V12 /CyO; Frt82B scrib 1 , kay 3 /TM6B , (25) w;UAS-Ras V12 , exp::LacZ;Frt82B scrib 1 /S-T (M. Uhlirova) 18 , (26) y,w,ey-flp1;act>y+>GFP,UAS-GFP,egr 1 /CyO;FRT82,tub80/TM6B , (27) y,w, eyFLP1; G454, Act>y + >Gal4, UAS-mRFP; FRT82B, Tub-Gal80 (T. Igaki) 27,28 , (28) >Ras,egr 3 /CyO; FRT82B, scrib 1 /TM6B (M. Vidal) 17 , (29) atg13 Δ81 (T. P. Neufeld) 29 , (30) w, upd3 p[XP]d0495 (M. Zeidler), (31) pmCh-atg8a (E. Baehrecke) 6 , (32) UAS-Bsk DN (D. Bohmann), (33) Frt82B stat92E 85C9 (G. Halder), (34) UAS-s.Imp-L2 (E. Hafen) 30 , (35) UAS-dlg RNAi , UAS-Ras V12 (ref. 15), (36) UAS-dp110 D945A (S. M. Cohen).…”

“…JNK cooperates with Hippo (encoded by hpo )/Yorkie (encoded by yki )/Scalloped (encoded by sd ) signalling to drive tumour growth in Ras V12 scrib −/− animals 18 . To evaluate the role of Hippo signalling, we knocked down the Scrib polarity module component discs large (encoded by dlg1 ) while simultaneously overexpressing Ras V12 in half of the eye-antennal disc 15,20 .…”

The antimicrobial peptide Defensin cooperates with Tumour Necrosis Factor to drive tumour cell death in Drosophila

“…Having shown that Defensin restrict tumour growth, we sought to 143 determine the tissues that produced endogenous Defensin in the context of 144 tumour bearing. Previous studies have shown that Defensin is not produced 145 by imaginal discs or tumours (Bunker et al, 2015;Kulshammer et al, 2015). 146…”