Wnt/β-catenin signalling induces MLL to create epigenetic changes in salivary gland tumours

Abstract

We show that activation of Wnt/b-catenin and attenuation of Bmp signals, by combined gain-and loss-of-function mutations of b-catenin and Bmpr1a, respectively, results in rapidly growing, aggressive squamous cell carcinomas (SCC) in the salivary glands of mice. Tumours contain transplantable and hyperproliferative tumour propagating cells, which can be enriched by fluorescence activated cell sorting (FACS). Single mutations stimulate stem cells, but tumours are not formed. We show that b-catenin, CBP and Mll promote self-renewal and H3K4 tri-methylation in tumour propagating cells. Blocking b-catenin-CBP interaction with the small molecule ICG-001 and small-interfering RNAs against b-catenin, CBP or Mll abrogate hyperproliferation and H3K4 tri-methylation, and induce differentiation of cultured tumour propagating cells into acini-like structures. ICG-001 decreases H3K4me3 at promoters of stem cell-associated genes in vitro and reduces tumour growth in vivo. Remarkably, high Wnt/b-catenin and low Bmp signalling also characterize human salivary gland SCC and head and neck SCC in general. Our work defines mechanisms by which b-catenin signals remodel chromatin and control induction and maintenance of tumour propagating cells. Further, it supports new strategies for the therapy of solid tumours.

WNT signaling drives cholangiocarcinoma growth and can be pharmacologically inhibited

“…Thus, we specifically inhibited either the CTNNB1-CTBP interaction or the activity of PORCN in human CC cells in vitro with the small molecule ICG-001 or C-59, respectively. These compounds have been used to great effect in other systems (47,(50)(51)(52)(53) to therapeutically inhibit the canonical WNT signaling cascade. Five human CC cell lines, CC-LP-1, SNU-1079, WITT-1, SNU-1196, and CC-SW-1 (39, 40, 54), expressed both CTNNB1 and WNT7B in vitro (Supplemental Figure 5A; negative staining control, Supplemental Figure 8B).…”

A Small-Molecule Antagonist of the β-Catenin/TCF4 Interaction Blocks the Self-Renewal of Cancer Stem Cells and Suppresses Tumorigenesis

“…Mouse salivary gland CSCs were isolated and cultured in DMEM/F12 (Invitrogen) supplemented with 20% KSR, nonessential minimal amino acids, penicillin, streptomycin, L-glutamine, and b-mercaptoethanol. The cell identity was tested by PCR phenotyping for b-catenin and Bmpr1a (16).…”

“…SW480 reporter cells and mouse salivary gland CSCs were trypsinized and seeded as single cells into the sphere culture medium (F12:DMEM 1:1, 1Â B-27 supplement, 20 ng/mL EGF, 20 ng/mL FGF, 0.5% methylcellulose) with or without treatment (16,19). After 10 days, spheres were counted under a phase contrast microscope, and pictures were taken by AF6000 and DFC350FX (Leica).…”

“…A CD24 high CD29 þ cell population (Fig. 6B, encircled in red in the left plot and following purification in the right plot) was characterized as salivary gland CSCs by their potent sphere-forming capacity in culture and their high (16). Remarkably, the expression of stem cell-associated, chromatin modifier and Wnt target genes that are highly expressed in the salivary gland CSCs were downregulated by LF3 at 30 mmol/L, by ICG-001 at 25 mmol/L, by the recently identified new Wnt inhibitor iCRT3 (27) at 60 mmol/L, and by b-catenin siRNA (Fig.…”

“…Deregulated Wnt signaling is not only important for cancer initiation, but is also crucial in late-stage cancers and in metastasis formation (13,14). Recent studies have shown that cancer stem cells (CSC) in various tumors exhibit deregulated Wnt/b-catenin signaling (15)(16)(17) and require higher Wnt activity than differentiated cancer cells to maintain their self-renewal and tumorigenic properties. This feature may be useful in specifically targeting CSCs, a crucial factor in combatting cancer recurrence (18,19).…”