Epithelial stem cell mutations that promote squamous cell carcinoma metastasis

Abstract

Squamous cell carcinomas (SCCs) originate in stratified epithelia, with a small subset becoming metastatic. Epithelial stem cells are targets for driver mutations that give rise to SCCs, but it is unknown whether they contribute to oncogenic multipotency and metastasis. We developed a mouse model of SCC by targeting two frequent genetic mutations in human SCCs, oncogene Kras G12D activation and Smad4 deletion, to mouse keratin 15-expressing (K15 + ) stem cells. We show that transgenic mice developed multilineage tumors, including metastatic SCCs. Among cancer stem cell-enriched (CSC-enriched) populations, those with increased side population (SP) cells correlated with epithelial-mesenchymal transition (EMT) and lung metastasis. We show that microRNA-9 (miR-9) contributed to SP expansion and metastasis, and miR-9 inhibition reduced the number of SP cells and metastasis. Increased miR-9 was detected in metastatic human primary SCCs and SCC metastases, and miR-9-transduced human SCC cells exhibited increased invasion. We identified α-catenin as a predominant miR-9 target. Increased miR-9 in human SCC metastases correlated with α-catenin loss but not E-cadherin loss. Our results demonstrate that stem cells with Kras G12D activation and Smad4 depletion can produce tumors that are multipotent and susceptible to EMT and metastasis. Additionally, tumor initiation and metastatic properties of CSCs can be uncoupled, with miR-9 regulating the expansion of metastatic CSCs. IntroductionSquamous cell carcinomas (SCCs) are derived from stratified epithelia present within the skin and oral cavity. A subset of aggressive SCCs become metastatic and lead to metastasis-associated death. The rate of metastasis in skin SCCs ranges from 0.1% to 10% (1), with poorly differentiated tumors and those with greater vertical tumor thickness having an increased risk of metastasis (2). Genetic alterations and intrinsic tumor cell properties controlling SCC metastasis are largely unknown. Genetically engineered mice provide a powerful tool for dissecting driver mutations that contribute to SCC initiation and metastasis. To date, very few genetic mutations causing spontaneous SCC formation and metastasis have been found, particularly metastasis to the lung, which is the leading cause of SCC-associated death (3). Mice with a Smad4 deletion in stratified epithelia develop spontaneous SCCs in the skin, oral cavity, and forestomach (4-6). Among these models, oral SCCs metastasize to lymph nodes (4), whereas skin and forestomach SCCs do not metastasize (5, 6).Because stratified epithelia undergo constant self-renewal and rapid turnover, it is believed that driver mutations for SCCs must initially occur in resident stem cells that renew these epithelia throughout life. In mouse skin, the hair follicle bulge harbors

Cancer Stem-like Cells Act via Distinct Signaling Pathways in Promoting Late Stages of Malignant Progression

“…However, it was not known whether CSC regulatory mechanisms change during disease progression, correlating with the enhanced recurrence and metastasis of high-grade SCCs (1), which could influence the selection of the most efficient therapy. In the study reported here, we generated lineages of SCC progression and showed that a high percentage of WD-SCCs exhibiting epithelial features progressed to PD and mesenchymal SCCs with enhanced metastasis capability, recapitulating the skin SCC progression reported in other mouse models (42). In contrast, previous reports suggested that spindle and EMT-like skin SCCs might arise by a route other than WD-SCCs after DMBA/TPA treatment, relying on a different cell of origin and/or lower requirement for inflammatory stimuli (22).…”

CD24 blunts oral squamous cancer development and dampens the functional expansion of myeloid-derived suppressor cells

“…A223-LG was derived from a mouse model of SCC with oncogene Kras (G12D) activation and Smad4 deletion in the epithelial progenitors. 45 We found that A223-LG-transplanted cancer exhibits significantly accelerated tumor growth in CD24 ¡/¡ mice comparing with CD24 C/¡ mice (Figs. 7A and B), which is consistent with the observation we made in the 4-NQO oral cancer model.…”

“…It was derived from transgenic mice that expressed a constitutively active Kras G12D mutant and simultaneous deletion of Smad4 in the epithelial progenitor cells. 45 Cells were cultured in DMEM supplemented with 10% FBS and 1% penicillin/streptomycin. After two passages, 1.5 £ 10 4 cells in 25 mL sterile 1X PBS were injected in the right lateral side of the tongue of CD24 C/¡ and CD24 ¡/¡ mice.…”

Prognostic Value of microRNA-224 in Various Cancers: A Meta-analysis

“…Finally, the remaining 20 publications [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] were combined in the meta analysis and the selection process presented by a flow chart which is shown in Fig. 1.…”