Salivary Gland Cancer Patient-Derived Xenografts Enable Characterization of Cancer Stem Cells and New Gene Events Associated with Tumor Progression

Abstract

Salivary gland cancers (SGC) frequently present with distant metastases many years after diagnosis, suggesting a cancer stem cell (CSC) subpopulation that initiates late recurrences; however, current models are limited both in their availability and suitability to characterize these rare cells. Patient-derived xenografts (PDX) were generated by engrafting patient tissue onto nude mice from one acinic cell carcinoma (AciCC), four adenoid cystic carcinoma (ACC), and three mucoepidermoid carcinoma (MEC) cases, which were derived from successive relapses from the same MEC patient. Patient and PDX samples were analyzed by RNA-seq and Exome-seq. Sphere formation potential and tumorigenicity was assessed by sorting for Aldefluor (ALDH) activity and CD44-expressing subpopulations. For successive MEC relapses we found a time-dependent increase in CSCs (ALDHCD44), increasing from 0.2% to 4.5% (=0.033), but more importantly we observed an increase in individual CSC sphere formation and tumorigenic potential. A 50% increase in mutational burden was documented in subsequent MEC tumors, and this was associated with increased expression of tumor-promoting genes (, and ), decreased expression of tumor-suppressor genes (, and ), and higher expression of CSC-related proteins such as SOX2, MYC, and ALDH1A1. Finally, genomic analyses identified a novel- fusion in an ACC tumor and confirmed previously reported fusions (- and - Sequential MEC PDX models preserved key patient features and enabled the identification of genetic events putatively contributing to increases in both CSC proportion and intrinsic tumorigenicity, which mirrored the patient's clinical course. .

The Role of CD44 AND SOX-2 Cancer Stem cell Markers in The Development and Progression of Mucoepidermoid Carcinoma and Primary Squamous Cell Carcinoma of Salivary Glands

“…Salivary gland malignancies often show distant metastases several years after initial diagnosis, suggesting a subpopulation of cancer stem cells (CSCs) responsible for the late recurrences; however, the available models to characterize these rare cells are still limited. 29 In general, in salivary gland tumors; the hypothesis of cancer stem cell has not been fully examined. 30 Studies on other types of cancer revealed that cancer stem cells play a functional role in therapy resistance and tumor recurrence.…”

BMX-ARHGAP fusion protein maintains the tumorigenicity of gastric cancer stem cells by activating the JAK/STAT3 signaling pathway

“…Gene fusions remarkably alter gene structures leading to mutated protein products with an aberrant molecular function. They are usually involved in tumor progression through modulation of tumorigenic potential of the cancer stem cells [23]. The present study identified the high expression of BMX-ARHGAP fusion in GC.…”

Serial patient-derived orthotopic xenografting of adenoid cystic carcinomas recapitulates stable expression of phenotypic alterations and innervation

“…For those ‘personalized medicine’-intended purposes, the creation of ex vivo 3D tumor spheroids in multi-well plates [37] can serve as a reliable method for rapid drug screening assays. Multiple salivary gland cancers, including ACCs, have sphere-forming potential and share common ex vivo phenotypes in that similar (ALDH + CD44 high ) epithelial tumor stem cell populations form the highest numbers of spheres [38]. While this system is superior in the rapid evaluation of tumor stem cells and/or their response to drug or radiation-related therapeutics, the spheres created through cell sorting currently do not include the surrounding cell types.…”

“…Remarkably, we still obtained all ACC epithelial (cribriform, solid and tubular form) and environmental characteristics with single cell transplantations, arguably better than with undissociated subcutaneous PDX tissue as it mimicked the original human ACC biopsy. As such, PDOX can be applied to newly generated ACC primary cell lines, such as from our PDX-derived ACC11 [14], or FACS-sorted ACC epithelial tumor stem cells that are currently evaluated for PDX formation capacity [38], to compare their fidelity in maintaining similar phenotypic characteristics of the original specimen. In the future, it will be essential to determine whether ACC cell lines, which are often enriched in a specific cell type, are able to generate mixed PDOX tumors.…”