Enrichment of human prostate cancer cells with tumor initiating properties in mouse and zebrafish xenografts by differential adhesion

Abstract

BACKGROUND Prostate tumor-initiating cells (TICs) have intrinsic resistance to current therapies. TICs are commonly isolated by cell sorting or dye exclusion, however, isolating TICs from limited primary prostate cancer (PCa) tissues is inherently inefficient. We adapted the collagen adherence feature to develop a combined immunophenotypic and time-of-adherence assay to identify human prostate TICs. METHODS PCa cells from multiple cell lines and primary tissues were allowed to adhere to several matrix molecules, and fractions of adherent cells were examined for their TIC properties. RESULTS Collagen-I rapidly-adherent PCa cells have significantly higher clonogenic, migration, and invasion abilities, and initiated more tumor xenografts in mice when compared to slowly-adherent and no-adherent cells. To determine the relative frequency of TICs among PCa cell lines and primary PCa cells, we utilized zebrafish xenografts to define the tumor initiation potential of serial dilutions of rapidly-adherent α2β1hi/CD44hi cells compared to non-adherent cells with α2β1low/CD44low phenotype. Tumor initiation from rapidly-adherent α2β1hi/CD44hi TICs harboring the TMPRSS2:ERG fusion generated xenografts comprising of PCa cells expressing Erg, AMACR, and PSA. Moreover, PCa-cell dissemination was consistently observed in the immune-permissive zebrafish microenvironment from as-few-as 3 rapidly-adherent α2β1hi/CD44hi cells. In zebrafish xenografts, self-renewing prostate TICs comprise 0.02–0.9% of PC3 cells, 0.3–1.3% of DU145 cells, and 0.22–14.3% of primary prostate adenocarcinomas. CONCLUSION Zebrafish PCa xenografts were used to determine that the frequency of prostate TICs varies among PCa cell lines and primary PCa tissues. These data support a paradigm of utilizing zebrafish xenografts to evaluate novel therapies targeting tumor initiating cells in prostate cancer.

Embryonic zebrafish xenograft assay of human cancer metastasis

“…The extra-uterine development of hundreds of eggs also permits a greater number of studies in genetically identical organisms. Since the first reported xenotransplantation of human cells into zebrafish ( Lee et al , 2005), many laboratories have shown that zebrafish embryos are useful for the study of other facets of tumour biology including cancer-induced angiogenesis ( Haldi et al , 2006); cancer cell invasion and metastasis ( de Boeck et al , 2016; Marques et al , 2009); cancer stem cell growth ( Bansal et al , 2014; Chen et al , 2017); interaction of cancer cells with the host ( Feng & Martin, 2015); and drug screening ( Corkery et al , 2011; Gibert et al , 2013). Importantly, the development of human tumours and their response to chemotherapeutic treatment in zebrafish embryos is comparable to that observed in mouse xenograft assays ( Fior et al , 2017).…”

BMI-1 Targeting Interferes with Patient-Derived Tumor-Initiating Cell Survival and Tumor Growth in Prostate Cancer

“…Previously, we developed a surrogate self-renewal assay that allowed us to isolate TICs from PCa tissue based on α2β1-integrin (also called CD49b/CD29) and CD44 protein expression (6). Herein, we demonstrate that in prostate TICs, BMI-1 is overexpressed and functionally regulates their survival and maintenance.…”

Tumor-Initiating Cells: Emerging Biophysical Methods of Isolation

“…Bansal et al isolated prostate TICs from other cancer cells by allowing them to bind to collagen-coated surfaces for a short period of time. They found that TICs bound faster, and by washing away other cells, cancer cells with stem-like properties could be enriched [103]. Zhang et al applied the same idea in a more controlled manner to isolate breast cancer TICs.…”