Rapid selection of mesenchymal stem and progenitor cells in primary prostate stromal cultures

Carcinoma-associated fibroblasts (CAFs) are a dominant component of the tumor microenvironment with pro-tumorigenic properties. Despite this knowledge, their physiologic origins remain poorly understood. Mesenchymal stem cells (MSCs) can be recruited from the bone marrow to areas of tissue damage and inflammation, including prostate cancer. MSCs can generate and have many overlapping properties with CAFs in preclinical models.

Multiparameter flow cytometry and multipotent differentiation assays used to define MSCs in primary prostate stromal cultures derived from young (<25 yrs) organ donors and prostate cancer patients compared with bone marrow-derived stromal cultures. Population doubling times, population doublings, cell size, and differentiation potential determined under multiple culture conditions, including normoxia, hypoxia, and a variety of media. TGF-β measured by ELISA.

MSCs and stromal progenitors are not only present in normal and malignant prostate tissue, but are quickly selected for in primary stromal cultures derived from these tissues; becoming the dominant population within just a few passages. Growth potential inversely associated with TGF-β concentrations. All conditions generated populations with an average cell diameter >15 µm. All cultures tested had the ability to undergo osteogenic and chondrogenic differentiation, but unlike bone marrow-derived MSCs, primary stromal cultures derived from normal prostate tissue lack adipogenic differentiation potential. In contrast, a subset of stromal cultures derived from prostate cancer patients retain the ability to differentiate into adipocytes; a property that is significantly suppressed under hypoxic conditions in both bone marrow- and prostate-derived MSCs.

Primary prostate stromal cultures are highly enriched in cells with an MSC or stromal progenitor phenotype. The use of primary cultures such as these to study CAFs raises interesting implications when considering their overlapping properties. The lack of adipogenesis in stromal cultures derived from normal prostates suggests they have a lineage-restricted progenitor phenotype. The retention of adipogenic differentiation in cultures from a subset of prostate cancer patients suggests the active recruitment of less committed progenitors or MSCs from the bone marrow as a function of disease progression. This recruitment can potentially be exploited for prognostic purposes or a cell-based platform for the systemic delivery of cytotoxic agents to sites of prostate cancer.