Development of an in vitro model for investigating the properties of human prostate epithelial cells and prostatic carcinoma cells

Abstract

Prostate cell lines were derived from two regions of prostate tissue from the same patient. The objective was to produce cell lines (as a useful in vitro model) from these two different regions which exhibit different properties for carcinoma development. The tissue was obtained from patients suffering from benign prostate hyperplasia undergoing trans-urethral resection. Tissue was taken from the deep (peripheral) and superficial (peri-urethral) areas. The cells were immortalised by transduction with constructs over expressing the cdk4 and hTERT genes. These cell lines were then characterised for their cellular phenotypes utilized for radiation transformation studies and utilized to investigate the role of plant derived polyphenols on normal and tumour cells.

The cell line from the superficial region (P21s) was treated to fractionated doses of gamma radiation and a transformed cloned cell line was derived (P21s 40Gy (clone-a)). The cell line from the deep region (P21d) was found to consist of a mixed population of abnormal cells and a transformed cloned cell line was derived from it (P21d 0Gy (clone-a). In an attempt to obtain a normal P21d cell line cloned cell lines from early passage P21d cells were established. All seven cloned lines were abnormal with an average of 80 chromosomes per cell, invasive using a Matrigel assay and produced anchorage independent colonies. All cell lines were fully characterised with immunocytochemistry, chromosome analysis, invasion assays, and anchorage independent colony formation. P21s expressed basal cell markers (cytokeratin 5 (CK5) and 14), were positive for stem cell markers (prostate specific stem cell antigen PSCA, CK6), positive for p16, p63 and telomerase expression and negative for c-Myc expression. P21s was not invasive in a Matrigel assay and did not produce anchorage independent colony formation. P21d and P21d 0Gy (clone-a) also expressed CK5, CK14, PSCA, CK6, and telomerase but not p16 or p63 and showed an increase in expression of nuclear c-Myc, highly invasive and produced anchorage independent colonies. P21s 40Gy (clone-a) expressed CK5, CK14, PSCA, CK6, telomerase and p63, produced anchorage independent colonies, and was weakly positive for c-Myc expression. Spectral karyotyping analysis (SKY) showed P21s had a normal chromosome complement except an additional chromosome 20 whereas the P21s 40Gy (clone-a), P21d and P21d 0Gy (clone-a) cell lines had an abnormal chromosome complement with P21d and P21d 0Gy (clone-a) cell lines expressing multiple copies of every chromosome including loss of the Y chromosome. These results were echoed in the single nucleotide polymorphism chip (SNP) results which showed P21s as normal but P21d and P21d 0Gy (clone-a) to have large deletion and amplification regions that correlated with the SKY analysis.

No differential cytotoxic response was noted between normal and abnormal cell lines including prostatic carcinoma cell lines LNCaP and PC-3 following treatment with strawberry polyphenol compounds. Most reports of a cytotoxic response to tumour cells in the literature did not compare the response to normal cells and used established cell lines. Human lymphocytes were also tested and all compounds were toxic in high doses. Polyphenol and ellagitannin rich polyphenol fractions were very cytotoxic and the anthocyanin rich fraction less toxic. In contrast to the lack of a direct differential cytotoxic effect, plant polyphenols did produce a protective effect to a carcinogenic insult. However a protective effect was noted via micronucleus assay with 3 hour incubation with the polyphenol rich fraction prior to radiation treatment.

Finally, the expression and association of metabolic enzymes within the cells cytosol were investigated. The P21s cells were found to express both isoforms of LDH and so thought to be able to metabolise anaerobically and aerobically. P21d and P21d 0Gy (clone-a) cells were found to only express one isoform in the complex and so it was assumed that these cells favoured anaerobic metabolism of ATP in correlation to the Warburg effect. c-Myc association with compounds in the cell cytosol of P21s cells existed whereas, abnormal cells lost this association along with up-regulation of c-Myc expression and down stream targets of c-Myc in the nuclei.

Thus these newly established human prostate cell lines provide a useful model system for investigating the biology of the prostate and prostate cancer.