PC3 is a cell line characteristic of prostatic small cell carcinoma

Abstract

Background: The majority of the prostatic cancers are adenocarcinomas characterized by glandular formation and the expression of luminal differentiation markers androgen receptor (AR) and prostate-specific antigen (PSA). Most adenocarcinomas are indolent and androgen-dependent. Hormonal therapy that inhibits AR signaling produces symptomatic relief in patients with advanced and metastatic adenocarcinomas. Prostatic small cell neuroendocrine carcinoma (SCNC) is a variant form of prostate cancer (PC). In contrast to adenocarcinoma, the tumor cells of SCNC do not form glands and are negative for AR and PSA. SCNC is extremely aggressive and does not respond to hormonal therapy. The purpose of this study was to compare the important and relevant features of two most commonly used PC cell lines, LNCaP and PC3, with prostatic adenocarcinoma and SCNC.

Methods: Xenograft tumors of LNCaP and PC3 were prepared and compared with human prostatic adenocarcinoma and SCNC for the expression of key signaling molecules by immunohistochemistry and Western blot analysis.

Results: LNCaP cells express AR and PSA and their growth is inhibited by androgen withdrawal, similar to human prostatic adenocarcinoma. PC3 cells do not express AR and PSA and their proliferation is independent of androgen, similar to SCNC. Adenocarcinoma cells and LNCaP cells are negative for neuroendocrine markers and stem cell-associated marker CD44 while SCNC and PC3 cells are positive. LNCaP cells have identical cytokeratin profiles to adenocarcinoma while PC3 cells have cytokeratin profiles similar to SCNC.

Conclusion: LNCaP cells share common features with adenocarcinoma while PC3 cells are characteristic of SCNC.

Fig. 1

Distinct histologic features of prostatic adenocarcinoma and SCNC. The upper panel (A,B) are low and high power pictures of prostatic adenocarcinoma with cancerous glands recapitulating the morphologic features of normal prostatic glands/ducts, and the tumor cells forming glandular structures. Note that many tumor cells show prominent nucleoli. The lower panel (C,D) are low and high power pictures of prostatic SCNC with high-grade neuroendocrine morphology including diffuse, solid growth pattern, high N/C ratio, fine nuclear chromatin pattern, and frequent mitotic figures. Note that there is no glandular formation and no prominent nucleoli (H&E100× (A,C) and 400× (B,D)). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Fig. 2

Androgen receptor is expressed in prostatic adenocarcinoma and LNCaP cells but not in prostatic SCNC and PC3 cells. A: Immunohistochemical study with an anti-AR antibody shows positive staining in adenocarcinoma but not SCNC. The LNCaP xenograft tumor cells are positive for AR but the PC3 xenograft tumors are negative (IHC, 400× magnification). B: Western blotting shows that LNCaP cells express AR while PC3 cells do not. C,D: Growth assays show that withdrawal of androgen inhibits the growth of LNCaP cells but not PC3 cells. Blue line: media with FBS; red line: media with charcoal-stripped FBS. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Fig. 3

PSA is expressed in prostatic adenocarcinoma and LNCaP cells but not in prostatic SCNC and PC3 cells. A: Immunohistochemical study with an anti-PSA antibody shows positive staining in prostatic adenocarcinoma but not SCNC. The LNCaP xenograft tumor cells are positive for PSA but the PC3 xenograft tumors are negative (IHC, 400×). B: Western blot analysis shows that LNCaP cells express PSA but the PC3 cells do not. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Fig. 4

PC3 cells express NE cell markers but LNCaP cells do not. A: Western blot assay shows that PC3 cells, not LNCaP cells, express NE markers chromogranin A and NSE. B,C: show the results of qPCR studies showing higher mRNA levels for CgA and NSE in PC3 cells than in LNCaP cells. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Fig. 5

Neuroendocrine marker NSE is expressed in prostatic SCNC and PC3 cells but not in prostatic adenocarcinoma and LNCaP cells. Immunohistochemical study with an anti-NSE antibody shows positive staining in prostatic SCNC but not in adenocarcinoma. The LNCaP xenograft tumor cells are negative for NSE but the PC3 xenograft tumors are positive (IHC, 400×). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Fig. 6

CD44 is expressed in prostatic SCNC and PC3 cells but not in the luminal type tumor cells of prostatic adenocarcinoma and LNCaP cells. A: Immunohistochemical study shows positive staining in prostatic SCNC but not in adenocarcinoma (with the exception of rare NE tumor cells, arrow). The LNCaP xenograft tumor cells are negative for CD44 but the PC3 xenograft tumors are positive (IHC, 400×). B: qPCR study shows very low levels of CD44 mRNA in LNCaP cells but high levels in PC3 cells. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Fig. 7

CK8 is strongly and diffusely expressed in prostatic adenocarcinoma and LNCaP cells but only focally and weakly in SCNC and PC3 cells. Immunohistochemical study with an anti-CK8 antibody shows positive staining in prostatic adenocarcinoma cells but a dot-like staining pattern in tumor cells of SCNC. The LNCaP xenograft tumor cells are diffusely positive for CK18 but the PC3 xenograft diffuse tumors are only focally positive (IHC, 400×). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]