Characterization of high‐affinity receptors for bombesin/gastrin releasing peptide on the human prostate cancer cell lines PC‐3 and DU‐145: Internalization of receptor bound ¹²⁵I‐(Tyr⁴) bombesin by tumor cells

Abstract

Specific receptors for bombesin/gastrin releasing peptide (GRP) on the androgen-independent human prostate cancer cell lines PC-3 and DU-145 were characterized. No specific binding of 125I-[Tyr4]-bombesin to the androgen-dependent human prostate cancer cell line LNCaP was detectable. The binding of 125I-[Tyr4]-bombesin to PC-3 and DU-145 cells was found to be time- and temperature-dependent, saturable, and reversible. Scatchard analysis revealed a single class of binding sites with high affinity (Kd 9.8 x 10(-11) M for PC-3, and 9.1 x 10(-11) M for DU-145 cells at 25 degrees C) and with a binding capacity of 44,000 binding sites/cell and 19,000 binding sites/cell, respectively. Bound 125I-[Tyr4]-bombesin was rapidly internalized by PC-3 cells. The nonhydrolyzable GTP analog GTP-gamma-S caused a dose-dependent inhibition of 125I-[Tyr4]-bombesin binding to PC-3 and DU-145 cells, indicating that a G-protein (guanine nucleotide-binding protein) couples the bombesin receptor to intracellular effector systems. Bombesin and GRP(14-27) inhibited the binding of 125I-[Tyr4]-bombesin to both cell lines in a dose-dependent manner with inhibition constants (Ki) of 0.5 nM and 0.4 nM, respectively. Both cell lines express the bombesin/GRP preferring bombesin receptor subtype, since, in displacement studies, neuromedin B was more than 200 times less potent than bombesin and GRP(14-27) in inhibiting the binding of 125I-[Tyr4]-bombesin. Two synthetic bombesin/GRP antagonists, RC-3095 and RC-3110, powerfully inhibited the specific binding of 125I-[Tyr4]-bombesin with Ki 0.92 nM and 0.26 nM on PC-3 cells, and 3.3 nM and 0.89 nM on DU-145 cells, respectively. These findings indicate that the PC-3 and DU-145 human prostate cancer cell lines possess specific high-affinity receptors for bombesin/GRP, and are suitable models for the evaluation of the antineoplastic activity of new bombesin/GRP antagonists in the treatment of androgen-independent prostate cancer.

Bombesin functionalized gold nanoparticles show in vitro and in vivo cancer receptor specificity

“…As part of our ongoing efforts toward the development of tumor-specific gold nanoparticles, we chose conjugations of AuNPs with BBN peptide analogs because this peptide library has demonstrated high affinity toward GRP receptors in vivo (overexpressed in prostate, breast, and small-cell lung carcinoma). Schally and co-workers have shown that there are 44,000 bombesin receptor sites on human prostate cancer (PC-3) cells (19). A number of clinical trials in progress are using BBN peptide analogs to target GRP receptors present in prostate cancer for imaging applications (20).…”

Neurotensin stimulates mitogenesis of prostate cancer cells through a novel c-Src/Stat5b pathway

“…Proliferation and DNA synthesis of PC3 cells (Seethalakshmi et al, 1997;Lee et al, 2001;Hassan and Carraway, 2006), and also of LNCaP cells in the absence of androgen (Sehgal et al, 1994;Lee et al, 2001), are stimulated when cells are treated with NT. Receptors for bombesin (Reile et al, 1994;Aprikian et al, 1996;Xiao et al, 2002), NT (Seethalakshmi et al, 1997;Dal Farra et al, 2001;Petit et al, 2001) and PTHrP (Tovar-Sepulveda and Falzon, 2002) are expressed by PC3, LNCaP and/or DU145 prostate cancer cells and have been characterized with respect to proliferative function. Thus, mitogenic neuropeptides that are secreted by NE-like cells can activate specific membrane-bound receptors on the surface of prostate cancer cells, resulting in increased proliferation and DNA synthesis.…”

Novel 111In-labelled bombesin analogues for molecular imaging of prostate tumours

“…Prostate tumours overexpress GRP receptors [11,14,[18][19][20][21]. In an autoradiographic study, Markwalder and Reubi found the GRP receptor to be expressed in high density on invasive prostate carcinomas and proliferative intraepithelial prostate lesions, mostly prostatic intraepithelial neoplasias, whereas normal prostate tissue and, in most cases, hyperplastic prostate tissue were GRP receptornegative [14].…”