Human prostate carcinoma cells express functional alphaIIb (beta) 3 integrin
Trikha, M.; Timar, J.; Lundy, S.K.; Szekeres, K.; Tang, K.; Grignon, D.; Porter, A.T.; Honn, K.V.
Cancer Research 56(21): 5071-5078
1996
ISSN/ISBN: 0008-5472 PMID: 8895766 Document Number: 465384
The integrin alpha-IIb-beta-3 was initially believed to be expressed only in cells from the megakaryocytic lineage, such as platelets or HEL cells. In this study, we report for the first time that human prostate carcinoma PC-3 and DU-145 cells express alpha-IIb-beta-3. Reverse transcription-PCR from HEL (positive control), PC-3, and DU-145 cells amplified a predicted alpha-IIb fragment that hybridized to the full-length alpha-IIb cDNA probe. DNA sequencing of the PCR fragments revealed 100% sequence homology to the corresponding extracellular domain of platelet alpha-IIb but minimal sequence homology to integrins alpha-v or alpha-5. An RNase protection assay was used to confirm the results from reverse transcription-PCR. An antisense riboprobe to alpha-IIb mRNA hybridized to total RNA from HEL, PC-3, and DU-145 cells, suggesting that alpha-IIb mRNA is transcribed in these tumor cells. In situ hybridization on surgical specimens from human prostate tumor tissue stained positive with an antisense riboprobe to alpha-IIb mRNA. The expression of alpha-IIb-beta-3 protein in PC-3 and DU-145 cells was demonstrated by Western and dot blotting and flow cytometry with monoclonal antibodies (mAbs) to alpha-IIb (MAB 1990),beta-3, and alpha-IIb-beta-3 (AP-2). A protein kinase C activator, phorbol 12-myristate 13-acetate, increased the adhesion of PC-3 cells to PAC-1, a mAb specific to the high-affinity state of alpha-IIb-beta-3, by more than 80-fold. The invasion of DU-145 cells through a reconstituted basement membrane was blocked 40-50% by mAbs AP-2 or PAC-1. These data collectively suggest that: (a) prostate tumor cells express alpha-IIb-beta-3; (b) surface expression of alpha-IIb-beta-3 integrin is regulated by protein kinase C; and (c) mAbs to this receptor inhibit invasion of prostate cancer cells through a reconstituted basement membrane.