Tissue-type plasminogen activator predicts endocrine responsiveness of human pancreatic carcinoma cells

Estrogen receptor (ER) has been found in human pancreatic carcinoma, but the potential benefit of endocrine therapy never has been assessed adequately. The aim of this study was to determine whether the presence of ER can be used as an indicator of hormone responsiveness, and whether modulation of tissue-type plasminogen activator (t-PA) by ER can identify hormone-responsive pancreatic carcinomas.

The authors investigated ER status and hormonal regulation of t-PA in nine human pancreatic carcinoma cell lines, AsPC-1, BxPC-3, Capan-1, Capan-2, Hs-700T, Hs-766T, MiaPaCa-2, PANC-1, and SUIT-2. Furthermore, to examine whether estrogen dependency of t-PA production in pancreatic carcinoma cells correlated with responsiveness to endocrine therapy, the in vivo effects of various endocrine agents on the growth of the nine pancreatic cell lines transplanted into nude mice were examined.

In a 17 beta-estradiol (E2)-binding assay, three of the nine pancreatic carcinoma cell lines (BxPC-3, Capan-2, and MiaPaCa-2) contained measurable levels of estradiol binding sites in vitro and in vivo using tumors transplanted into nude mice. Although t-PA was present in the culture medium in eight of the nine pancreatic carcinoma cell lines (not in Hs-700T), t-PA production was regulated by estrogen via an ER system in vitro only in the Capan-2 cell line. E2 injection into tumor-bearing mice showed acceleration of tumor growth only in Capan-2 tumors. Administration of a competitive ER antagonist, toremifene, and a luteinizing hormone-releasing hormone analogue, leuprorelin acetate (LEU), to Capan-2-bearing mice significantly reduced the rate of tumor growth, although there was no actual shrinkage of tumor mass. These agents failed to exert any antitumor effect on the other eight pancreatic cell lines. Although aromatase inhibitors, CGS 20267 and vorozole did not modify the in vivo growth of the nine pancreatic carcinoma cell lines significantly, the combined use of aromatase inhibitors with LEU exhibited a synergistic antitumor effect on Capan-2-bearing mice. Medroxyprogesterone acetate treatment significantly reduced the tumor volume of Capan-2 and also caused delayed growth in two other cell lines, AsPC-1 and MiaPaCa-2.

The estrogen dependency of t-PA production may clarify the functional state of ER in human pancreatic carcinoma cells. This finding may aid in planning endocrine therapy for patients with this lethal cancer.