BOTH ESTRADIOL-17-BETA AND TAMOXIFEN INDUCE APOPTOSIS IN HUMAN LARYNX-CARCINOMA CELLS OF HEP-2 LINE

Estrogens and their antagonist tamoxifen were proposed for use in tumo r hormonotherapy, although up to now there has been no uniformity in t he approaches to their utilization as well as in the explanation of th e mechanisms of their action on different cell targets. We showed that estradiol-17 beta (10(-7)-10(-5) M) and tamoxifen (10(-7)-10(-5) M) i nduced apoptosis in human larynx carcinoma cells of HEp2 line. Apoptot ic cells were detected using both morphological (chromatin condensatio n, nucleus fragmentation and appearance of apoptotic bodies) and bioch emical (internucleosomal DNA cleavage revealed after electrophoresis i n agarose gel) testing. The velocity of apoptosis development depended on the concentration of the above mentioned agents. With the elevatio n of estradiol-17 beta or tamoxifen concentration from 10(-7) to 10(-5 ) M, the time necessary for maximal apoptosis development was shorteni ng from 8 to 4 days. It is noteworthy that the relative amount of the apoptotic cells after their durable treatment with estradiol-17 beta o r tamoxifen considerably decreased. At present, the mechanisms for suc h bi-phase character of apoptosis development are not clear, though th e existence of human larynx carcinoma HEp-2 cells resistant to apoptos is induced by estradiol-17 beta or tamoxifen cannot be excluded. It sh ould be also noted that apoptosis occurring in these tumor cells after their durable (8-10 days) growing in a serum-free culture medium was not accompanied by the appearance of well expressed ''DNA ladder'', al though characteristic apoptosis-related changes in cell morphology cou ld be clearly seen here. Thus, hormonotherapeutical drugs or growth fa ctors' deficiency could switch on diverse apoptosis mechanisms in HEp- 2 carcinoma cells.