Risk factors commonly associated with breast cancer were studied in relation to: (1) tumor estrogen receptor (ER) or progesterone receptor (PR) status and (2) the presence of tumor hormone receptors in relation to subsequent survival. For 171 Israeli women diagnosed with breast cancer in 1976 to 1979, tumor hormone receptor status (positive if greater than 20 fmol receptors/mg protein; negative if less than or equal to 20 fmol/mg) and survival as of April 1984 were ascertained. There were 77 ER- versus 94 ER+ and (for 134 PR analyses) 69 PR- versus 65 PR+. Although ER status and PR status were found to be highly positively related, the epidemiologic features of women with an ER+ tumor were different from those with a PR+ tumor. Age tended to be associated positively with both ER+ and PR+. Being postmenopausal, older at menopause or at first birth, nulliparous, having more years of schooling, and a higher body mass index for older women or a lower body mass index for younger women were correlated positively with ER and negatively with PR. Among women with Stage III or IV tumors at diagnosis significant differences existed: restricted mean survival for follow-up time was 47.2 months for ER-, 73.8 months for ER+, 45.8 months for PR-, and 61.9 months for PR+. The combined hormone effects on survival at Stages III to IV showed a similar trend: restricted mean survival of 38.4 months for ER-PR-, intermediate survival with one positive hormone receptor status, and 74.6 months for ER+PR+.

Prolonged exposure of cells to the potent protein synthesis inhibitor cycloheximide terminates in cell death. In the present study we investigated the effect of insulinlike growth factor-1, insulin, and epidermal growth factor on cell death induced by cycloheximide in the confluent MCF-7 cells, and correlated this effect to the inhibition rate of protein synthesis. Cell death was evaluated by measuring either dead cells by the trypan blue dye exclusion test or by the release of lactic dehydrogenase into the culture medium. After 48 h incubation, cycloheximide (10 to 50 micrograms/ml) was shown to induce cell death in a concentration-dependent manner. Insulinlike growth factor-1, at physiologic concentrations (0.2 to 5 ng/ml), reduced this cell death. Insulin at supraphysiologic concentrations (1 to 10 micrograms/ml) mimicked the effect of insulinlike growth factor-1, whereas epidermal growth factor (10 to 50 ng/ml) had no effect. More than 90% of protein synthesis measured by [3H]leucine incorporation was inhibited by 10 to 50 micrograms/ml cycloheximide. Insulinlike growth factor-1 and insulin at the concentrations that reduced cell death to control level, had no effect on the protein synthesis inhibition rate induced by cycloheximide. These results indicate that inhibition of cell death by insulinlike growth factor-1 does not depend on protein synthesis and may be mediated via a posttranslational modification effect.

Previously we have shown that IGF-I protected MCF-7 cells against death induced by the protein synthesis inhibitor cycloheximide (CHX). In the present study we investigated the ability of protein kinase C activator 12-0-tetradecanoyl-phorbol-13-acetate (TPA), the protein kinase A activator 8-bromoadenosine 3'5'-cyclic monophosphate (Br-cAMP), and the enzyme inhibitor aurintricarboxylic acid (ATA) to protect MCF-7 cells against death, due to a continuous presence of CHX. Cell death was evaluated after 48 h of incubation by several techniques (trypan blue staining, release of lactic dehydrogenase, cellular ATP content, transmission electron microscopy, and DNA fragmentation). Apoptosis which terminates in necrosis, characterized this mode of cell death. TPA and ATA at optimal concentrations of 40 ng/ml and 100 micrograms/ml, respectively, reduced cell death to the control level (without CHX), while Br-cAMP at an optimal concentration of 650 micrograms/ml reduced cell death only partially. IGF-1, TPA, and ATA, which stimulated protein synthesis in the control MCF-7 cells, had no effect on protein synthesis in the CHX-treated cells, indicating that the survival effect is not due to new protein synthesis. The protein kinase C inhibitor staurosporine blocked the survival effect of TPA and IGF-1 in a dose-dependent manner, however did not affect the survival effect of ATA. The tyrosine kinase inhibitor genistein blocked the survival effect of IGF-1, but not that of TPA and ATA. Our results provide evidence for several distinctive pathways, the activation of which protects MCF-7 cells against death, due to protein synthesis inhibition.

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