Acquired Expression of hst-1 in an Autonomous Subline (Chiba Subline 2) Derived from Androgen-responsive Mouse Mammary Tumor (Shionogi Carcinoma 115)

Since growth of Shionogi Carcinoma 115 (SC 115) and its autonomous subline (CS 2) were regulated by fibroblast growth factor-like peptide, expression of int-2 and hst-1 was examined in these cell lines. Hybridization of genomic DNA with long terminal repeat of mouse mammary tumor virus (MMTV) revealed the same pattern of restriction fragments, showing the same integration of MMTV. Although weak expression of int-2 was noticed in the two cells, clear expression of hst-1 was seen only in CS 2 cultured with/without testosterone. It is suggested that autonomous growth of androgen-unresponsive CS 2 is connected with expression of hst-1 .     

Induction of Programmed Death/Apoptosis in Androgen-dependent Mouse Mammary Tumor Cell Line (Shionogi Carcinoma 115) by Androgen Withdrawal

Shionogi Carcinoma 115 (SC 115) cells are a cloned cell line derived from androgen-dependent mouse mammary tumor. They can grow in serum-free culture if a physiological level of androgen is present in the medium, but can not proliferate in culture without testosterone. In the present study, the mechanism of cell death in SC 115 cells after androgen withdrawal was examined . Based upon the temporal sequence of DNA fragmentation, morphologic changes and loss of cell viability, androgen withdrawal induces programmed cell death (apoptosis) of SC 115 cells in serum-free culture. Northern blot analysis was used to identify a series of genes whose expression per cell is enhanced during the recruitment of cells from a nonproliferative (i.e. G₀) state into G₁ (i.e., cyclins Dl and C), from G₁ into the S phase of the cell cycle (i.e., cdk2), and during the programmed cell death pathway (i.e. testosterone repressed prostatic message-2 (TRPM-2), transforming growth factor-β1 (TGF-β1) and glucose regulated 78 kilodalton protein (GRP-78)). Expression of TRPM-2, TGF-β1, GRP-78, and calmodulin genes increases, but that of cyclins C and Dl, and cdk2 genes decreases during programmed cell death of SC 115 cells. These results demonstrate that androgen-dependent SC 115 cells undergo programmed cell death induced by androgen withdrawal, and that this death does not require proliferation or progression into Gi of the proliferative cell cycle. SC 115 cells should be a good model for investigating programmed death of hormone-dependent cancer.     

Progression of Androgen-sensitive Mouse Tumor (Shionogi Carcinoma 115) to Androgen-insensitive Tumor after Long-term Removal of Testosterone

Shionogi Carcinoma 115 (SC115) is an androgen-sensitive transplantable mouse tumor. To study the mode of progression from androgen-sensitive to -insensitive tumor, cloned SC115 cells were serially cultured without androgen. Shortly after withdrawal of androgen, SC115 cells showed markedly decreased growth, but growth resumed gradually with loss of response to androgen and the cells 60 weeks after androgen removal [A(—)60 cells] grew faster than SC115 cells cultured in the presence of androgen. A(—)60 cells showed malignant phenotype with morphological changes and tumorigenicity in male and female mice. Although mRNA and binding capacity of androgen receptor were maintained, the cells after removal of androgen rapidly lost expression of mouse mammary tumor virus-related gene and the loss was irreversible in A(—)60 cells. The stimulating effect of basic flbroblast growth factor (bFGF) temporarily decreased, then recovered to the initial level after long-term androgen removal. This fluctuation of response to bFGF was accompanied with changes in the number of bFGF receptors and amount of bFGF-like substance(s) secreted. The substance(s) seemed to be an FGF-like growth factor different from known factors. It was concluded that progression of SC115 cells to androgen-insensitive ones under an androgen-deprived condition proceeded with adaptation by means of increases in production of an FGF-like growth factor and in binding capacity to this factor.     

Effect of social housing condition on heat shock protein (HSP) expression in the Shionogi mouse mammary carcinoma (SC115)

Our previous studies have shown that social housing conditions can significantly alter the growth rate of the Shionogi mouse mammary carcinoma (SC115). The present study extended our investigations to the molecular level by examining stressor effects on the expression of a group of stress-responsive proteins, the heat shock proteins (HSPs). We hypothesized that HSP expression in SC115 cells may be altered by (a) different social housing conditions in vivo and (b) steroid hormone and growth factor exposure in vitro. Mice were reared in groups (G) or as individuals (I). Immediately following tumor cell injection, mice were rehoused from group to individual (GI), from individual to group (IG), or they remained in groups (GG). Tumor tissue was resected at 0.8 g or 3.0 g, as evidence suggests that tumor size affects HSP expression, which in turn affects proliferation. The data demonstrate that expression of HSP25, 70, and 90 was increased in tumors from mice in the IG compared to GG and GI mice, at both tumor weights examined. In addition, in IG mice, HSP90 expression was greater in 0.8 g compared to 3.0 g tumors. Under controlled culture conditions, hormones known to stimulate SC115 growth both in vivo and in vitro altered HSP expression. Physiological levels of dihydrotestosterone (DHT) and pharmacological levels of hydrocortisone (HC) upregulated expression of HSP25, whereas physiological levels of -estradiol (E₂) upregulated expression of HSP90. These data are the first to demonstrate that a psychosocial stressor, a change in social housing condition, can induce differential HSP expression. Further, these data show that hormones that regulate SC115 tumor growth, also alter HSP expression.     

Inhibitory Effect of a Somatostatin Analogue (SMS 201–995) on the Growth of Androgen-dependent Mouse Mammary Tumor (Shionogi Carcinoma 115)

The influence of a soinatostatin analogue, SMS 201–995 (SMS), on the growth of an androgen-dependent mouse mammary tumor, Shionogi carcinoma 115 (SC115), was studied. Treatment of SC11S tumor-transplanted male mice with s.c. injections of SMS (0.04, 0.2,1, and 5 μg twice a day) resulted in a dose-dependent inhibition of tumor growth. The growth-inhibitory effect of SMS reached its peak at a dose of 1 μg twice a day. SMS was found not to elicit its growth-inhibitory effect through lowering plasma testosterone levels or down-regulating androgen receptor of SC115 tumors. Since specific binding sites for somatostatin were not observed in the membrane fractions of SC115 tumors and SMS did not inhibit the proliferation of primarily cultured SC115 tumor cells, a direct inhibitory mechanism of SMS on SC115 tumors was unlikely to be operative. Since SMS is a very potent inhibitor of growth hormone (GH) secretion, it was speculated that SMS might inhibit the growth of SC115 tumors indirectly through down-regulation of plasma GH levels. This possibility was evaluated by studying the influence of GH replacement on the growth of SC115 tumors grown in SMS-treated mice. GH replacement was done both in a male secretory pattern (intermittent injection, human GH 500 μg/kg twice a day) and in a female secretory pattern (continuous infusion, 1000 μg/kg/day). Intermittent injections of GH fully restored the growth of SC115 tumors in the SMS-treated mice to that in the normal controls but continuous infusion of GH was without effect. These results suggest that SMS inhibits the growth of SC115 tumors through suppression of GH secretion, and that the mode of GH administration is an important determinant of its action on SC115 tumor growth.