The cytostatic effects of alpha-interferon may be mediated by transforming growth factor-beta

Role of transforming growth factor beta in the growth inhibition of human breast cancer cells by basic fibroblast growth factor

Recent studies from our laboratory have revealed that basic fibroblast growth factor (bFGF) selectively inhibits the proliferation of human MCF-7 breast cancer cells. It has also been shown to enhance cis-platinum-induced apoptosis, decrease levels of the anti-apoptotic gene product bcl-2, and increase levels of the cyclin-dependent protein kinase inhibitor p21/WAF1/Cip1. Transforming growth factor beta-1 (TGFbeta1), a cell growth regulator has been found to have an inhibitory effect on breast cancer cells. The aim of the present study was to evaluate the possible role of TGFbeta1 in the antiproliferative effects of bFGF in MCF-7 breast cancer cells. We found that exogenous, as well as endogenous (overexpressed) bFGF increased TGFbeta1 mRNA expression in the cells and enhanced the secretion of TGFbeta1 into culture medium. However, exogenous addition of TGFbeta1 neither led to a decrease in bcl-2 nor induced an increase in the levels of p21/WAF1/Cip1 and neutralizing antibodies to TGFbeta1, did not reverse bFGF-induced G1 arrest northe increase in p21/WAF1/Cip1 level. In contrast, antisense oligonucleotides to TGFbeta1 abrogated the antiproliferative effects and inhibited the induction of p21/WAF1/Cip1 by bFGF in MCF-7 cells. These data suggest that the anti-proliferative effects of bFGF in human MCF-7 breast cancer cells are mediated by endogenous TGFbeta1, while exogenous TGFbeta1 does not mimic all the effects of bFGF on these breast cancer cells. These findings provide an important basis for further investigations into the autocrine and paracrine processes that control the growth of breast cancer cells.

Minimal residual disease in metastatic breast cancer: treatment with IFN-beta, retinoids, and tamoxifen

The aim of this pilot study was to investigate if chemotherapy (CT) followed by the combination of interferon-beta (IFN-beta), retinoids, and tamoxifen could be effective in the treatment of metastatic breast cancer (MBC). Thirty-six patients with stage IV carcinoma of the breast were treated with six courses of cyclophosphamide, 5-fluorouracil, 4-epidoxorubicin, vincristine, and prednisone every 3 weeks (FECPV), followed by two courses of non-cross-resistant drugs, methotrexate, mitomycin C, and mitoxantrone (MMM). Treatment was continued, in responders, with low dose IFN-beta, retinyl palmitate, and tamoxifen until relapse of the disease occurred. Among 36 evaluable patients, 23 achieved a clinical response (64 %) (95 % confidence interval [c.i.] 46 %-79 %), 7 had stable disease (19%), and 6 (17%) progressed. Leukopenia occurred in 15 patients, thrombocytopenia in 6, and anemia in 11. Sixteen patients had nausea/vomiting, stomatitis was observed in 9, and diarrhea occurred in 3. Toxicity from maintenance therapy was mild and mainly hepatic. Median response duration was 31 months (range 5-107). Median overall survival was 32 months (9-108). Our study shows that this combined approach for the treatment of MBC is feasible, with an acceptable toxicity.

Effects of tamoxifen and interferon-beta or the combination on tumor-induced angiogenesis

Inhibition of angiogenesis by anti-tumor agents may play a role in tumor growth arrest. Tamoxifen and interferon-alpha/beta (IFN-alpha/beta) exhibit potentiated anti-proliferative activity against tumor cells. However, additional host-mediated effects such as modulation of angiogenesis may also inhibit tumor growth in vivo. The effect of tamoxifen and IFN-beta on angiogenesis induced by 2 human tumors, MCF-7 breast carcinoma (estradiol dependent) and NIH-OVCAR-3 ovarian carcinoma (estradiol independent), was assessed. Treatment of nude mice bearing MCF-7 tumors with tamoxifen resulted in a 68% decrease in the number of vessels at the tumor periphery. Treatment with IFN-beta yielded a 33% reduction. Treatment of nude mice bearing NIH-OVCAR-3 tumors with tamoxifen resulted in a 73% decrease in the number of vessels. Treatment with IFN-beta yielded a 57% reduction. Combination treatment resulted in augmented anti-angiogenic effects. As single agents, both tamoxifen and IFN-beta inhibited xenograft tumor growth. Ten weeks of tamoxifen treatment resulted in growth inhibition of MCF-7 and NIH-OVCAR-3 carcinomas by 85% and 66%, respectively. Ten weeks of IFN-beta treatment resulted in inhibition of growth of MCF-7 and NIH-OVCAR-3 carcinomas by 67% and 88%, respectively. The combination of tamoxifen and IFN-beta completely prevented growth of MCF-7 and NIH-OVCAR-3 carcinomas. The anti-angiogenic effects of tamoxifen and IFN-beta were additive. Inhibition of angiogenesis was detectable before measurable effects on tumor volume in both MCF-7 and NIH-OVCAR-3 tumors. Potentiation of anti-angiogenic effects by tamoxifen and IFN-beta, possibly resulting from enhanced IFN-induced gene expression, may contribute to anti-tumor activity in both estradiol-dependent and estradiol-independent tumors in vivo.

Tamoxifen enhances interferon-regulated gene expression in breast cancer cells

The molecular basis for the enhanced growth inhibition of MCF-7 human breast cancer xenografts by a combination of human interferon-beta (IFN-beta) and tamoxifen was investigated. Treatment of MCF-7, MDA-MB-231, and BT-20 cells with the combination of IFN-beta and tamoxifen resulted in enhanced antiproliferative effects in vitro. Treatment with the combination of IFN-beta and tamoxifen enhanced the expression of several IFN-beta-inducible genes in human breast carcinoma cell lines relative to levels induced by IFN-beta alone. Tamoxifen alone did not induce transcription of IFN-stimulated genes (ISGs). Augmentation of ISG expression by the combination of IFN-beta and tamoxifen was noted in breast tumor cell lines irrespective of their functional estrogen receptor (ER) status or their dependence on estradiol for growth, suggesting that upregulation of ISGs was independent of ER status. Enhancement of IFN-stimulated gene expression by tamoxifen occurred at the transcriptional level. Expression of transfected reporter genes under the control of IFN-alpha/beta regulated promoters was also enhanced in IFN-beta and tamoxifen-treated cells. Similarly, transcriptional induction of chimeric reporter plasmids driven by an IFN-gamma inducible promoter (GAS; IFN-gamma activated site) was also enhanced by the combination of IFN-gamma and tamoxifen. In tamoxifen treated cells, IFN-beta and IFN-gamma readily activated transcription factors ISGF-3 and GAF, respectively. Therefore, augmentation of ISG expression by tamoxifen is an early event in the antitumoral activity of this drug combination.

Steroid-growth factor interaction in human prostate cancer. 1. Short-term effects of transforming growth factors on growth of human prostate cancer cells

In order to better define potential mechanisms of growth regulation in human prostate cancer cells, we have compared biological responses (such as short-term response to both transforming growth factor alpha and beta; TFG alpha and TFG beta) in relation to hormone sensitivity of LNCaP, DU145, and PC3 cells. Androgen receptor (AR) and epidermal growth factor receptor (EGF-R) content of each cell line was also investigated. In addition, expression of EGF, TGF alpha, and TGF beta was evaluated through immunofluorescent staining. Growth of androgen non-responsive PC3 cells was stimulated by TGF alpha (about 35%) and inhibited by TGF beta (more than 50%), with respect to controls, after 48 h exposure. Conversely, AR-positive, hormone-responsive LNCaP cells proved to be poorly sensitive, at least short-term, to either growth factor. Furthermore, high levels of both EGF-R and TGF alpha, and a fairly high amount of EGF, were found in DU145 cells and, to a lesser extent, in LNCaP cells; in contrast, PC3 cells exhibited low expression levels of both receptors (EGF-R) and ligands (EGF, TGF alpha), but displayed remarkable TGF beta binding and relatively high levels of endogenous TGF beta. Overall, these results suggest a differential sensitivity to TGF alpha and TGF beta by prostate cancer cells; TGF alpha response seems not to be proportional to the EGF-R content of individual cell lines.

Quercetin enhances transforming growth factor beta 1 secretion by human ovarian cancer cells

Our study demonstrates that quercetin (Q)-induced growth-inhibitory activity in ovarian cancer cells may be mediated by modulation of transforming growth factor beta 1 (TGF beta 1) production. We used the OVCA 433 cell line which is very sensitive to the anti-proliferative effect of Q and expresses high-affinity, low-capacity TGF beta 1 receptors. Conditioned medium (CM) from Q-treated cells is able to displace 125I-TGF beta 1 from binding to its receptor; moreover Q (10 microM) increases TGF beta 1 activity in CM in a time-dependent fashion starting after 4 hr and reaching a maximum by 24 hr of Q treatment. Q-induced growth inhibition is reversed by a neutralizing anti-TGF beta 1 MAb both in OVCA 433 and in a clonogenic assay of cells from a primary ovarian tumor. Q-induced increase of TGF beta 1 activity in CM is specific since other anti-proliferative compounds, such as Dexamethasone, which is as active on the cell cycle as Q, had no effect on TGF beta 1 secretion. Northern-blot analysis of TGF beta 1 mRNA levels at various times of Q (10 microM) exposure revealed that there was no increase, suggesting that regulation of TGF beta 1 occurs at posttranscriptional levels.

Interferon treatment enhances the expression of underphosphorylated (biologically-active) retinoblastoma protein in human papilloma virus-infected cells through the inhibitory TGF beta 1/IFN beta cytokine pathway

Interferons (IFN) regulate transcription of certain genes playing a role in cell proliferation. Targets of IFN action may include tumor suppressor genes such as the retinoblastoma (RB) gene and cytokines such as transforming growth factor beta 1 (TGF beta 1) and IFN beta which are inhibitors of epithelial cell proliferation. Using reverse transcription followed by PCR amplification, an increase of those growth inhibitory gene mRNA levels (TGF beta 1, IFN beta and RB) were found after interferon treatment in condylomas harboring non-oncogenic human papilloma virus (HPV 6/11) types, in an oncogenic HPV 16-containing cell line, and in a HPV negative, epidermoid carcinoma cell line. In addition, immunodetection by Western blot demonstrated a higher proportion of underphosphorylated (active form) retinoblastoma gene protein (pRB) after IFN treatment due to the decrease in the phosphorylating cdc2 kinase levels. Changes in the phosphorylation pattern of pRB together with the increased expression of those inhibitory genes represent a growth inhibited state in those cells as demonstrated by diminished c-myc expression. Since the extent of c-myc inhibition was significantly lower in the case of oncogenic HPV infection, a role of viral oncoproteins in abrogation of the antiproliferative effect of IFN therapy could be considered. These results demonstrate a new mechanism via which IFNs exert their antiproliferative effect on HPV-infected cells by affecting the expression and phosphorylation of the RB tumor suppressor gene, through the inhibitory TGF beta 1/IFN beta cytokine pathway.

Induction of phenotypic changes in SCLC cell lines in vitro by hexamethylene bisacetamide, sodium butyrate, and cyclic AMP

BACKGROUND

Hexamethylene bisacetamide (HMBA), sodium butyrate (NaBt), and cyclic AMP (cAMP) have been shown to induce differentiation, which may regulate tumour growth differently from conventional cytotoxic drugs. It was the intention in the present study to determine whether alterations could be induced in the phenotype of small cell lung cancer (SCLC) cell lines with HMBA, NaBt and cAMP, and whether these alterations would correlate with reduced growth in vivo, implying a phenotypic shift from malignancy towards differentiation.

MATERIALS AND METHODS

The cell lines were NCI-H69, H187 and H128. The activity of dopa decarboxylase (DDC), the BB isozyme of creatine kinase (CK-BB), the synthesis of bombesin-like peptide (BLI), and the presence of neurone specific enolase (NSE) and chromogranin were used as markers of the small cell phenotype. Clonogenicity in suspension in agar, and growth as xenografts in nude mice, were used as malignancy-associated properties. Cell proliferation in vitro was determined by cell counting and growth curve analysis.

RESULTS

HMBA, NaBt and cAMP were found to be reversibly cytostatic in liquid culture and pre-exposure reduced the cloning efficiency in agar by 60%-80%. Growth as xenografts was inhibited (three- to five-fold increase in the tumour doubling time), most significantly by NaBt. Effects of phenotypic markers were more complex. The most significant were a two-fold reduction in DDC with NaBt and HMBA, a 50% increase in CK-BB with cAMP, and a 70%-100% increase in secreted BLI with HMBA and cAMP, in NCI-H69 cells. No significant effects were seen on NSE and chromogranin. There was little sign of an interaction with adriamycin and vincristine, although a slight increase was observed in the ID50 of VP-16 following treatment with cAMP.

CONCLUSIONS

NaBt, HMBA and cAMP were cytostatic and inhibited tumour growth, but there was no coordinated response in marker expression that would confirm phenotypic alteration indicative of differentiation. The problem of defining differentiation in SCLC further complicated the analysis. The possibility remains of combining these agents with conventional cytotoxics as there appears to be little antagonistic effect, and other studies have suggested synergism may be possible with correct scheduling.

Human recombinant interferon-beta SER and tamoxifen: growth suppressive effects for the human breast carcinoma MCF-7 grown in the athymic mouse

Tamoxifen is the endocrine treatment of choice for breast cancer. However, resistance to therapy and patient relapse inevitably occurs. In future treatment schedules, interferons could be administered with tamoxifen, in an attempt to prevent disease recurrence. Human recombinant interferon-beta SER (rIFN-beta SER) inhibited the growth in vitro of the estrogen receptor (ER) positive breast cancer cell line MCF-7 and the ER negative breast cancer cell line MDA-MB-231. This inhibitory effect was achieved at doses of 50 U/ml and above. The growth of MCF-7 tumors in estradiol-stimulated athymic mice was greatly inhibited by high dose rIFN-beta SER treatment (10(6)U/day). In spite of the impressive antitumor effects upon MCF-7 tumors, rIFN-beta SER had no effect upon ER levels within the tumors at either the RNA or protein level, as measured by Northern blotting and ER-EIA respectively. High dose rIFN-beta SER (10(6)U/day) did result in some inhibition in the growth in vivo of the tamoxifen-stimulated MCF-7 variant MCF-7 TAM, although not to the same extent as was observed with the estradiol-stimulated MCF-7 tumors. rIFN-beta SER was also administered to animals bearing MCF-7 tumors and treated with estradiol and tamoxifen. In the animals undergoing high dose therapy (10(6)U/day), tumor growth was completely suppressed. Furthermore, tumor growth continued to be suppressed in those animals in which the rIFN-beta SER therapy was halted and the tamoxifen capsule removed. No tumors were observed in spite of the environment of estradiol stimulation. Thus, the combination of interferon and tamoxifen was totally growth suppressive for MCF-7 xenografts in nude mice.

Steroid receptor enhancement by natural interferon-beta in advanced breast cancer

In the current study we investigated the effect of two different doses of natural interferon-beta (IFN-beta) on steroid hormone receptors in 45 patients with advanced breast cancer. IFN-beta seems to regulate the receptor mechanisms, inducing in cutaneous metastases an increase of oestrogen and progesterone receptors. Moreover, using IFN-beta and tamoxifen as a combined therapy in 23 receptor-positive patients, no negative interference of the two drugs was observed and no relevant side-effects due to the treatment were noticed. The modulation of steroid receptor content by IFN-beta in advanced breast cancer might represent an interesting way to ameliorate the clinical responsiveness to anti-oestrogens.

The inhibitory effects of interferon gamma on the growth of bladder cancer cells

The inhibitory effect of interferon-gamma on the growth of three human bladder cancer cell lines, RT4, RT112 and MGH-U1, representing tumour grades 1, 2 and 3 respectively, was studied. The effects of 10, 100 and 1000 Uml.-1 of interferon-gamma on cell numbers and thymidine incorporation were measured at 24 hour intervals up to a maximum of seven days. Morphological appearances were also studied. Each line was susceptible to the growth inhibitory effects of interferon-gamma and this was both dose and time dependent. The effects of interferon-gamma, on the RT4 and RT112 cells were apparent from 24 hours, and were both cytostatic and cytotoxic in nature, whereas the effects on MGH-U1 cells were seen from 48 hours onwards and were only cytostatic. Cytological changes occurred in all three cell lines, being most pronounced in RT112. The growth of bladder cancer cells was inhibited by interferon-gamma, and in this study high grade tumour cells were least sensitive.

Gene expression in oestrogen-dependent human breast cancer xenograft tumours

Xenograft tumours from an oestrogen-dependent human breast cancer cell line MCF-7 have been established and characterised in thymectomised, irradiated female CBA strain mice. There was evidence for selection in xenografts of a subpopulation of MCF-7 cells with an altered pattern of gene expression as measured by mRNA levels compared with the original cells in vitro. Tumorigenicity increased significantly on repeated animal passage but oestrogen dependence was retained. Following injection of the mice with oestrogen, mitosis was induced in the tumour cells with associated increases in thymidine uptake and percentage of cells in S-phase. In accord with these changes, c-myc and p53 expression were increased and TGF-beta was suppressed. Thereafter the expression of the c-myc and p53 genes fell whilst that of the TGF-beta gene was induced as the oestrogenic-stimulus declined. The oestrogen-regulated mRNA pS2 showed a biphasic response to oestrogen and levels declined as the serum oestrogen fell to undetectable levels. This xenograft system demonstrates that changes in transcription of oncogenes, growth factor and oestrogen-regulated genes can be detected in vivo in response to oestrogen. It thus provides an in vivo model for studies of the biochemical and molecular basis for therapeutic manipulation of hormone-sensitive human breast cancer.