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Inhibition of proliferation and induction of apoptosis in soft tissue sarcoma cells by interferon-alpha and retinoids
T Brodowicz1, C Wiltschke, D Kandioler-Eckersberger
1Clinical Division of Oncology, Department of Medicine I, University Hospital, Vienna, Australia.
Abstract:
Uncontrolled proliferation and a defect of apoptosis constitute crucial elements in the development and progression of tumours. Among many other biological response modifiers known to influence these mechanisms, the efficacy of retinoids and interferons in the treatment of various malignant entities is currently matter of discussion. In the present study, we have investigated the effects of 9-cis-retinoic acid (9cRA), 13-cis-retinoic acid (13cRA), all-trans-retinoic acid (tRA) and interferon-alpha on proliferation and apoptosis of human soft tissue sarcoma (STS) cell lines HTB-82 (rhabdomyosarcoma), HTB-91 (fibrosarcoma), HTB-92 (liposarcoma), HTB-93 (synovial sarcoma) and HTB-94 (chondrosarcoma) in relation to p53 genotype as well as p53 expression. HTB-91, HTB-92 and HTB-94 STS cells exhibited mutant p53, whereas wild-type p53 was found in HTB-93 STS cells, and a normal p53 status in HTB-82 STS cells, carrying a silent point mutation only. Interferon-alpha, irrespective of p53 status, inhibited the proliferation of all five cell lines dose- and time-dependently. Similarly, 9cRA, 13cRA and tRA decreased the proliferation of HTB-82 and HTB-93 STS cells, whereas the proliferation of p53-mutated HTB-91, HTB-92 and HTB-94 STS cells remained unchanged. Furthermore, only 9cRA and tRA were capable of inducing apoptosis in HTB-82 and HTB-93 STS cells, whereas HTB-91, HTB-92 and HTB-94 STS cells did not undergo apoptosis under the influence of 9cRA or tRA. Retinoic acid receptor (RAR)-alpha and RAR-beta mRNA were not detectable by Northern blot analysis in the five STS cell lines, whereas mRNA for the universal retinoic acid receptor, RAR-gamma, was expressed in all STS cell lines indicating that retinoid resistance was not associated with a lack of RAR expression. Apoptosis was not induced by interferon-alpha or 13cRA in any of the five STS cell lines tested. Our results indicate that within the panel of tested STS cell lines, inhibition of proliferation and induction of apoptosis result from different mechanisms which differ in their dependence upon the presence of intact p53.
Insights
Retinoids and interferons affect soft tissue sarcoma (STS) cell proliferation and apoptosis differently. Interferon-alpha inhibited all STS cell lines, while retinoids like 9-cis-retinoic acid (9cRA) and all-trans-retinoic acid (tRA) induced apoptosis only in cells with intact p53.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Uncontrolled cell proliferation and defective apoptosis are hallmarks of cancer.
- Retinoids and interferons are biological response modifiers with potential anti-cancer effects.
- Their efficacy in treating malignancies, including soft tissue sarcoma (STS), is under investigation.
Purpose of the Study:
- To investigate the effects of 9-cis-retinoic acid (9cRA), 13-cis-retinoic acid (13cRA), all-trans-retinoic acid (tRA), and interferon-alpha on STS cell proliferation and apoptosis.
- To correlate these effects with the p53 genotype and expression in various human STS cell lines.
Main Methods:
- Treatment of five human STS cell lines (HTB-82, HTB-91, HTB-92, HTB-93, HTB-94) with retinoids (9cRA, 13cRA, tRA) and interferon-alpha.
- Assessment of cell proliferation and apoptosis.
- Analysis of p53 genotype and expression.
- Detection of retinoic acid receptor (RAR) mRNA expression via Northern blot.
Main Results:
- Interferon-alpha inhibited proliferation in all tested STS cell lines, regardless of p53 status.
- 9cRA, 13cRA, and tRA reduced proliferation in STS cells with wild-type or normal p53 (HTB-82, HTB-93), but not in p53-mutated cells (HTB-91, HTB-92, HTB-94).
- Apoptosis was induced by 9cRA and tRA only in STS cells with intact p53 (HTB-82, HTB-93); interferon-alpha and 13cRA did not induce apoptosis in any cell line. All cell lines expressed RAR-gamma mRNA.
Conclusions:
- Inhibition of STS cell proliferation and induction of apoptosis by retinoids and interferons involve distinct mechanisms.
- The p53 status is critical for retinoid-induced apoptosis but not for interferon-alpha-mediated proliferation inhibition.
- Retinoid resistance in some STS cell lines is not due to a lack of RAR expression, as RAR-gamma is universally present.