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Immunohistochemical analysis of major TGF-beta isoforms and their receptors in laryngeal carcinomas
H Hagedorn1, A Elbertzhagen, I Ruoss
1Department of Otolaryngology, Head and Neck Surgery, University of Munich, Grosshadern Medical Center, Germany.
Abstract:
We analyzed immunohistochemically the tissue distribution of the three major transforming growth factors-beta isoforms (TGF-beta1, -2, -3) and their receptors (TBR-I, -II and -III) in tissue samples from 38 patients with laryngeal squamous cell carcinomas. Besides a qualitative evaluation, the number of the respectively labeled cells was determined by morphometric analysis. In all tumor samples a significant staining of most tumor cells was seen both for the TGF-beta isoforms and the TBRs. Similarly, the majority of stromal cells were labeled. On semiserial sections, there were only minor differences in the distribution pattern and in the number of labeled cells between the three TGF-beta isoforms and the TBRs, suggesting that most tumor cells are actively involved in the neosynthesis of TGF-betas and TBRs; accordingly, at least most tumor cells seem to be capable of producing more than one TGF-beta form and in parallel several TBRs. With decreasing tumor cell differentiation the number of TGF-beta- and TBR-positive tumor cells decreased slightly (but not to a statistically significant degree). Interestingly, the stromal cells were labeled for TGF-betas and TBRs to a lower extent than the epithelial cells, and there was no significant difference between non-tumor-associated control stroma and the immediate peritumoral stroma. Our observations suggest an even, enhanced level of TGF-beta production in laryngeal squamous cell carcinomas, which may explain some well-known side-effects of tumor growth, such as stromal desmoplasia. In addition, the presence of immunoreactive TBR-proteins in the vast majority of tumor cells excludes the mere absence of TBRs in those carcinomas as the cause for inappropriate TGF-beta function in the tumor cells. This in turn suggests that molecular alterations either of the TBR-proteins non-affecting the synthesis and turnover or downstream alterations of the TGF-beta signaling pathway may be main reasons for the loss of response of the tumor cells to the enhanced amounts of TGF-betas.
Insights
Laryngeal squamous cell carcinomas show enhanced production of transforming growth factor-beta (TGF-beta) isoforms and their receptors (TBRs). Molecular alterations, not receptor absence, likely cause tumor cell unresponsiveness to TGF-beta signaling.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Transforming growth factor-beta (TGF-beta) signaling plays a critical role in cell growth, differentiation, and tissue repair.
- Dysregulation of TGF-beta signaling is implicated in various cancers, including laryngeal squamous cell carcinoma (LSCC).
- Understanding the expression patterns of TGF-beta isoforms and their receptors in LSCC is crucial for elucidating tumor progression and therapeutic strategies.
Purpose of the Study:
- To investigate the tissue distribution and expression levels of TGF-beta isoforms (TGF-beta1, -2, -3) and their receptors (TBR-I, -II, -III) in LSCC.
- To correlate the expression of these molecules with tumor cell differentiation.
- To explore the potential mechanisms underlying tumor cell unresponsiveness to TGF-beta in LSCC.
Main Methods:
- Immunohistochemical analysis of tissue samples from 38 LSCC patients.
- Qualitative and quantitative morphometric analysis of TGF-beta isoforms and TBRs expression in tumor and stromal cells.
- Semiserial sectioning to assess co-localization and distribution patterns.
Main Results:
- Significant expression of all TGF-beta isoforms and TBRs was observed in the majority of tumor cells and stromal cells in LSCC samples.
- Tumor cells showed active synthesis of TGF-betas and TBRs, with potential to produce multiple isoforms and receptors.
- Stromal cells exhibited lower expression of TGF-betas and TBRs compared to epithelial cells, with no significant difference between peritumoral and control stroma.
- A slight, non-significant decrease in TGF-beta and TBR-positive tumor cells was noted with decreasing tumor cell differentiation.
- The presence of TBR-proteins in tumor cells suggests that impaired TGF-beta signaling is not due to receptor absence but likely due to downstream molecular alterations.
Conclusions:
- LSCC exhibits an enhanced and even level of TGF-beta production, potentially contributing to stromal desmoplasia.
- The abundance of TBR-proteins in tumor cells indicates that loss of TGF-beta response is not caused by receptor deficiency.
- Altered TGF-beta signaling pathway downstream of the receptors is likely responsible for the tumor cells' unresponsiveness to elevated TGF-beta levels in LSCC.