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Myosin isoform expression in rat rhabdomyosarcoma induced by Moloney murine sarcoma virus
Abstract:
Myosin isoform expression was analyzed in experimental rhabdomyosarcoma (RMS) using monoclonal antibodies (mAbs) and immunofluorescence techniques. Tumors induced by inoculating newborn rats with Moloney murine sarcoma virus (Mo-MSV) were examined 30-90 days after birth. Nine tumors and two lymph node metastases were studied by direct, indirect, and double immunofluorescence assays using a panel of five anti-myosin mAbs. The mAb BF-45 was specifically reactive with embryonic myosin heavy chain (MHC), mAb BF-34 was specific for a neonatal MHC epitope, mAb BF-B6 was directed against an epitope present in both embryonic and neonatal MHC, and mAbs BF-F3 and BF-32 detected epitopes present in adult MHC isoforms. Anti-desmin antibodies were also used for comparison. The results of this study show that: (1) the majority of neoplastic cells stained for desmin while only a minority of neoplastic cells were labeled by anti-myosin antibodies; (2) myosin positive tumor cells contained predominantly embryonic and neonatal MHC types but rare RMS cells reacted exclusively with anti-adult myosin antibodies; and (3) adult and embryonic MHC phenotypes were occasionally detected within the same tumor cell especially in RMS with the longest latencies. Together these results would suggest that the mechanism(s) regulating MHC gene expression in skeletal muscle cells can be altered by the transforming activity of Mo-MSV.
Insights
Experimental rhabdomyosarcoma (RMS) shows altered myosin heavy chain (MHC) expression, predominantly featuring embryonic and neonatal types. This suggests Moloney murine sarcoma virus (Mo-MSV) transforms muscle cells, affecting MHC gene regulation.
Area of Science:
- Molecular Biology
- Oncology
- Immunology
Background:
- Rhabdomyosarcoma (RMS) is a pediatric cancer originating from muscle cells.
- Understanding the molecular changes in RMS is crucial for developing targeted therapies.
- Myosin heavy chain (MHC) isoforms are key indicators of muscle cell differentiation and type.
Purpose of the Study:
- To investigate myosin isoform expression in experimental rhabdomyosarcoma (RMS).
- To determine if Moloney murine sarcoma virus (Mo-MSV) affects myosin heavy chain (MHC) gene expression in developing tumors.
- To compare myosin expression profiles with desmin expression in RMS.
Main Methods:
- Experimental rhabdomyosarcoma (RMS) was induced in newborn rats using Moloney murine sarcoma virus (Mo-MSV).
- Monoclonal antibodies (mAbs) specific for different myosin heavy chain (MHC) isoforms (embryonic, neonatal, adult) were used.
- Immunofluorescence techniques, including direct, indirect, and double assays, were employed to analyze myosin expression in tumor tissues.
- Anti-desmin antibodies were used for comparative analysis.
Main Results:
- The majority of neoplastic cells in RMS tumors expressed desmin.
- A minority of RMS cells showed reactivity with anti-myosin antibodies, predominantly expressing embryonic and neonatal MHC types.
- Rare RMS cells expressed adult MHC isoforms, and some tumor cells co-expressed adult and embryonic MHC phenotypes, particularly in tumors with longer latency.
- Myosin expression was analyzed in nine tumors and two lymph node metastases.
Conclusions:
- The expression of myosin heavy chain (MHC) isoforms is altered in experimental rhabdomyosarcoma (RMS).
- The transforming activity of Moloney murine sarcoma virus (Mo-MSV) appears to dysregulate MHC gene expression in skeletal muscle cells.
- These findings suggest a potential link between viral transformation and aberrant muscle-specific gene expression in RMS development.