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Characterization of ret oncogenic activation in MEN2 inherited cancer syndromes
S Xing1, P A Smanik, M J Oglesbee
1Department of Physiology and Internal Medicine, Ohio State University, Columbus 43210, USA.
Abstract:
Germline mutations of c-ret, encoding a receptor-type tyrosine kinase, were found to be associated with variants of multiple endocrine neoplasia type 2 (MEN2A, MEN2B), and familial medullary thyroid carcinoma. NIH/3T3 stable transfectants expressing RET with a mutation of MEN2A (MEN2A/RET) or MEN2B (MEN2B/RET) gained a transformed morphology, formed colonies in soft agar, and formed tumors in nude mice. These results confirmed that both MEN2A/RET and MEN2B/RET exert dominant transforming activities in NIH/3T3 cells. However, in contrast to their clinical manifestation, transfectants expressing MEN2A/RET exhibited a higher tumorigenicity in nude mice than transfectants expressing MEN2B/RET may depend on the presence of its ligand and/or substrates that are absent in NIH/3T3 cells. No change in the cellular localization of the mutated RET proteins was observed compared to c-RET. Interestingly, ret activation in NIT/3T3 cells appeared to be associated with up-regulation of homologous gap-junctional intercellular communication and increased expression of a gap-junctional protein, connexin43.
Insights
Germline mutations in the RET proto-oncogene drive multiple endocrine neoplasia types 2A and 2B. Both MEN2A/RET and MEN2B/RET mutations confer transforming activity, with MEN2A/RET showing higher tumorigenicity in mice.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Germline mutations in the RET proto-oncogene are linked to multiple endocrine neoplasia (MEN) types 2A and 2B, and familial medullary thyroid carcinoma.
- The RET receptor tyrosine kinase plays a crucial role in cellular transformation and tumorigenesis when mutated.
Purpose of the Study:
- To investigate the transforming activities of MEN2A/RET and MEN2B/RET mutations in NIH/3T3 cells.
- To compare the tumorigenicity of MEN2A/RET and MEN2B/RET in vivo.
- To explore the effects of RET activation on cellular communication.
Main Methods:
- Stable NIH/3T3 transfectants expressing MEN2A/RET or MEN2B/RET were generated.
- Cellular morphology, soft agar colony formation, and tumor formation in nude mice were assessed.
- Cellular localization of RET proteins and expression of connexin43 were analyzed.
Main Results:
- Both MEN2A/RET and MEN2B/RET demonstrated dominant transforming activities in NIH/3T3 cells, including anchorage-independent growth and tumor formation.
- Contrary to clinical observations, MEN2A/RET exhibited higher tumorigenicity in nude mice compared to MEN2B/RET.
- RET activation correlated with increased gap-junctional intercellular communication and connexin43 expression.
Conclusions:
- The study confirms the potent transforming capabilities of MEN2A/RET and MEN2B/RET mutations.
- Discrepancies in tumorigenicity between in vitro and in vivo models suggest the involvement of cell-specific factors.
- RET activation influences cellular communication pathways, potentially impacting tumor progression.