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Detection of ret homodimers in MEN 2A-associated pheochromocytomas
Abstract:
Using transfection of NIH 3T3 cells, we have recently demonstrated that multiple endocrine neoplasia (MEN) 2A mutations activate the c-Ret protein by inducing its disulfide-linked homodimerization on the cell surface. To investigate whether the homodimers are present in original tumors, the expression of the c-Ret protein was analyzed in eight sporadic and two MEN 2A-associated pheochromocytomas, the latter two of which contained mutations in cysteine 618 or 634 of Ret. The c-Ret protein was expressed at variable levels in all pheochromocytomas examined. By labeling the c-Ret protein immunoprecipitated from tumor tissues with [gamma-32P]ATP in vitro, its homodimers were detected in pheochromocytomas from MEN 2A patients but not in a sporadic tumor. This result represents the first demonstration of Ret homodimers in original tumors.
Insights
Multiple endocrine neoplasia (MEN) 2A mutations activate the c-Ret protein by inducing homodimerization. Ret homodimers were detected in MEN 2A pheochromocytomas, but not sporadic tumors, confirming their presence in original tumors.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Multiple Endocrine Neoplasia (MEN) 2A is a hereditary cancer syndrome.
- Activating mutations in the c-Ret proto-oncogene are implicated in MEN 2A.
- c-Ret protein activation involves disulfide-linked homodimerization.
Purpose of the Study:
- To investigate the presence of c-Ret homodimers in original human pheochromocytoma tumors.
- To determine if c-Ret homodimers are associated with MEN 2A-related pheochromocytomas.
Main Methods:
- Analysis of c-Ret protein expression in eight sporadic and two MEN 2A-associated pheochromocytomas.
- Immunoprecipitation of c-Ret protein from tumor tissues.
- In vitro radioactive labeling of immunoprecipitated c-Ret protein with [gamma-32P]ATP.
Main Results:
- c-Ret protein was expressed in all analyzed pheochromocytomas.
- Ret homodimers were detected in pheochromocytomas from MEN 2A patients.
- No Ret homodimers were found in the sporadic pheochromocytoma examined.
Conclusions:
- This study provides the first evidence of Ret homodimers in original human pheochromocytoma tumors.
- Ret homodimerization is a key mechanism in the pathogenesis of MEN 2A-associated pheochromocytomas.