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c-myc, c-fos, and c-myb gene expression in human pituitary adenomas
M Woloschak1, J L Roberts, K Post
1Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, New York, New York 10029.
Abstract:
The possible roles of certain oncogenes in the development of pituitary tumors has not been investigated. We have examined the expression of c-myc, c-fos, and c-myb in a number of human pituitary tumors by ribonuclease protection assays, as these oncogenes have been implicated to have roles in the pathogenesis of other human tumors (12, 13, 15, 16). In several tumors examined (9 of 30) c-myc was expressed at levels 4-9 times greater than the level detected in normal postmortem pituitary. Although a larger percentage of negative immunohistochemical-staining tumors overexpressed c-myc, c-myc over-expression was not limited to this group of tumors. c-Fos was overexpressed in 1 of 30 tumors examined at a level 5.8-fold higher than that detected in normal postmortem pituitary. This tumor stained positive for ACTH by immunohistochemistry and was considered highly aggressive, demonstrating invasion beyond the sella turcica; however, when other ACTH-staining and invasive pituitary tumors were examined, no abnormality in the expression of c-fos was detected. In 30 tumors, c-myb was expressed at approximately the same level as that detected in normal postmortem pituitary. We conclude that c-myc is overexpressed in a subgroup of pituitary tumors and that this overexpression occurs broadly among the different groups of immunohistochemical-staining tumors. c-Fos overexpression appears to be much less common in pituitary tumors and does not necessarily correlate with the ability of the tumor to become invasive. c-Myb does not appear to have a role in the pathogenesis of pituitary tumors.
Insights
This study investigated oncogene expression in pituitary tumors, finding c-myc overexpression in a subset of tumors. c-Fos and c-myb showed no significant alterations, suggesting limited roles in pituitary tumor development.
Area of Science:
- Oncology
- Molecular Biology
- Endocrinology
Background:
- The role of oncogenes in pituitary tumor development remains largely unexplored.
- Oncogenes like c-myc, c-fos, and c-myb are implicated in other human cancers.
Purpose of the Study:
- To investigate the expression levels of c-myc, c-fos, and c-myb in human pituitary tumors.
- To determine if these oncogenes are associated with pituitary tumor pathogenesis or aggressiveness.
Main Methods:
- Ribonuclease protection assays were used to quantify oncogene expression.
- Human pituitary tumors (30 samples) and normal postmortem pituitary tissue were analyzed.
- Immunohistochemistry was employed to assess tumor characteristics.
Main Results:
- c-myc was overexpressed (4-9 fold) in 9 of 30 pituitary tumors, irrespective of immunohistochemical staining.
- c-Fos overexpression (5.8 fold) was observed in only one aggressive, ACTH-positive pituitary tumor, but not consistently in other aggressive tumors.
- c-myb expression levels were comparable to normal pituitary tissue across all samples.
Conclusions:
- c-myc overexpression is present in a subgroup of pituitary tumors and occurs across various tumor types.
- c-Fos overexpression is rare in pituitary tumors and does not correlate with invasiveness.
- c-myb does not appear to play a significant role in the pathogenesis of pituitary tumors.