ABSTRACT
Radiation-induced human papillary thyroid carcinomas (PTCs) show a high prevalence of fusions of the RET proto-oncogene to heterologous genes H4 (RET/PTC1) and ELE1 (RET/PTC3), respectively. In contrast to the normal membrane-bound RET protein, aberrant RET fusion proteins are constitutively active oncogenic cytosolic proteins that can lead to malignant transformation of thyroid epithelia. To detect specific tumor-associated protein changes that reflect the effect of RET/PTC fusion proteins, we analyzed normal thyroid tissues, thyroid tumors of the RET/PTC1 and RET/PTC3 type and their respective lymph node metastases by a combination of high-resolution two-dimensional electrophoresis and matrix-assisted laser desorption/ionization-mass spectrometry. PTCs without RET rearrangements served as controls. Several cytoskeletal protein species showed quantitative changes in tumors and lymph node metastases harboring RET/PTC1 or RET/PTC3. We observed prominent C-terminal actin fragments assumedly generated by protease cleavages induced due to enhanced amounts of the active actin-binding protein cofilin-1. In addition, three truncated vimentin species, one of which was proven to be headless, were shown to be highly abundant in tumors and metastases of both RET/PTC types. The observed protein changes are closely connected with the constitutive activation of RET-rearranged oncoproteins and reflect the importance to elucidate disease-related typical signatures on the protein species level.
Subject(s)
Cytoskeletal Proteins/metabolism , Neoplasms, Radiation-Induced/metabolism , Oncogene Proteins, Fusion/metabolism , Proto-Oncogene Proteins c-ret/genetics , Thyroid Neoplasms/metabolism , Adolescent , Carcinoma , Carcinoma, Papillary , Child , Female , Humans , Lymphatic Metastasis , Neoplasms, Radiation-Induced/genetics , Phenotype , Proto-Oncogene Mas , Recombination, Genetic , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Thyroid Cancer, Papillary , Thyroid Neoplasms/genetics , Two-Dimensional Difference Gel Electrophoresis , Young AdultABSTRACT
The proteomic approach is a valuable tool to detect and identify proteins that are associated with cancer. In previous investigations on experimentally induced rat hepatomas, we detected aldose reductase-like protein (ARLP) as a highly significant marker protein. Our present study was intended to look for the presence of similar tumor-associated marker proteins on human hepatocellular carcinomas (HCC). We found several novel tumor-associated protein variants that represent members of the aldo-keto reductase (AKR) superfamily. Human aldose reductase-like protein-1 (hARLP-1) was the most prominent tumor-associated AKR member detected in HCC by 2-dimensional electrophoresis (2-DE) and identified by mass spectrometric fingerprinting. The enzyme was found in 4 distinct forms (hARLP-1, 36/7.4 (kd/pI); hARLP-2, 36/7.2; hARLP-3, 36/6.4; and hARLP-4, 33/7.35). In addition, a human aldose reductase-like protein (hARLP-5, 36/7.6) was identified that differed from hARLP-1 by 1 amino acid (D313N), indicating 2 allelic forms of the human aldose reductase-like gene. A novel antibody directed against common parts of the hARLPs revealed hARLP reactivity in human HCC by immunohistochemistry. Furthermore, aldose reductase (AR) was identified and characterized as a tumor-associated variant. In conclusion, in all investigated human HCCs at least one of the various types of the described tumor-associated proteins of the AKR superfamily was clearly present. Of these HCC samples, 95% were positive for hARLPs as proven by 2-DE analysis and/or by use of the antibody directed against hARLP. Thus, hARLP is a strong candidate for use as an immunohistochemical diagnostic marker of human HCC.
