R. Oskam

Molecular analysis of the human trk oncogene, a transforming gene isolated from a colon carcinoma biopsy, revealed the existence of a novel member of the tyrosine kinase gene family. This locus, which we now designate the trk proto-oncogene, codes for a protein of 790 amino acid residues that has several features characteristic of cell surface receptors. They include (i) a 32-amino-acid-long putative signal peptide, (ii) an amino-terminal moiety (residues 33 to 407) rich in consensus sites for N-glycosylation, (iii) a transmembrane domain, (iv) a kinase catalytic region highly related to that of other tyrosine kinases, and (v) a very short (15 residue) carboxy-terminal tail. Residues 1 to 392 were absent in the trk oncogene, as they were replaced by tropomyosin sequences. However, no other differences were found between the transforming and nontransforming trk alleles (residues 392 to 790), suggesting that no additional mutations are required to activate the transforming potential of this gene. The human trk proto-oncogene codes for a 140,000-dalton glycoprotein, designated gp140proto-trk. However, its primary translational product is a 110,000-dalton glycoprotein which becomes immediately glycosylated, presumably during its translocation into the endoplasmic reticulum. This molecule, designated gp110proto-trk, is further glycosylated to yield the mature form, gp140proto-trk. Both gp110proto-trk and gp140proto-trk proteins possess in vitro kinase activity specific for tyrosine residues. Finally, iodination of intact NIH 3T3 cells expressing trk proto-oncogene products indicated that only the mature form, gp140proto-trk, cross the plasma membrane, becoming exposed to the outside of the cell. These results indicate that the product of the human trk locus is a novel tyrosine kinase cell surface receptor for an as yet unknown ligand.

Molecular analysis of the human trk oncogene, a transforming gene isolated from a colon carcinoma biopsy, revealed the existence of a novel member of the tyrosine kinase gene family. This locus, which we now designate the trk proto-oncogene, codes for a protein of 790 amino acid residues that has several features characteristic of cell surface receptors. They include (i) a 32-amino-acid-long putative signal peptide, (ii) an amino-terminal moiety (residues 33 to 407) rich in consensus sites for N-glycosylation, (iii) a transmembrane domain, (iv) a kinase catalytic region highly related to that of other tyrosine kinases, and (v) a very short (15 residue) carboxy-terminal tail. Residues 1 to 392 were absent in the trk oncogene, as they were replaced by tropomyosin sequences. However, no other differences were found between the transforming and nontransforming trk alleles (residues 392 to 790), suggesting that no additional mutations are required to activate the transforming potential of this gene. The human trk proto-oncogene codes for a 140,000-dalton glycoprotein, designated gp140proto-trk. However, its primary translational product is a 110,000-dalton glycoprotein which becomes immediately glycosylated, presumably during its translocation into the endoplasmic reticulum. This molecule, designated gp110proto-trk, is further glycosylated to yield the mature form, gp140proto-trk. Both gp110proto-trk and gp140proto-trk proteins possess in vitro kinase activity specific for tyrosine residues. Finally, iodination of intact NIH 3T3 cells expressing trk proto-oncogene products indicated that only the mature form, gp140proto-trk, cross the plasma membrane, becoming exposed to the outside of the cell. These results indicate that the product of the human trk locus is a novel tyrosine kinase cell surface receptor for an as yet unknown ligand.

BACKGROUND: The objective of the current study was to evaluate the response rate, survival, and toxicity of treatment with cisplatin and high dose intravenous continuous infusion interleukin-2 (IL-2) with or without interferon-alpha-2a (IFN) in patients with metastatic melanoma. METHODS: One hundred and seventeen patients with metastatic melanoma randomly were assigned to receive cisplatin, 100 mg/m2, followed after a 3-day rest period by IL-2, 18 x 10(6) IU/m2, on Days 3-6 and Days 17-21 (Arm 1) or cisplatin and IL-2 using an identical schedule plus subcutaneous IFN, 9 x 10(6) U, 3 times a week during IL-2 administration (Arm 2). In the absence of disease progression or undue toxicity, the cycle could be repeated on Day 29. Patients who responded after two cycles eventually could receive a third cycle. One hundred and one patients were evaluable for toxicity and efficacy. RESULTS: On treatment Arm 1, 3 patients (6%) achieved a complete response (CR) and 5 patients (10%) achieved a partial response (PR) with a median response duration of 3.8 months for the CRs and 8.7 months for the PRs. On treatment Arm 2, 2 patients (3%) achieved a CR (durations of 5.9 and 33.1 months, respectively) and 11 patients (21%) a PR with a median response duration of 8.3 months. The median durations of overall survival were 10.4 months (range, 1.1-39.7+ months) and 10.9 months (range, 0.5-38.1+ months) for treatment Arms 1 and 2, respectively. The toxicity profile was consistent with the known side effects of this IL-2 intravenous regimen combined with cisplatin chemotherapy and IFN. Toxicity was more pronounced in treatment Arm 2 compared with treatment Arm 1. There were 2 and 4 patients, respectively, in treatment Arms 1 and 2 who died within 28 days after completion of treatment. CONCLUSIONS: The observed overall response rates of 16% and 25% in treatment Arms 1 and 2, respectively, is lower than that expected with biochemotherapy; despite the fact that the objective of the trial was not to show any difference between the 2 treatment arms, our results indicate that the addition of IFN, at the dose and schedule used in this trial, fails to improve the activity of a cisplatin/IL-2 regimen significantly in patients with metastatic melanoma. Although response rates were relatively low, the median overall survival was nearly 1 year in both groups.