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5'-Deoxy-5'-methylthioadenosine phosphorylase and p16INK4 deficiency in multiple tumor cell lines
F Della Ragione1, G Russo, A Oliva
1Institute of Biochemistry of Macromolecules, Medical School, Second University of Naples, Italy.
Abstract:
5'-Deoxy-5'methylthioadenosine phosphorylase (MTA-Pase) gene is localized at the 9p21 region linked to the recently identified putative tumor suppressor gene, p16INK4, which appears implicated in the control of cell division cycle. The phosphorylase is a housekeeping enzyme involved in the purine and amino acid metabolism whose activity is evidentiable in all the normal tissues. Chromosomal deletions encompassing both MTAPase and p16INK4 genes cause the total absence of the enzymatic activity only in malignant cells, thus resulting in defined metabolic differences between malignant and normal cells. MTAPase deficiency was investigated by direct radiochemical assay method and by immunochemical techniques in 35 different human malignant cell lines established from several tumor types. The enzyme-deficient cells derived from breast, lung, ovary and liver cancer, malignant melanomas, malignant gliomas and liposarcomas. Two of the MTAPase-deficient cell preparations (from a liver carcinoma and from a melanoma) are primary cultures thus directly representing the original cancer genotypes. Several of the MTAPase-negative cells were studied for p16INK4 gene deletions and for p16INK4 protein deficiency. In all the examined samples a full correlation exists between the lack of MTAPase and that of p16INK4. A similar result was obtained analysing extracts of Vero cell line, which is a fibroblast MTAPase-negative cell line established from the kidney of a normal adult monkey. Conversely, Cos cells, which also are fibroblasts derived from monkey kidney, show both MTAPase and p16INK4 protein. These results: (i) demonstrate that the phosphorylase deficiency is distributed among almost all the most important human cancers; (ii) confirm and extend the tumor types were p16INK4 gene inactivation is observable and (iii) suggest that deletions at 9p21 (in humans) or at syntenic chromosomes (in other species) might represent a general mechanism of p16INK4 gene loss of function and possibly, in turn, of cancer development and/or progression.
Insights
5'-Deoxy-5'methylthioadenosine phosphorylase (MTA-Pase) deficiency is observed in most human cancers, correlating with p16INK4 tumor suppressor gene loss. This suggests 9p21 deletions are a common mechanism in cancer development.
Area of Science:
- Oncology
- Biochemistry
- Genetics
Background:
- 5 '-Deoxy-5'methylthioadenosine phosphorylase (MTA-Pase) is a housekeeping enzyme involved in purine and amino acid metabolism, present in normal tissues.
- The MTA-Pase gene is located at 9p21, near the p16INK4 tumor suppressor gene, which regulates the cell division cycle.
- Malignant cells often exhibit chromosomal deletions affecting both MTA-Pase and p16INK4 genes, leading to enzyme deficiency and metabolic differences.
Purpose of the Study:
- To investigate MTA-Pase deficiency in various human malignant cell lines.
- To determine the correlation between MTA-Pase deficiency and p16INK4 gene/protein status.
- To explore the role of 9p21 deletions in cancer development.
Main Methods:
- Radiochemical and immunochemical assays were used to detect MTA-Pase activity.
- Analysis of p16INK4 gene deletions and protein deficiency in MTA-Pase-negative cell lines.
- Examination of cell lines from diverse human tumor types, including primary cultures.
Main Results:
- MTA-Pase deficiency was identified in 35 human malignant cell lines from breast, lung, ovary, liver cancers, melanomas, gliomas, and liposarcomas.
- A complete correlation was found between MTA-Pase deficiency and p16INK4 gene deletion/protein deficiency across all examined samples.
- Vero cells (MTAPase-negative) showed p16INK4 deficiency, while Cos cells (MTAPase-positive) retained p16INK4.
Conclusions:
- MTA-Pase deficiency is prevalent in a wide range of human cancers.
- The findings confirm and expand the spectrum of tumors associated with p16INK4 inactivation.
- 9p21 deletions represent a potential general mechanism for p16INK4 loss of function, contributing to cancer development and progression.