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National Institutes of Health Intramural funds and St Baldrick's Foundation.

No abstract

The ectodomains of numerous proteins are released from cells by proteolysis to yield soluble intercellular regulators. The responsible protease, tumor necrosis factor-alpha converting enzyme (TACE), has been identified only in the case when tumor necrosis factor-alpha (TNFalpha) is released. Analyses of cells lacking this metalloproteinase-disintegrin revealed an expanded role for TACE in the processing of other cell surface proteins, including a TNF receptor, the L-selectin adhesion molecule, and transforming growth factor-alpha (TGFalpha). The phenotype of mice lacking TACE suggests an essential role for soluble TGFalpha in normal development and emphasizes the importance of protein ectodomain shedding in vivo.

Loss of heterozygosity on chromosome 9p21 is one of the most frequent genetic alterations identified in human cancer. The rate of point mutations of p16, a candidate suppressor gene of this area, is low in most primary tumours with allelic loss of 9p21. Monosomic cell lines with structurally unaltered p16 show methylation of the 5' CpG island of p16. This distinct methylation pattern was associated with a complete transcriptional block that was reversible upon treatment with 5-deoxyazacytidine. Moreover, de novo methylation of the 5' CpG island of p16 was also found in approximately 20% of different primary neoplasms, but not in normal tissues, potentially representing a common pathway of tumour suppressor gene inactivation in human cancers.