In addition to the tumor suppressor genes such as Rb and p53, it: has been
found that some molecules of the same class named CKI (cyclin-dependent kin
ase inhibitor) also play an important role in the inhibition of tumorigenes
is and the tumor progression. In the KIP and INK4 families of CKIs, p15 sha
res extensive homology with p16. Findings in many tumors and their cell lin
es show that the inactivation of p15 (deletion, mutation, rearrangement, et
c.) is very frequent, and inactive p15 is involved in the progress of some
tumors. These studies provide evidence that the p15 is a new tumor suppress
or gene. Furthermore, the research on the molecular mechanism of p15 in reg
ulation of cell proliferation shows that p15 can inhibit the growth of some
kinds of tumor cells, and p15 is the mediator of TGF-beta-induced cell arr
est. Investigations on p15 in cell differentiation suggest that increased p
15 is related to the change of malignant phenotype. These results supply cl
ues for further interpretation about the molecular mechanism of cell cycle
control and cell tumorigenesis. And they may provide theoretical and experi
mental basis for application of p15 to clinical therapy of tumors.