p16INK4 gene deletions in childhood acute lymphoblastic leukemias

Inactivation of cyclin-dependent kinase inhibitor genes and development of human acute leukemias

A large body of evidence has definitely demonstrated that cancer development and/or progression is strictly linked to alterations of molecular mechanisms controlling the cell division cycle. In particular, those aberrations which cause a shortening of G1 phase length and a deregulated S phase entry seem to be very important. Two main tumor suppressor loci, involved in the cell cycle regulation, are frequently altered in human tumors. One is located on 13q14 chromosome and includes the gene coding pRb protein while the other is located on 9p21 chromosome and involves two genes, namely p16INK4A and p15INK4B which belong to the same gene family. While RB1 gene is scarcely altered in hematological tumors, the putative tumor suppressor gene(s) on 9p21 appear(s) to be frequently inactivated in some subtypes of cancers derived from hematopoietic tissues. This manuscript will review the main biochemical aspects of the cell division cycle with major emphasis devoted to the findings regarding the recently characterized small proteic mitotic inhibitors and to their possible role in cancer formation. Particular attention will be paid to the data concerning the incidence of p16INK4A (and p15INK4B) gene(s) inactivation in human acute lymphoblastic leukemias. Indeed, such gene(s) seems to be the main, and until now the unique, tumor suppressor gene consistently altered in this acute hematological cancer diseases. Finally, future directions in studies on the connection between cell cycle control and leukemogenesis will be analyzed.

Role of the cyclin-dependent kinase 4 and 6 inhibitor gene family p15, p16, p18 and p19 in leukemia and lymphoma

Neoplastic diseases are proliferative disorders characterized by uncoordinated cell growth. Cellular proliferation follows an orderly progression through the cell cycle, which is governed by different cyclins and cyclin dependent kinases (CDKs). Recently, CDK-inhibitors, which are a new class of small proteins involved in the negative regulation of the cell cycle, have been identified by virtue of their ability to interact physically with cyclin/CDK-complexes. As the genes encoding the CDK4- and CDK6-inhibitors (CDK4/6-inhibitors) p16INK4A/CDKN2/MTS1 and p15INK4B/MTS2 have been found to be altered in many cancer cell lines and primary neoplastic tissues, CDK-inhibitors in general and CDK4/6-inhibitors in particular are now a se: of candidate tumor suppressors. The p15 and p16 genes map to a region frequently deleted in lymphoid neoplasms. Therefore, considerable efforts have been made to determine the role of CDK4/6-inhibitors in hematologic malignancies: This article will review alterations of components of the cell-cycle machinery in brief and summarize the role of the CDK4/6-inhibitors p16INK4A, p15INK4B, p18INK4C and p19INK4D in leukemias and lymphomas.