The association of c-myc rearrangements with specific types of human non-Hodgkin's lymphomas.

The function of c-myc in physiology is only partially known. Its product has DNA binding properties and plays a role in the control of proliferation and differentiation. In general, increased c-myc expression leads to proliferation and abolishment of differentiation. The involvement of c-myc in mouse plasmacytomas and human Burkitt's lymphoma is well known: due to chromosomal translocation c-myc comes under the influence of regulatory elements of immunoglobulin genes, leading to increased expression of the gene and proliferation of the cells. In man, the chromosomal translocations may occur within the increased pool of (pre) B-cells due to Epstein Barr virus (EBV) and malaria infection with subsequent immunosuppression. Apart from these early (primary?) events in lymphomagenesis, c-myc is also often involved in tumour progression, probably by a similar mechanism. Different types of c-myc involvement are associated with specific types of lymphoma: there are differences between endemic, sporadic and ileocecal Burkitt's lymphoma as well as between those and primary extranodal large cell lymphoma and large cell lymphoma which has progressed. These differences are associated with the differentiation of the involved lymphoid cells and may point to the stage of differentiation in which the oncogenic event occurred.