African Environmental Pressures and Carcinogenesis: The Impact on The Lymphomas, the Leukemias, and Breast cancer

Abstract

The African environment has for millennia been dominated by rampant agents of infections, of which malaria is among the best known, virtually uncontrolled, and associated with lifelong human struggles, ameliorarated by measures as socioeconomicaly affordable. This has led to the emergence of a variety of genetic aberrations, some of which are deleterious, resulting in major disease dysparities, including benign ones like sickle cell disease, and malignancies like the leukaemias, lymphomas, and breast cancer. They include the reduced incidence and the absence of its peak in acute lymphoblastic leukaemia in the first quinquennium of Nigerian children, which is otherwise typically seen in the children of high-income countries. Conversely is the observation in acute myelogenous leukaemia, with its chloroma-associated variant and its incidence peaking in the second quinquennium. This epidemiology is akin to the recent observation of acute myelogenous leukemia among sickle cell disease patients among the people of African descent in California, USA. Chloroma-associated acute myelogenous leukemia, and Burkitt lymphoma are linked with low socioeconomic status, an epidemiological feature that is shared with triple negative breast cancer patients in West Africa and the women of African descent in the United States. While a role for the malaria-associated genetic aberration underlying the Duffy null genotype is confirmed in the diversity of the triple negative breast cancer in the women of West Africa and those of African descent in the United States, it is conceivable, but not yet established in acute myelogenous leukemia. The zoonosis-linked human T-cell lymphotropic virus type 1 infection is associated with at least 17% of non-BL-non-Hodgkin lymphoma in form of its sentinel disease, the adult T-lymphoma/leukemia, but unexpicably much lower than the 50-60% of other major endemic zones of Japan and the African descendants of the Caribeean. This report describes the clinical, laboratory, and epidemiological features of leukemia and lymphoma cases diagnosed between 1982 and 1984 in the city of Ibadan, Nigeria, some of the features of which are reminiscent of the observations of Ludwig Gross’s experiments on environmental influences, such as malnutrition and infections, on animal leukemogenesis. These events are the consequences of the primordial pressures that have shaped human genetics and pathophysiology. Evidence provided in this study, indicating association of increasing socioeconomic status with increasing frequency of the c-ALL subtype, is indicative of the prospects for leukemogenesis of acute lymphoblastic leukemia and its epidemiology in Nigerians. Some findings reported here indicate the influence of the African genetic ancestry in the etiology of acute myelogenous leukemia, while socioecomic status is linked to the etiology of childhood acute lymphoblastic leukemia, as well as a variant of chronic lymphocytic leukemia, and the chloroma-associated acute myelogenous leukemia. These observations are suggestive of the existence of pathways to etiological discoveries in the leukemias. Observations reviewed in this paper reflect examples of changes that have occurred over the past 200 years in the societal perception of health challenges among the new-found communities of colonial Africa and the Americas - from the reductionistic connotations such as in the “virgin-soil theory” - towards that of social determinants of health.