Cancer: determinants and progression.

Cancer is the combination of uncontrolled cellular proliferation and immortality. It is a multi-step disease with a multi-factorial etiology. The determinants of cancer are many and varied including genetic predisposition, environmental influences, infectious agents, nutritional factors, hormonal and reproductive factors, radiation etc. However, the extent of the genetic involvement and their interaction with environment in tumorigenesis is still elusive. The six essential alterations in cell are proposed which determines the transition from normal cell to malignant. It includes--self-sufficiency in growth signals, insensitivity to growth-inhibitory (antigrowth) signals, evasion of programmed cell death (apoptosis), limitless replicative potential, sustained angiogenesis, and tissue invasion and metastasis. Nevertheless, the last two decades have seen rapid improvements in understanding the complex molecular mechanisms underlying tumorigenesis, yet the quest for unraveling the mystery is not over. Further study in this area is indispensable that could hold the promise of increasing our understanding of cancer etiology and possible preventive strategy.

Identification of human malaria parasites and detection of mixed infection in Thai patients by nested PCR.

The species-specific nested PCR previously described by Snounou and others, for detecting the four species of human malaria parasites, is evaluated in the current study testing 40 blood samples from malaria patients admitted during July-September, 2003, at the Hospital for Tropical Diseases, Faculty of Tropical Medicine, Mahidol University, Thailand. Parasite DNA of each blood sample was extracted and purified by QIAamp. DNA mini kit. Nested PCR was performed using genus-specific primers for the first PCR cycle and species-specific primer for the second cycle. Thin and thick smears were also made, stained with Giemsa, and examined by expert microscopists. Only one of 40 samples (2.5%) was identified as Plasmodium malariae infection by both microscopy and nested PCR. Twenty blood samples (50%) were identified as Plasmodium falciparum infections by both methods. However, 19 blood samples (47.5%) were reported as Plasmodium vivax infections by microscopic methods, whereas nested PCR could detect a mixed infection of Plasmodium vivax and Plasmodium falciparum in one sample taken from a young girl with 8 ameboid trophozoites of P. vivax per 200 white blood cells. These results demonstrated that the nested PCR assay surpasses microscopy and also offers a clear advantage in the detection of mixed infections, which is important not only for successful medical treatment, but also for the study of malaria epidemiology.