Role of heterozygous APC mutation in niche succession and initiation of colorectal cancer--a computational study.

Mutations in the adenomatous polyposis coli (APC) gene are found in most colorectal cancers. They cause constitutive activation of proliferative pathways when both alleles of the gene are mutated. However studies on individuals with familial adenomatous polyposis (FAP) have shown that a single mutated APC allele can also create changes in the precancerous colon crypt, like increased number of stem cells, increased crypt fission, greater variability of DNA methylation patterns, and higher somatic mutation rates. In this paper, using a computational model of colon crypt dynamics, we evolve and investigate a hypothesis on the effect of heterozygous APC mutation that explains these different observations. Based on previous reports and the results from the computational model we propose the hypothesis that heterozygous APC mutation has the effect of increasing the chances for a stem cell to divide symmetrically, producing two stem cell daughters. We incorporate this hypothesis into the model and perform simulation experiments to investigate the consequences of the hypothesis. Simulations show that this hypothesis links together the changes in FAP crypts observed in previous studies. The simulations also show that an APC(+/-) stem cell gets selective advantages for dominating the crypt and progressing to cancer. This explains why most colon cancers are initiated by APC mutation. The results could have implications for preventing or retarding the onset of colon cancer in people with inherited or acquired mutation of one APC allele. Experimental validation of the hypothesis as well as investigation into the molecular mechanisms of this effect may therefore be worth undertaking.

Clinicoepidemiological profile and predictors of severe illness in young infants (< 60 days) reporting to a hospital in North India.

OBJECTIVES: To describe the clinical and epidemiological profile of young infants reporting to a hospital and assess previously proposed simple clinical signs for their value in enabling health workers to detect young infants with severe illness warranting hospital admission. METHODS: Observational study of infants less than 2 months of age presenting consecutively to a large public hospital in South Delhi who were evaluated by a health worker (nurse), on a standardized list of signs and symptoms, and the ability of these were evaluated against the need for hospital admission which was assessed by an independent pediatrician. RESULTS: Of the 1624 young infants triaged, 878 were enrolled into the study. Of these 100 (11%) were below 7 days of age, for whom the common reasons for seeking care were jaundice (52%), not feeding well (6%) and fever (5%). The remaining 778 (89%) were 7-59 days of age with respiratory symptoms as the main presenting complaints (29.1%). The primary clinical diagnoses in infants with serious illness needing admission to hospital in the age group <7 days (n = 66) were hyperbilirubinemia (56%) and sepsis (21%). In those between 7-27 days of age (n = 60), primary diagnoses were sepsis (27%), pneumonia (13%), diarrhea, dysentery or dehydration (10%), while in the age group 28-59 days of age (n = 47) pneumonia (40%), sepsis (19%) and diarrhea or dehydration (13%) were the common primary diagnoses. Signs that had at least a prevalence of 5% and were strong predictors for all the age categories studied were history of difficult feeding (OR 6.8 for 0-6 days, 15.1 for 2-27 days and 6.2 for 28-59 days age groups), not feeding well on observation (OR 13.7, 27.6 and 20.9 respectively for the 3 age groups), temperature > 37.5C (OR 21.8, 14.6 and 30.0 respectively for the 3 age groups) and respiratory rate > 60 per minute (OR 6.8, 15.1 and 21.0 respectively for the 3 age groups). Additional strong predictors with > 5% prevalence were history of convulsions (OR 7.9, only in 0-6 day age group), lethargy (OR 26.1, only in 7-27 day age group), and history of diarrhea (OR 3.0 for 2-27 days and 2.2 for 28-59 days age groups). CONCLUSIONS: Simple clinical signs are useful in hands of health worker for identifying neonates with serious illness warranting hospital admission. These will be of use in the further development of clinical algorithms for the national integrated management of childhood illnesses.