Multiphase mechanics of capsule formation in tumors

The presence of a capsule around a tumor is known to be correlated with benign status, and the absence of a capsule often has negative implications for patient prognosis. A mechanical description is presented of the growth of a tumor and the resulting deformations of surrounding normal tissue. A mathematical model of the mechanics is analyzed using physical parameters measured in vivo and in vitro. The model has only three dimensionless parameters, and its results are very robust with respect to parameter variation. We show that the presence of contractility in the surrounding tissue, corresponding to a host defense, can make an existing capsule denser and constrain the tumor better, but cannot be responsible for the observed pressure gradients in encapsulated tumors. Some implications for treatment are discussed.

The IDDM13 region containing the insulin-like growth factor binding protein-5 (IGFBP5) gene on chromosome 2q33-q36 and the genetic susceptibility to rheumatoid arthritis

We considered that the constitutive over-expression by cultured rheumatoid arthritis (RA) fibroblast-lineage synoviocytes of genes like IGFBP5 could indicate new candidate susceptibility genes. IGFBP5 is located in a region where an insulin-dependent diabetes mellitus (IDDM) susceptibility locus, IDDM13 (2q33-q36), has been mapped. Previous evidence that non-MHC IDDM loci overlap RA susceptibility loci made IGFBP5 and its region an interesting candidate locus which was tested for linkage. Forty-nine sibships (2-4 affected siblings per sibship) with RA were genotyped with microsatellite markers covering an 11.2 cM interval in the IGFBP5/IDDM13 region. Both the two-point LOD scores and a 'nonparametric' allele-sharing analysis revealed no evidence for linkage (max LOD = 0.54, P = 0.5, respectively). Adjustments for the presence of 'shared-epitope' alleles did not significantly change the LOD scores. These results suggest that, despite the involvement of the 2q33-q36 chromosomal region in another organ-specific autoimmune disease, it is unlikely that this region harbors a RA susceptibility locus.