Any reassortant would likely need more genetic changes, such as ones that made the 1957 and 1968 strains better able to bind to human respiratory tract epithelial cells, the CDC team reports today in the Proceedings of the National Academy of Sciences.
Contemporary models of bladder TCC progression suggest that tumours of a higher stage and grade have accumulated more genetic changes (Simon et al, 1998).
In general, more advanced tumors exhibit more genetic changes, although many of the changes are already present in in situ carcinomas or even in ductal hyperplasia, suggesting a progressive accumulation of genomic aberrations.
Thus, differences in the allelic loss and mutation patterns have been reported previously between squamous and adenocarcinomas, suggesting that more genetic changes accumulate during tumorigenesis in squamous cell carcinomas than in adenocarcinomas (Sato et al, 1994).
The large number and variety of structural variants seen in this relatively simple model of prostate cancer also indicates that many more genetic changes are waiting to be discovered in clinical prostate cancer as it progresses to the aggressive disease.
However, multigenic inheritance, resulting from the combination of two or more genetic changes, each imparting a low to moderately increased risk of developing dystonia and acting in combination with environmental factors, may also underlie a significant proportion of the apparent heritability of late-onset dystonia.
Second, if resistance requires two or more genetic changes, the obligate sexual recombination that occurs in the Plasmodium life cycle can break apart the gene combination(s) required to encode resistance to both components of the combination therapy, thus slowing, or even preventing, the establishment and spread of resistance (Curtis and Otoo 1986; Dye and Williams 1997; Hastings 1997).
Resistance could be accompanied by a reversible change in the tumor or could involve a more permanent genetic change in the tumor cells or endothelial cells.
