Meeting report: genetic environmental interactions in cancer susceptibility in animal models

The not-so-sweet side of sugar: Influence of the microenvironment on the processes that unleash cancer

The role of "aerobic glycolysis" in cancer has been examined often in the past. Results from those studies, most of which were performed on two dimensional conditions (2D, tissue culture plastic), demonstrate that aerobic glycolysis occurs as a consequence of oncogenic events. These oncogenic events often drive malignant cell growth and survival. Although 2D based experiments are useful in elucidating the molecular mechanisms of oncogenesis, they fail to take contributions of the extracellular microenvironment into account. Indeed we, and others, have shown that the cellular microenvironment is essential in regulating processes that induce and/or suppress the malignant phenotype/properties. This regulation between the cell and its microenvironment is both dynamic and reciprocal and involves the integration of cellular signaling networks in the right context. Therefore, given our previous demonstration of the effect of the microenvironment including tissue architecture and media composition on gene expression and the integration of signaling events observed in three-dimension (3D), we hypothesized that glucose uptake and metabolism must also be essential components of the tissue's signal "integration plan" - that is, if uptake and metabolism of glucose were hyperactivated, the canonical oncogenic pathways should also be similarly activated. This hypothesis, if proven true, suggests that direct inhibition of glucose metabolism in cancer cells should either suppress or revert the malignant phenotype in 3D. Here, we review the up-to-date progress that has been made towards understanding the role that glucose metabolism plays in oncogenesis and re-establishing basally polarized acini in malignant human breast cells.

Case-parents design for gene-environment interaction

The scientific and public health implications of gene-environment interaction warrant that the most powerful study designs and methods of analysis be used. Because traditional case-control designs, which use nonrelated subjects, have demonstrated the need for large samples to detect interactions, alternative study designs may be worthwhile, such as sampling diseased cases and their parents. If the transmission of particular alleles from parents to their diseased child appears to be distorted from Mendelian expectation, then this suggests an etiologic association of the alleles with disease; if the frequency of transmission differs between exposed and nonexposed cases, then gene-environment interaction is suggested. We present likelihood-based methods to assess interaction, as well as an extension of the transmission/disequilibrium test (TDT). For these statistical tests, we also derive methods to compute sample size and power. Comparisons of sample size requirements between the case-parents design and the case-control design indicate that the case-parents design can be more powerful to detect gene-environment interactions, particularly when the disease susceptible allele is rare. Also, one of the derived likelihood methods, based on additive effects of alleles, tended to be the most robust in terms of power for a broad range of genetic mechanisms, and so may be useful for broad applications to assess gene-environment interactions.