Contrasting patterns of transcript abundance in tumour tissue and cancer cell lines.

Comparison of data on transcript abundance in ovarian, prostate and colon tumours with the corresponding cancer cell lines was used to assess the similarities of expression profiles. Although transcript abundances in tumours and cell lines were positively correlated, there were substantial differences with respect to the overall expression pattern. Compared with tumours, cancer cell lines showed more variable patterns of transcript abundance among tissue types. In the ovary and colon, cancer cell lines showed greater overall transcript abundance than normal tissue; this increase was much more marked in the case of the colon. However, in the prostate, cancer cell lines showed overall reduced transcript abundance when compared with normal tissue. Principal component analyses, applied separately to each tissue type, showed that approximately 80% of the variance was explained by overall expression level differences, which were maintained across normal tissue, tumour tissue and cancer cell lines. The remaining variance ( approximately 20%) could be attributed to contrasts in expression pattern among normal tissue, tumour tissue and cancer cell lines. In each dataset and in a combined dataset of transcripts shared among the three datasets, principal components revealed both contrasts in expression pattern between tumour tissue and cancer cell lines, and common features in the expression pattern of cancer cell lines that were distinct from those of tumour tissue and were shared across the different tissue types. These results imply that data on gene expression in cancer cell lines should be used with caution in inferring gene expression of in vivo tumours.

Nonparametric spirometry reference values for Hispanic Americans.

Recent literature sites ethnic origin as a major factor in developing pulmonary function reference values. Extensive studies established reference values for European and African Americans, but not for Hispanic Americans. The Third National Health and Nutrition Examination Survey defines Hispanic as individuals of Spanish speaking cultures. While no group was excluded from the target population, sample size requirements only allowed inclusion of individuals who identified themselves as Mexican Americans. This research constructs nonparametric reference value confidence intervals for Hispanic American pulmonary function. The method is applicable to all ethnicities. We use empirical likelihood confidence intervals to establish normal ranges for reference values. Its major advantage: it is model free, but shares asymptotic properties of model based methods. Statistical comparisons indicate that empirical likelihood interval lengths are comparable to normal theory intervals. Power and efficiency studies agree with previously published theoretical results.