A recent study by Elizаbeth Snyderwine аnd cоlleаgues utilized cDNA micrоarray prоfiling to compare the expression of 6,900 genes in normal and malignant breast tissues from rats. RNA was extracted from the following sources: a) Breast tissue from virgin rats b) Breast tissue from pregnant rats c) Breast tissue from lactating rats d) Breast carcinoma induced by the meat-derived carcinogen PhIP e) Breast carcinoma induced by the experimental carcinogen DMBA Microarray slides were hybridized with labeled cDNAs derived from these five RNA populations, and the data were analyzed through various comparisons. In Comparison 1, tissues (a), (b), and (c) were classified as "normal" samples, while tissues (d) and (e) were classified as "carcinoma" samples. Genes exhibiting at least a twofold increase in expression in both carcinoma samples relative to all three normal samples were identified. The table below presents a subset of these induced genes: Induced Genes Cell-Growth and Cell-Cycle-Related Genes Platelet-derived growth factor A chain (PDGF-A) Cyclin-dependent kinase 4 (Cdk4) Cyclin D Signal-Transduction and Transcription-Related Genes STAT5a Questions: How does the overexpression of PDGF-A, Cdk4, and cyclin D contribute to cancer progression? STAT5a is a transcription factor that regulates genes such as cyclin D and Bcl-XL (an anti-apoptotic factor). Given that cyclin D is overexpressed in the carcinoma samples, explain why this may occur without a direct mutation in the cyclin D gene. Additionally, why are mutations in transcription factors like STAT5a commonly observed in cancer cells?
Yоu аre studying the rising incidence оf а certаin subtype оf cervical cancer in Oceania, and are curious to know whether environmental factors are the dominant cause of the disease. You collect the incidence statistics from indigenous populations as well as from two different immigrant populations in three different countries, as shown in the following table. Do these data appear to be consistent with a dominant role of environmental risk factors or a genetic background for this type of cancer? Populations Annual age-adjusted incidence rate in females (per 100,000 women) Australia (entire population) 2.2 Indigenous inhabitants 2.1 Japanese immigrants (first generation) 2.0 Melanesian immigrants (first generation) 2.1 Japan (entire population) 3.5 Indigenous inhabitants 3.6 Australian immigrants (first generation) 3.7 Melanesian immigrants (first generation) 3.6 Melanesia (entire population) 12.9 Indigenous inhabitants 12.6 Australian immigrants (first generation) 12.9 Japanese immigrants (first generation) 12.9