Transcriptome foundations of low FDG uptake in prostate cancer

Objectives FDG uptake in prostate cancers is commonly low for unclear reasons. We examined RNA transcriptomes of prostate cancer vs. normal prostate using microarray approaches.

Methods 69 cancer and 20 normal prostate tissues transcriptomes from prostate cancer study (GSE6956) was selected from the public GEO dataset.Affy U133A 2.0 chips were used (14,500 well characterized genes). After RMA normalization, Spotfire software analysis was performed. Each volume change of major metabolic pathways was estimated with Chi square test using Stata software.

Results Comparing gene profiles of cancer with normal tissues, 5 out of 77 probesets in glycolysis were up, & 7 probesets down in the cancer group. The balance in positive and negative direction didn't change the volume (Chi square test p=0.38). In Krebs-TCA, 5 out of 54 probesets were up and 6 down in prostate cancer. The whole volume showed no significant change (p=0.5). There was an increase of the cell cycle pathway in the prostate cancer group even though the sum change (16.9%) of up and down regulation of gene expression is smaller than that we have seen in lung cancer (64.9%). 22 of 154 probesets in prostate cancer were up and 4 of 154 probesets were down (p=0.0002). HIF, MYC, Ki67, PCNA, VDAC, and UCP were studied. There was no significant difference between cancer and normal groups.

Conclusions Prostate cancers have a mild increase in cell proliferation transcriptome , however no statistically significant changes in major glycolytic metabolic pathways in prostate cancers were seen. vs. normal prostate. These transcriptome findings help explain the relatively low FDG PET signal seen in many prostate cancers.