In a somewhat surprising series of studies, a team of researchers at Purdue University and the Indiana University School of Medicine have demonstrated that cholesterol sulfate has high potential as a marker for prostate cancer.
Eberlin et al. have been able to show that cholesterol sulfate is absent in healthy prostate tissue, but is a major fat that can be found in prostate cancer tumors and also in precancerous tissues. Their report describes the use of a new analysis technique known as desorption electrospray ionization (DESI) that allowed them to create a profile of the lipid molecules (the fats) in normal and cancerous prostate tissues. Based on this research, testing for cholesterol sulfate may offer potential for less invasive testing and improving the diagnosis of prostate cancer — but there is still a lot of work to be done.
DESI is an evolution of standard forms of mass spectrometry and was used by the Purdue research group to measure and compare the chemical characteristics of 68 samples of normal and cancerous prostate tissue. Mass spectrometry works by first turning molecules into ions, or electrically charged versions of themselves, so that they can be identified by their mass. DESI eliminates several of the complicated steps required in older forms of mass spectrometry, making it a faster process and more applicable to medical examination or surgical settings.
The team also had access to newly developed software that was able to turn the distribution and intensity of selected ions within a specific tissue sample into a computer-generated image, much like what would be seen from a stained slide under the microscope. Such chemical maps of specific tissue samples can show the location of cancerous tissue and the borders of tumors with considerable precision (as shown in the illustration below).
Figure: Images from DESI mass spectrometry analysis of prostate tissue samples are shown next to stained slides of the same samples. The images show that cholesterol sulfate is present in cancerous tissues and in high-grade prostatic intraepithelial neoplasia (HG-PIN).
Livia Eberlin, who was the lead author of the new paper in Analytical Chemistry, is quoted in a media release from Purdue University as saying that DESI showed promise in detecting precancerous lesions as well as cancerous ones.
“The DESI examination was able to distinguish a precancerous lesion in a small area of a sample made up of mostly healthy tissue,” she said. “By evaluating the difference in the chemistry of cells, this technique can detect differences in diseased tissue that are otherwise indistinguishable. It could provide a new tool for pathologists to complement microscopic examination.”
She went on to say that the research team plans to study differences in the chemistry of different types of prostate cancer tumors to see if there is a way to identify which are more aggressive aggressive and which are less so. If there is a way to tie density of cholesterol sulfate within the prostate to aggressiveness or indolence of the cancer, this would represent a potentially significant step forward in the diagnosis of prostate cancer and the treatment decision paradigm.
It is also tempting to speculate that if cholesterol sulfate levels are in some way connected to prostate cancer risk, this may offer a possible explanation for the connection between statin therapy and lowered risk for prostate cancer.