Label-free optical biomarker for prostate cancer diagnosis

Abstract

Reprogramming of cellular metabolism in cancer leads to changes in the activity of metabolic coenzymes NAD(P)H and FAD which can be used as markers of tumorigenesis and metastasis. NAD(P)H and FAD form coupled redox pair and regulator of mitochondrial energy metabolism. Since NAD(P)H and FAD are endogenous and auto fluorescent, the coupled redox pair can hence be exploited as a reporter for metabolic activity in tumor microenvironment. We have developed a 2P-FLIRR assay (2-photon Fluorescence Lifetime based Redox Ratio), a sensitive metabolic optical biomarker for tumor diagnosis in prostate cancer (PCa) patients’ tissue sections. We have imaged and used our novel 2P-FLIRR metric which is the ratio of the enzyme-bound fractions of NAD(P)H and FAD to evaluate PCa patients’ surgically resected tissue sections. These were PCa adenocarcinomas with different Gleason grades. In comparison with conventional H&E histopathology, our 2P-FLIRR assay showed the potential to distinguish tumor-enriched regions from normal prostate tissue in unstained frozen patient tissue sections. Lower FLIRR values were observed to correspond to tumor versus higher FLIRR values to normal prostate. This pilot feasibility study demonstrates that 2P-FLIRR detects metabolic contrast between prostate cancer and normal prostate tissue in frozen human patient tissue sections. Our study identifies for the first time quantitative 2P-FLIRR as a potential sensitive diagnostic optical biomarker for PCa.