REDOX IMAGING OF THE p53-DEPENDENT MITOCHONDRIAL REDOX STATE IN COLON CANCER EX VIVO

The mitochondrial redox state and its heterogeneity of colon cancer at tissue level have not been previously reported.Nor has how p53 regulates mitochondial respi ration been measured at(deep)tissue level,presumably due to the unavailability of the technology that has sufficient spatial resolution and tissue penetration depth.Our prior work demonstrated that the mito-chondrial redox state and its intnatumor heterogeneity is associated with cancer aggressiveness in human melanoma and breast cancer in mouse models,with the more metastatic tumons exhi-bit ing localized negions of more oxidized redox state.Using the Chance redox scanner with an in-plane spatial resolution of 200 pm,we imaged the mitochondrial redox state of the wild-type p53 colon tumors(HCT116 p53 ut)and the p5-deleted colon tumors(HCT116 p53-/-)by cllcting the fuorescence si gnals of nicotinamide adenine dimucleotide(NA DH)and oxidized flavoproteins [Fp,including favin adenine dinucleotide(FAD)]from the mouse xenogmafts snap frozen at low temperature.Our results show that:(1)both tumor lines have significant degree of intratumor heterogeneity of the redox state,typically exhibiting a distinct bi modal distribution that either correlates with the spatial core-rim pattern or the“hot/oold”oxida tion-roduction patches;.(2)the p531-group is significantly more beterogencous in the mitochondrial redox state and has a more oxidized turmor core compared to the p53 wt group when the tunor sizes of the two groups are matched;(3)the tumor size dependence of the redox indices(such as Fp and Fp redox ratio)is significant in the p531-group with the larger ones being more oxidized and more hetero-geneous in their redox state,particularly more oxidized in the tumor central regions;(4)the H&E staining images of tumor soctions grossly correlate with the redox images.The present work is the first to reveal at the submillimeter scale the intratumor heterogeneity pattem of the mitochon-drial redox state in colon cancer and the first to indicate that at tissue level the mitochondial redox state is p53 dependent.The findings should assist in our understanding on colon cancer pa thology and developing new imaging biomarkers for dlinical applications.

3D imaging of the mitochondrial redox state of rathearts under normal and fasting conditions

The heart requires continuous ATP availability that is generated in the mitochondria.Althoughstudies using the cell culture and perfiused organ models have been carried out to investigate thebiochemistry in the mitochondria in response to a change in substrate supply,mitochondrialbioenergetics of heart under normal feed or fasting conditions has not been studied at the tissuelevel with a sub-millimeter spatial resolution either in vivo or er vivo.Oxidation of many food-derived metabolites to generate ATP in the mitochondria is realized through the NADH/NAD+couple acting as a central electron carrier.We employed the Chance redox scanner thelow-temperat ure fluorescence scanner to image the three-dimensional(3D)spatial distribution of themitochondrial redox states in heart tissues of rats under normai feeding or an overnight star-vation for 14.5 h.Multiple consecutive sections of each heart were imaged to map three redoxindices,i.e,NADH,oxidized favoproteins Fp,including flavin adenine dinucleotide(FAD)andthe redox ratio NADH/Fp.The imaging results revealed the micro-heterogeneity and the spatial distribution of these redox indices.The quantitative analysis showed that in the fasted hearts thestandard deviation of both NADH and Fp,ie.,SD NADH and SDFp,significantly decreasedwith a p value of 0.032 and 0.045,respectively,indicating that the hearts become relatively morehomogeneous after fasting.The fasted hearts contained 28.6%less NADH(p=0.038).No sig.nificant change in Fp was foumnd(p=0.4).The NADH/Fp ratio decreased with a marginalP value(0.076).The decreased NADH im the fasted hearts is consistent with the cardiac celsreliance of fatty acids consumption for energy metabolism when glucose becomes scarce.Theexperimental o bservation of N ADH decrease induced by dietary restriction in the heart at tissuelevel has not been reported to our best knowledge.The Chance redox scanner demonstrated thefeasibility of 3D imaging of the mitochondrial redox st ate in the heart and provides a usefil toolto study heart metabolism and fiunction under normal,dietary-change and pathological con-ditions at tisue level. We would like to thank Dr.Joseph Baur for thehelpful discussion and Dr.Hui Qiao for animalpreparation and organ harvesting.