Glucose uptake and intracellular pH in a mouse model of ductal carcinoma In Situ (DCIS) suggests metabolic heterogeneity

TY - JOUR

T1 - Glucose uptake and intracellular pH in a mouse model of ductal carcinoma In Situ (DCIS) suggests metabolic heterogeneity

AU - Lobo, Rebecca C.

AU - Hubbard, Neil

AU - Damonte, Patrizia

AU - Mori, Hidetoshi

AU - Pénzváltó, Zsófia

AU - Pham, Cindy

AU - Koehne, Amanda L.

AU - Go, Aiza C.

AU - Anderson, Steve E.

AU - Cala, Peter M

AU - Borowsky, Alexander D

PY - 2016/8/31

Y1 - 2016/8/31

N2 - Mechanisms for the progression of ductal carcinoma in situ (DCIS) to invasive breast carcinoma remain unclear. Previously we showed that the transition to invasiveness in the mammary intraepithelial neoplastic outgrowth (MINO) model of DCIS does not correlate with its serial acquisition of genetic mutations. We hypothesized instead that progression to invasiveness depends on a change in the microenvironment and that precancer cells might create a more tumor-permissive microenvironment secondary to changes in glucose uptake and metabolism. Immunostaining for glucose transporter 1 (GLUT1) and the hypoxia marker carbonic anhydrase 9 (CAIX) in tumor, normal mammary gland and MINO (precancer) tissue showed differences in expression. The uptake of the fluorescent glucose analog dye, 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-D-glucose (2-NBDG), reflected differences in the cellular distributions of glucose uptake in normal mammary epithelial cells (nMEC), MINO, and Met1 cancer cells, with a broad distribution in the MINO population. The intracellular pH (pHi) measured using the fluorescent ratio dye 2',7'-bis(2-carboxyethyl)-5(6)-155 carboxyfluorescein (BCECF) revealed expected differences between normal and cancer cells (low and high, respectively), and a mixed distribution in the MINO cells, with a subset of cells in the MINO having an increased rate of acidification when proton efflux was inhibited. Invasive tumor cells had a more alkaline baseline pH i with high rates of proton production coupled with higher rates of proton export, compared with nMEC. MINO cells displayed considerable variation in baseline pH i that separated into two distinct populations: MINO high and MINO low. MINO high had a noticeably higher mean acidification rate compared with nMEC, but relatively high baseline pH i similar to tumor cells. MINO low cells also had an increased acidification rate compared with nMEC, but with a more acidic pH i similar to nMEC. These findings demonstrate that MINO is heterogeneous with respect to intracellular pH regulation which may be associated with an acidified regional microenvironment. A change in the pH of the microenvironment might contribute to a tumor-permissive or tumor-promoting progression. We are not aware of any previous work showing that a sub-population of cells in in situ precancer exhibits a higher than normal proton production and export rate.

AB - Mechanisms for the progression of ductal carcinoma in situ (DCIS) to invasive breast carcinoma remain unclear. Previously we showed that the transition to invasiveness in the mammary intraepithelial neoplastic outgrowth (MINO) model of DCIS does not correlate with its serial acquisition of genetic mutations. We hypothesized instead that progression to invasiveness depends on a change in the microenvironment and that precancer cells might create a more tumor-permissive microenvironment secondary to changes in glucose uptake and metabolism. Immunostaining for glucose transporter 1 (GLUT1) and the hypoxia marker carbonic anhydrase 9 (CAIX) in tumor, normal mammary gland and MINO (precancer) tissue showed differences in expression. The uptake of the fluorescent glucose analog dye, 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-D-glucose (2-NBDG), reflected differences in the cellular distributions of glucose uptake in normal mammary epithelial cells (nMEC), MINO, and Met1 cancer cells, with a broad distribution in the MINO population. The intracellular pH (pHi) measured using the fluorescent ratio dye 2',7'-bis(2-carboxyethyl)-5(6)-155 carboxyfluorescein (BCECF) revealed expected differences between normal and cancer cells (low and high, respectively), and a mixed distribution in the MINO cells, with a subset of cells in the MINO having an increased rate of acidification when proton efflux was inhibited. Invasive tumor cells had a more alkaline baseline pH i with high rates of proton production coupled with higher rates of proton export, compared with nMEC. MINO cells displayed considerable variation in baseline pH i that separated into two distinct populations: MINO high and MINO low. MINO high had a noticeably higher mean acidification rate compared with nMEC, but relatively high baseline pH i similar to tumor cells. MINO low cells also had an increased acidification rate compared with nMEC, but with a more acidic pH i similar to nMEC. These findings demonstrate that MINO is heterogeneous with respect to intracellular pH regulation which may be associated with an acidified regional microenvironment. A change in the pH of the microenvironment might contribute to a tumor-permissive or tumor-promoting progression. We are not aware of any previous work showing that a sub-population of cells in in situ precancer exhibits a higher than normal proton production and export rate.

KW - Ductal carcinoma in situ

KW - Glucose uptake

KW - Intracellular pH

KW - Mouse mammary carcinoma model

KW - Proton export

KW - Tumor heterogeneity

KW - Tumor microenvironment

UR - http://www.scopus.com/inward/record.url?scp=85019319075&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85019319075&partnerID=8YFLogxK

U2 - 10.3389/fcell.2016.00093

DO - 10.3389/fcell.2016.00093

M3 - Article

AN - SCOPUS:85019319075

VL - 4

JO - Frontiers in Cell and Developmental Biology

JF - Frontiers in Cell and Developmental Biology

SN - 2296-634X

IS - AUG

M1 - 93

ER -