Breast cancer heterogeneity in histology and molecular subtype influences metabolic and proliferative activity and hence the acid load on cancer cells. We hypothesized that acid-base transporters and intracellular pH (pHi) dynamics contribute inter-individual variability in breast cancer aggressiveness and prognosis. We show that Na+,HCO3--cotransport and Na+/H+-exchange dominate cellular net acid extrusion in human breast carcinomas. Na+/H+-exchange elevates pHi preferentially in estrogen receptor-negative breast carcinomas, whereas Na+,HCO3--cotransport raises pHi more in invasive lobular than ductal breast carcinomas and in higher malignancy grade breast cancer. HER2-positive breast carcinomas have elevated protein expression of Na+/H+-exchanger NHE1/SLC9A1 and Na+,HCO3--cotransporter NBCn1/SLC4A7. Increased dependency on Na+,HCO3--cotransport associates with severe breast cancer: enlarged CO2/HCO3--dependent rises in pHi predict accelerated cell proliferation; whereas enhanced CO2/HCO3--dependent net acid extrusion, elevated NBCn1 protein expression, and reduced NHE1 protein expression predict lymph node metastasis. Accordingly, we observe reduced survival for patients suffering from Luminal A or Basal-like/triple-negative breast cancer with high SLC4A7 and/or low SLC9A1 mRNA expression. We conclude that the molecular mechanisms of acid-base regulation depend on clinicopathological characteristics of breast cancer patients. NBCn1 expression and dependency on Na+,HCO3--cotransport for pHi regulation, measured in biopsies of human primary breast carcinomas, independently predict proliferative activity, lymph node metastasis, and patient survival.
Ischemia-reperfusion injury is one of the major problems in reconstructive microsurgery. The ischemic insult may be due to an occlusion of either the artery or the vein. Clinical observations have suggested that flap survival is more sensitive to venous stasis than to arterial ischemia. The current study evaluated the viability of the myocutaneous rectus abdominis flap following secondary arterial or venous occlusion and its possible dependency on tissue metabolites and length of the preceding reperfusion period. Forty-eight bilateral 5 X 10 cm myocutaneous rectus abdominis flaps were elevated in 24 pigs and exposed to consecutive periods of primary ischemia (2 hours), reperfusion (1, 4, 8, and 12 hours), and secondary pedicle occlusion (6, 8, 10, 12, 14, or 16 hours) of arterial or venous origin. Muscle adenosine triphosphate (ATP) and glucose-6-phosphate (G6P) were assessed immediately after flap elevation, at the end of primary ischemia, after reperfusion, and at the end of secondary ischemia. Flap viability was assessed 5 days after the operation. Secondary venous occlusion resulted in reduced survival rates as compared with arterial occlusion (9 of 24 versus 20 of 24; p < 0.01), although the average ATP content was higher in flaps subjected to venous stasis [median (25 to 75) percentiles, 3.7 (1.7 to 7.1) micromol/gm protein] than in those subjected to arterial ischemia 1.2 (0.8 to 1.8 micromol/gm protein) (p < 0.01). During reperfusion, muscle ATP decreased from 28.5 (17.9 to 36.6) micromol/gm protein to 15.4 (7.4 to 24.9) micromol/gm protein (p < 0.01) and glucose-6-phosphate from 7.6 (4.1 to 11.6) micromol/gm protein to 1.0 (0.5 to 4.1) micromol/gm protein (p < 0.01). Still, flap survival following secondary arterial ischemia was improved by increasing the reperfusion time from 1 to 8 hours (p < 0.05). No effect of reperfusion time was seen on viability after venous stasis. In conclusion, despite poorer flap survival, venous stasis was less detrimental to tissue ATP level, suggesting that the continued inflow may have supplied substrates for glycolysis. Furthermore, the larger blood volume may have accumulated the glycolytic waste products. After reperfusion, the recovery of aerobic metabolism was far from complete, and cellular glycolytic substrates were nearly exhausted. However, prolongation of the reperfusion time preceding secondary arterial ischemia improved flap survival.
Background Carbonic anhydrases catalyze CO2/HCO3– buffer reactions with implications for effective H+ mobility, pH dynamics, and cellular acid–base sensing. Yet, the integrated consequences of carbonic anhydrases for cancer and stromal cell functions, their interactions, and patient prognosis are not yet clear. Methods We combine (a) bioinformatic analyses of human proteomic data and bulk and single-cell transcriptomic data coupled to clinicopathologic and prognostic information; (b) ex vivo experimental studies of gene expression in breast tissue based on quantitative reverse transcription and polymerase chain reactions, intracellular and extracellular pH recordings based on fluorescence confocal microscopy, and immunohistochemical protein identification in human and murine breast cancer biopsies; and (c) in vivo tumor size measurements, pH-sensitive microelectrode recordings, and microdialysis-based metabolite analyses in mice with experimentally induced breast carcinomas. Results Carbonic anhydrases—particularly the extracellular isoforms CA4, CA6, CA9, CA12, and CA14—undergo potent expression changes during human and murine breast carcinogenesis. In patients with basal-like/triple-negative breast cancer, elevated expression of the extracellular carbonic anhydrases negatively predicts survival, whereas, surprisingly, the extracellular carbonic anhydrases positively predict patient survival in HER2/ErbB2-enriched breast cancer. Carbonic anhydrase inhibition attenuates cellular net acid extrusion and extracellular H+ elimination from diffusion-restricted to peripheral and well-perfused regions of human and murine breast cancer tissue. Supplied in vivo, the carbonic anhydrase inhibitor acetazolamide acidifies the microenvironment of ErbB2-induced murine breast carcinomas, limits tumor immune infiltration (CD3+ T cells, CD19+ B cells, F4/80+ macrophages), lowers inflammatory cytokine (Il1a, Il1b, Il6) and transcription factor (Nfkb1) expression, and accelerates tumor growth. Supporting the immunomodulatory influences of carbonic anhydrases, patient survival benefits associated with high extracellular carbonic anhydrase expression in HER2-enriched breast carcinomas depend on the tumor inflammatory profile. Acetazolamide lowers lactate levels in breast tissue and blood without influencing breast tumor perfusion, suggesting that carbonic anhydrase inhibition lowers fermentative glycolysis. Conclusions We conclude that carbonic anhydrases (a) elevate pH in breast carcinomas by accelerating net H+ elimination from cancer cells and across the interstitial space and (b) raise immune infiltration and inflammation in ErbB2/HER2-driven breast carcinomas, restricting tumor growth and improving patient survival.
Intracellular Ca2+ dynamics shape malignant behaviors of cancer cells. Whereas previous studies focused on cultured cancer cells, we here used breast organoids and colonic crypts freshly isolated from human and murine surgical biopsies. We performed fluorescence microscopy to evaluate intracellular Ca2+ concentrations in breast and colon cancer tissue with preferential focus on intracellular Ca2+ release in response to purinergic and cholinergic stimuli. Inhibition of the sarco‐/endoplasmic reticulum Ca2+ ATPase with cyclopiazonic acid elicited larger Ca2+ responses in breast cancer tissue, but not in colon cancer tissue, relative to respective normal tissue. The resting intracellular Ca2+ concentration was elevated, and ATP, UTP and acetylcholine induced strongly augmented intracellular Ca2+ responses in breast cancer tissue compared with normal breast tissue. In contrast, resting intracellular Ca2+ levels and acetylcholine‐induced increases in intracellular Ca2+ concentrations were unaffected and ATP‐ and UTP‐induced Ca2+ responses were smaller in colon cancer tissue compared with normal colon tissue. In accordance with the amplified Ca2+ responses, ATP and UTP substantially increased proliferative activity—evaluated by bromodeoxyuridine incorporation—in breast cancer tissue, whereas the effect was minimal in normal breast tissue. ATP caused cell death—identified with ethidium homodimer‐1 staining—in breast cancer tissue only at concentrations above the expected pathophysiological range. We conclude that intracellular Ca2+ responses are amplified in breast cancer tissue, but not in colon cancer tissue, and that nucleotide signaling stimulates breast cancer cell proliferation within the extracellular concentration range typical for solid cancer tissue.
A new determination of the value of Eve's constant, which employed three ionization‐chambers of various sizes having area‐volume ratios of 0.249, 0.848, and 0.504, respectively, is described. Applying necessary corrections and extrapolating to zero area‐volume ratio, a value of Eve's constant of 4.63×109 ion‐pairs per cc per gm radium in air at NTP is deduced.
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