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Mitochondrial oxidative stress in cancer-associated fibroblasts drives lactate production, promoting breast cancer tumor growth: understanding the aging and cancer connection.Increasing chronological age is the most significant risk factor for cancer. Recently, we proposed a new paradigm for understanding the role of the aging and the tumor microenvironment in cancer onset. In this model, cancer cells induce oxidative stress in adjacent stromal fibroblasts. This, in turn, causes several changes in the phenotype of the fibroblast including mitochondrial dysfunction, hydrogen peroxide production, and aerobic glycolysis, resulting in high levels of L-lactate production. L-lactate is then transferred from these glycolytic fibroblasts to adjacent epithelial cancer cells and used as "fuel" for oxidative mitochondrial metabolism. Here, we created a new pre-clinical model system to directly test this hypothesis experimentally. To synthetically generate glycolytic fibroblasts, we genetically-induced mitochondrial dysfunction by knocking down TFAM using an sh-RNA approach. TFAM is mitochondrial transcription factor A, which is important in functionally maintaining the mitochondrial respiratory chain. Interestingly, TFAM-deficient fibroblasts showed evidence of mitochondrial dysfunction and oxidative stress, with the loss of certain mitochondrial respiratory chain components, and the over-production of hydrogen peroxide and L-lactate. Thus, TFAM-deficient fibroblasts underwent metabolic reprogramming towards aerobic glycolysis. Most importantly, TFAM-deficient fibroblasts significantly promoted tumor growth, as assayed using a human breast cancer (MDA-MB-231) xenograft model. These increases in glycolytic fibroblast driven tumor growth were independent of tumor angiogenesis. Mechanistically, TFAM-deficient fibroblasts increased the mitochondrial activity of adjacent epithelial cancer cells in a co-culture system, as seen using MitoTracker. Finally, TFAM-deficient fibroblasts also showed a loss of caveolin-1 (Cav-1), a known breast cancer stromal biomarker. Loss of stromal fibroblast Cav-1 is associated with early tumor recurrence, metastasis, and treatment failure, resulting in poor clinical outcome in breast cancer patients. Thus, this new experimental model system, employing glycolytic fibroblasts, may be highly clinically relevant. These studies also have implications for understanding the role of hydrogen peroxide production in oxidative damage and "host cell aging," in providing a permissive metabolic microenvironment for promoting and sustaining tumor growth.
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Equivalence of three or four cycles of bleomycin, etoposide, and cisplatin chemotherapy and of a 3- or 5-day schedule in good-prognosis germ cell cancer: a randomized study of the European Organization for Research and Treatment of Cancer Genitourinary Tract Cancer Cooperative Group and the Medical Research Council.PURPOSE: To test the equivalence of three versus four cycles of bleomycin, etoposide, and cisplatin (BEP) and of the 5-day schedule versus 3 days per cycle in good-prognosis germ cell cancer. PATIENTS AND METHODS: The study was designed as a 2 x 2 factorial trial. The aim was to rule out a 5% decrease in the 2-year progression-free survival (PFS) rate. The study included the assessment of patient quality of life. A cycle of BEP consisted of etoposide 500 mg/m(2), administered at either 100 mg/m(2) days 1 through 5 or 165 mg/m(2) days 1 through 3, cisplatin 100 mg/m(2), administered at either 20 mg/m(2) days 1 through 5 or 50 mg/m(2) days 1 and 2. Bleomycin 30 mg was administered on days 1, 8, and 15 during cycles 1 through 3. The randomization procedure allowed some investigators to participate only in the comparison of three versus four cycles. RESULTS: From March 1995 until April 1998, 812 patients were randomly assigned to receive three or four cycles: of these, 681 were also randomly assigned to the 5-day or the 3-day schedule. Histology, marker values, and disease extent are well balanced in the treatment arms of the two comparisons. The projected 2-year PFS is 90.4% on three cycles and 89.4% on four cycles. The difference in PFS between three and four cycles is -1.0% (80% confidence limit [CL], -3.8%, +1.8%). Equivalence for three versus four cycles is claimed because both the upper and lower bounds of the 80% CL are less than 5%. In the 5- versus 3-day comparison, the projected 2-year PFS is 88.8% and 89.7%, respectively (difference, -0.9%, (80% CL, -4.1%, +2.2%). Hence, equivalence is claimed in this comparison also. Frequencies of hematologic and nonhematologic toxicities were essentially similar. Quality of life was maintained better in patients receiving three cycles; no differences were detected between 3 and 5 days of treatment. CONCLUSION: We conclude that three cycles of BEP, with etoposide at 500 mg/m(2), is sufficient therapy in good-prognosis germ cell cancer and that the administration of the chemotherapy in 3 days has no detrimental effect on the effectiveness of the BEP regimen.
