Voluntary exercise does not always suppress lung cancer progression.

Physical exercise can lower lung cancer incidence. However, its effect on lung cancer progression is less understood. Studies on exercising mice have shown decreased ectopic lung cancer growth through the secretion of interleukin-6 from muscles and the recruitment of natural killer (NK) cells to tumors. We asked if exercise suppresses lung cancer in an orthotopic model also. Single-housed C57Bl/6 male mice in cages with running wheels were tail vein-injected with LLC1.1 lung cancer cells, and lung tumor nodules were analyzed. Exercise did not affect lung cancer. Therefore, we also tested the effect of exercise on a subcutaneous LLC1 tumor and a tail vein-injected B16F10 melanoma model. Except for one case of excessive exercise, tumor progression was not influenced. Moderately exercising mice did not increase IL-6 or recruit NK cells to the tumor. Our data suggest that the exercise dose may dictate how efficiently the immune system is stimulated and controls tumor progression.

Endogenous myoglobin expression in mouse models of mammary carcinoma reduces hypoxia and metastasis in PyMT mice.

Myoglobin (MB) is expressed in different cancer types and may act as a tumor suppressor in breast cancer. The mechanisms by which basal MB expression level impacts murine mammary tumorigenesis are unclear. We investigated how MB expression in breast cancer influences proliferation, metastasis, tumor hypoxia, and chemotherapy treatment in vivo. We crossed PyMT and WapCreTrp53flox mammary cancer mouse models that differed in tumor grade/type and onset of mammary carcinoma with MB knockout mice. The loss of MB in WapCre;Trp53flox mice did not affect tumor development and progression. On the other hand, loss of MB decreased tumor growth and increased tissue hypoxia as well as the number of lung metastases in PyMT mice. Furthermore, Doxorubicin therapy prevented the stronger metastatic propensity of MB-deficient tumors in PyMT mice. This suggests that, although MB expression predicts improved prognosis in breast cancer patients, MB-deficient tumors may still respond well to first-line therapies. We propose that determining the expression level of MB in malignant breast cancer biopsies will improve tumor stratification, outcome prediction, and personalized therapy in cancer patients.

Myoglobin regulates fatty acid trafficking and lipid metabolism in mammary epithelial cells.

Myoglobin (MB) is known to bind and deliver oxygen in striated muscles at high expression levels. MB is also expressed at much reduced levels in mammary epithelial cells, where the protein´s function is unclear. In this study, we aim to determine whether MB impacts fatty acid trafficking and facilitates aerobic fatty acid ß-oxidation in mammary epithelial cells. We utilized MB-wildtype versus MB-knockout mice and human breast cancer cells to examine the impact of MB and its oxygenation status on fatty acid metabolism in mouse milk and mammary epithelia. MB deficient cells were generated through CRISPR/Cas9 and TALEN approaches and exposed to various oxygen tensions. Fatty acid profiling of milk and cell extracts were performed along with cell labelling and immunocytochemistry. Our findings show that MB expression in mammary epithelial cells promoted fatty acid oxidation while reducing stearyl-CoA desaturase activity for lipogenesis. In cells and milk product, presence of oxygenated MB significantly elevated indices of limited fatty acid ß-oxidation, i.e., the organelle-bound removal of a C2 moiety from long-chain saturated or monounsaturated fatty acids, thus shifting the composition toward more saturated and shorter fatty acid species. Presence of the globin also increased cytoplasmic fatty acid solubility under normoxia and fatty acid deposition to lipid droplets under severe hypoxia. We conclude that MB can function in mammary epithelia as intracellular O2-dependent shuttle of oxidizable fatty acid substrates. MB's impact on limited oxidation of fatty acids could generate inflammatory mediator lipokines, such as 7-hexadecenoate. Thus, the novel functions of MB in breast epithelia described herein range from controlling fatty acid turnover and homeostasis to influencing inflammatory signalling cascade. Future work is needed to analyse to what extent these novel roles of MB also apply to myocytic cell physiology and malignant cell behaviour, respectively.

Pro-Apoptotic and Anti-Invasive Properties Underscore the Tumor-Suppressing Impact of Myoglobin on a Subset of Human Breast Cancer Cells.

The expression of myoglobin (MB), well known as the oxygen storage and transport protein of myocytes, is a novel hallmark of the luminal subtype in breast cancer patients and correlates with better prognosis. The mechanisms by which MB impacts mammary tumorigenesis are hitherto unclear. We aimed to unravel this role by using CRISPR/Cas9 technology to generate MB-deficient clones of MCF7 and SKBR3 breast cancer cell lines and subsequently characterize them by transcriptomics plus molecular and functional analyses. As main findings, loss of MB at normoxia upregulated the expression of cell cyclins and increased cell survival, while it prevented apoptosis in MCF7 cells. Additionally, MB-deficient cells were less sensitive to doxorubicin but not ionizing radiation. Under hypoxia, the loss of MB enhanced the partial epithelial to mesenchymal transition, thus, augmenting the migratory and invasive behavior of cells. Notably, in human invasive mammary ductal carcinoma tissues, MB and apoptotic marker levels were positively correlated. In addition, MB protein expression in invasive ductal carcinomas was associated with a positive prognostic value, independent of the known tumor suppressor p53. In conclusion, we provide multiple lines of evidence that endogenous MB in cancer cells by itself exerts novel tumor-suppressive roles through which it can reduce cancer malignancy.

Erythropoietin receptor regulates tumor mitochondrial biogenesis through iNOS and pAKT.

Erythropoietin receptor (EPOR) is widely expressed in healthy and malignant tissues. In certain malignancies, EPOR stimulates tumor growth. In healthy tissues, EPOR controls processes other than erythropoiesis, including mitochondrial metabolism. We hypothesized that EPOR also controls the mitochondrial metabolism in cancer cells. To test this hypothesis, we generated EPOR-knockdown cancer cells to grow tumor xenografts in mice and analyzed tumor cellular respiration via high-resolution respirometry. Furthermore, we analyzed cellular respiratory control, mitochondrial content, and regulators of mitochondrial biogenesis in vivo and in vitro in different cancer cell lines. Our results show that EPOR controls tumor growth and mitochondrial biogenesis in tumors by controlling the levels of both, pAKT and inducible NO synthase (iNOS). Furthermore, we observed that the expression of EPOR is associated with the expression of the mitochondrial marker VDAC1 in tissue arrays of lung cancer patients, suggesting that EPOR indeed helps to regulate mitochondrial biogenesis in tumors of cancer patients. Thus, our data imply that EPOR not only stimulates tumor growth but also regulates tumor metabolism and is a target for direct intervention against progression.

Iron- and erythropoietin-resistant anemia in a spontaneous breast cancer mouse model.

Anemia of cancer (AoC) with its multifactorial etiology and complex pathology is a poor prognostic indicator for cancer patients. One of the main causes of AoC is cancer-associated inflammation that activates mechanisms, commonly observed in anemia of inflammation, whereby functional iron deficiency and iron-restricted erythropoiesis are induced by increased hepcidin levels in response to raised levels of interleukin-6. So far only a few AoC mouse models have been described, and most of them did not fully recapitulate the interplay of anemia, increased hepcidin levels and functional iron deficiency in human patients. To test if the selection and the complexity of AoC mouse models dictates the pathology or if AoC in mice per se develops independently of iron deficiency, we characterized AoC in Trp53floxWapCre mice that spontaneously develop breast cancer. These mice developed AoC associated with high levels of interleukin-6 and iron deficiency. However, hepcidin levels were not increased and hypoferremia coincided with anemia rather than causing it. Instead, an early shift in the commitment of common myeloid progenitors from the erythroid to the myeloid lineage resulted in increased myelopoiesis and in the excessive production of neutrophils that accumulate in necrotic tumor regions. This process could not be prevented by either iron or erythropoietin treatment. Trp53floxWapCre mice are the first mouse model in which erythropoietin-resistant anemia is described and may serve as a disease model to test therapeutic approaches for a subpopulation of human cancer patients with normal or corrected iron levels who do not respond to erythropoietin.

Myoglobin, expressed in brown adipose tissue of mice, regulates the content and activity of mitochondria and lipid droplets.

The identification of novel physiological regulators that stimulate energy expenditure through brown adipose tissue (BAT) activity in substrate catalysis is of utmost importance to understand and treat metabolic diseases. Myoglobin (MB), known to store or transport oxygen in heart and skeletal muscles, has recently been found to bind fatty acids with physiological constants in its oxygenated form (i.e., MBO2). Here, we investigated the in vivo effect of MB expression on BAT activity. In particular, we studied mitochondrial function and lipid metabolism as essential determinants of energy expenditure in this tissue. We show in a MB-null (MBko) mouse model that MB expression in BAT impacts on the activity of brown adipocytes in a twofold manner: i) by elevating mitochondrial density plus maximal respiration capacity, and through that, by stimulating BAT oxidative metabolism along with the organelles` uncoupled respiration; and ii) by influencing the free fatty acids pool towards a palmitate-enriched composition and shifting the lipid droplet (LD) equilibrium towards higher counts of smaller droplets. These metabolic changes were accompanied by the up-regulated expression of thermogenesis markers UCP1, CIDEA, CIDEC, PGC1-α and PPAR-α in the BAT of MB wildtype (MBwt) mice. Along with the emergence of the "browning" BAT morphology, MBwt mice exhibited a leaner phenotype when compared to MBko littermates at 20 weeks of age. Our data shed novel insights into MB's role in linking oxygen and lipid-based thermogenic metabolism. The findings suggest potential new strategies of targeting the MB pathway to treat metabolic disorders related to diminishing energy expenditure.

P450Jα : A New, Robust and α-Selective Fatty Acid Hydroxylase Displaying Unexpected 1-Alkene Formation.

Oxyfunctionalization of fatty acids (FAs) is a key step in the design of novel synthetic pathways for biobased/biodegradable polymers, surfactants and fuels. Here, we show the isolation and characterization of a robust FA α-hydroxylase (P450Jα ) which catalyses the selective conversion of a broad range of FAs (C6:0-C16:0) and oleic acid (C18:1) with H2 O2 as oxidant. Under optimized reaction conditions P450Jα yields α-hydroxy acids all with >95 % regioselectivity, high specific activity (up to 15.2 U mg-1 ) and efficient coupling of oxidant to product (up to 85 %). Lauric acid (C12:0) turned out to be an excellent substrate with respect to productivity (TON=394 min-1 ). On preparative scale, conversion of C12:0 reached 83 % (0.9 g L-1 ) when supplementing H2 O2 in fed-batch mode. Under similar conditions P450Jα allowed further the first biocatalytic α-hydroxylation of oleic acid (88 % conversion on 100 mL scale) at high selectivity and in good yields (1.1 g L-1 ; 79 % isolated yield). Unexpectedly, P450Jα displayed also 1-alkene formation from shorter chain FAs (≤C10:0) showing that oxidative decarboxylation is more widely distributed across this enzyme family than reported previously.

Functional crosstalk between AKT/mTOR and Ras/MAPK pathways in hepatocarcinogenesis: implications for the treatment of human liver cancer.

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide, with limited treatment options. AKT/mTOR and Ras/MAPK pathways are frequently deregulated in human hepatocarcinogenesis. Recently, we generated an animal model characterized by the co-expression of activated forms of AKT and Ras in the mouse liver. We found that concomitant activation of AKT/mTOR and Ras/MAPK cascades leads to rapid liver tumor development in AKT/Ras mice, mainly through mTORC1 induction. To further define the role of mTORC1 cascade in AKT/Ras induced HCC development, the mTORC1 inhibitor Rapamycin was administered to AKT/Ras mice at the time when small tumors started to emerge in the liver. Of note, Rapamycin treatment significantly delayed hepatocarcinogenesis in AKT/Ras mice. However, some microscopic lesions persisted in the livers of AKT/Ras mice despite the treatment and rapidly gave rise to HCC following Rapamycin withdrawal. Mechanistically, Rapamycin inhibited mTORC1 and mTORC2 pathways, lipogenesis and glycolysis, resulting in inhibition of proliferation in the treated livers. However, activated ERK and its downstream effectors, Mnk1 and eIF4E, were strongly upregulated in the residual lesions. Concomitant suppression of AKT/mTOR and Ras/MAPK pathways was highly detrimental for the growth of AKT/Ras cells in vitro. The study indicates the existence of a complex interplay between AKT/mTOR and Ras/MAPK pathways during hepatocarcinogenesis, with important implications for the understanding of HCC pathogenesis as well as for its prevention and treatment.

AKT (v-akt murine thymoma viral oncogene homolog 1) and N-Ras (neuroblastoma ras viral oncogene homolog) coactivation in the mouse liver promotes rapid carcinogenesis by way of mTOR (mammalian target of rapamycin complex 1), FOXM1 (forkhead box M1)/SKP2, and c-Myc pathways.

UNLABELLED: Activation of v-akt murine thymoma viral oncogene homolog (AKT) and Ras pathways is often implicated in carcinogenesis. However, the oncogenic cooperation between these two cascades in relationship to hepatocellular carcinoma (HCC) development remains undetermined. To investigate this issue, we generated a mouse model characterized by combined overexpression of activated forms of AKT and neuroblastoma Ras viral oncogene homolog (N-Ras) protooncogenes in the liver by way of hydrodynamic gene transfer. The molecular mechanisms underlying crosstalk between AKT and N-Ras were assessed in the mouse model and further evaluated in human and murine HCC cell lines. We found that coexpression of AKT and N-Ras resulted in a dramatic acceleration of liver tumor development when compared with mice overexpressing AKT alone, whereas N-Ras alone did not lead to tumor formation. At the cellular level, concomitant up-regulation of AKT and N-Ras resulted in increased proliferation and microvascularization when compared with AKT-injected mice. Mechanistic studies suggested that accelerated hepatocarcinogenesis driven by AKT and N-Ras resulted from a strong activation of mammalian target of rapamycin complex 1 (mTORC1). Furthermore, elevated expression of FOXM1/SKP2 and c-Myc also contributed to rapid tumor growth in AKT/Ras mice, yet by way of mTORC1-independent mechanisms. The biological effects of coactivation of AKT and N-Ras were then recapitulated in vitro using HCC cell lines, which supports the functional significance of mTORC1, FOXM1/SKP2, and c-Myc signaling cascades in mediating AKT and N-Ras-induced liver tumor development. CONCLUSION: Our data demonstrate the in vivo crosstalk between the AKT and Ras pathways in promoting liver tumor development, and the pivotal role of mTORC1-dependent and independent pathways in mediating AKT and Ras induced hepatocarcinogenesis.