Abstract

Cigarette fastball has been immediately implicated in the disease pathogenesis of a overplus of unlike human cancer subtypes, including front cancers. The prevail view is that cigarette fume acts as a mutagen and DNA damaging agent in normal epithelial cells, driving tumor initiation. however, its electric potential damaging metabolic effects on the normal stromal microenvironment have been largely ignored. here, we propose a modern mechanism by which carcinogen-rich cigarette smoke may promote cancer growth, by metabolically “ fertilizing ” the server microenvironment. More specifically, we show that cigarette smoke exposure is indeed sufficient to drive the onset of the cancer-associated fibroblast phenotype via the initiation of DNA damage, autophagy and mitophagy in the tumor stroma. In turn, cigarette smoke exposure induces premature aging and mitochondrial dysfunction in stromal fibroblasts, leading to the secretion of high-octane mitochondrial fuels, such as L-lactate and ketone bodies. Hence, cigarette smoke induces catabolism in the local microenvironment, immediately fueling oxidative mitochondrial metabolism ( OXPHOS ) in neighboring epithelial cancer cells, actively promoting anabolic tumor growth. unusually, these autophagic-senescent fibroblasts increased breast cancer tumor growth in vivo by up to 4-fold. importantly, we show that cigarette smoke-induced metabolic reprogramming of the fibroblastic stroma occurs independently of tumor neo-angiogenesis. We discuss the possible implications of our current findings for the prevention of aging-associated human diseases and, particularly, park epithelial cancers, as we show that cigarette smoke can systemically accelerate aging in the server microenvironment. last, our current findings are consistent with the idea that cigarette smoke induces the “ reverse Warburg impression, ” thereby fueling “ two-compartment tumor metamorphosis ” and oxidative mitochondrial metamorphosis in epithelial cancer cells. Keywords:

carcinogens, cigarette smoke, cancer prevention, autophagy, senescence, premature aging, mitochondrial dysfunction, lactate, ketone bodies, breast cancer, tumor growth, microenvironment

Introduction

Cigarette smoking and/or tobacco consumption has been linked to about one-third of all cancer-related deaths. 1 – 5 Although cigarette smoke is most often associated as a caustive agentive role in human lung cancers, it besides distinctly has permeant systemic effects. For exemplar, cigarette smoke increases the risk for the growth of many different types of homo cancers, including head and neck, bladder, pancreatic, abdomen, liver, ovarian, colon, prostate gland and breast cancers. 1 – 5 During the twentieth hundred, it has been estimated that tobacco use contributed importantly to the premature deaths of about 100 million people global, and it is still considered the unmarried most preventable cause of previous death. Cigarette smoke contains a complex assortment of > 7,000 chemicals and toxic substances and > 70 known mutagens or carcinogens, most notably the polycyclic aromatic hydrocarbons, such as benzo ( a ) pyrene ( BAP ) ( www.cancerresearchuk.org/cancer-info/healthyliving/smokingandtobacco ). early examples of cancer-causing agents included are : pitch, arsenic, benzene, cadmium, formaldehyde, polonium-210, chromium, 1,3-butadiene, nitrosamines, propenal, acetaldehyde, hydrazine and other heavy metals ( nickel, cobalt and beryllium ). other metabolic poisons included are : hydrogen nitrile, carbon monoxide, nitrogen oxides, ammonia, sulphur dioxide, hydrogen sulfide, pyridine and toluene. last, cigarette smoke besides contains the dangerous addictive drug nicotine. Despite a wealth of information on how cigarette fastball directly affects whole animal models and versatile epithelial and endothelial cellular telephone types, relatively short is known regarding how cigarette smoke exposure affects the stromal microenvironment. here, we show that cigarette smoke exposure induces autophagy and previous ripening ( aging ) in commemorate human stromal fibroblasts. These autophagic-senescent fibroblasts then acquire the ability to metabolically promote tumor increase in a paracine fashion. This provides a newly mechanism to understand why tobacco fastball exposure promotes both tumor trigger and progress, by providing high-octane mitochondrial fuels to facilitate tumor growth and metastatic progress .

Discussion

recently, we showed that autophagic and/or aging cancer-associated fibroblasts ( CAFs ) promote tumor increase in preclinical animal models when co-injected with human breast cancer cell lines. 6, 13 We have termed this phenomenon the “ autophagic tumor stroma model of cancer ” or “ two-compartment tumor metabolism. ” 6, 7, 13 – 18 We have demonstrated that cancer cells release ROS into the tumor microenvironment. In plow, ROS initiates autophagy and mitophagy in neighbor fibroblasts. 14 – 17 These events inhibit mitochondrial metabolism, driving aerobic glycolysis in autophagic and aging fibroblasts. 13 consequently, these fibroblasts now begin to secrete energy-rich molecules ( L-lactate, ketone bodies and glutamine ) into the tumor microenvironment. 7, 15, 16 Cancer cells then consume these secreted energy-rich molecules via mitochondrial oxidative phosphorylation ( OXPHOS ). 18 This stromal-epithelial metabolic coupling produces sufficient energy that supports cancer cells to sustain proliferation and invasion. here, we examined if CSE alters cancer-associated fibroblast metamorphosis and breast cancer tumor emergence. Our data demonstrate that CSE-treated fibroblasts display an up to 31.5-fold increase in fibroblasts convinced for the agedness marker β-Gal. We show that this was due to the activation of the DNA damage answer and the p53-p21-pRb nerve pathway. Furthermore, an elevation in agedness was associated with increase markers of autophagy and mitophagy. Our immunoblot analyses showed that multiple exposures to CSE inhibited the expression of mitochondrial OXPHOS complexes. coherent with our current findings, van five hundred Toorn et. al., showed that CSE blocks the mitochondrial respiratory chain and ATP production in lung fibroblasts. 19 frankincense, CSE exposure should drive hTERT-BJ1 fibroblasts toward glycolysis and ketogenesis. As bode, we observed that CSE-treated fibroblasts displayed a significant increase in L-lactate and ketone output. similarly, CSE-treated esophageal epithelial cells display higher glucose pulmonary tuberculosis and lactate production. 20 We besides co-injected CSE-treated fibroblasts with breast cancer cells. At day 22, the tumors were surgically excised, weighed and measured using calipers. unusually, CSE-treated fibroblasts increased tumor increase by up to 4-fold, without any significant increases in tumor angiogenesis. Since we show that cigarette smoke induces previous aging ( aging ) in stromal fibroblasts, our current studies may besides have implications for understanding how cigarette fume systemically induces accelerated aging in the host microenvironment ( ). This provides a novel experimental model for identifying new therapeutic interventions for the prevention of epithelial cancers and, potentially, other aging-associated diseases that are due to increased oxidative stress and accumulated DNA damage .An external file that holds a picture, illustration, etc.
Object name is cc-12-818-g6.jpgOpen in a separate window finally, our holocene studies show that both genetic and environmental factors facilitate the generalization of the cancer-associated fibroblast phenotype by common mechanism ( s ) ( ). For example, breast cancer-derived epithelial cells [ sporadic or familial ( BRCA1 ( −/− ) ] induce the cancer-associated fibroblast phenotype by driving oxidative stress and Warburg-like metamorphosis in the stromal microenvironment. 14, 21 – 23 In addition, ethyl alcohol exposure 24 and cigarette smoke ( this report ) can induce the cancer-associated fibroblast phenotype by the lapp metabolic mechanism ( s ) ( DNA damage, oxidative try and autophagy/mitophagy ), explaining how both genic and behavioral factors act in concert to “ fuel ” anabolic tumor growth and mitochondrial OXPHOS in cancer cells. Published clinical studies with Metformin ( a mitochondrial “ poison ” ) provide the necessity proof-of-principle that targeting cancer cell mitochondria can confer significant cancer chemo-prevention ( see referee. within 24 – 29 ) .An external file that holds a picture, illustration, etc.
Object name is cc-12-818-g7.jpgOpen in a separate window

Materials and Methods

Materials, cell lines and culture media

Human commemorate fibroblasts ( hTERT-BJ1 ) and human triple-negative breast cancer cells ( MDA-MB-231 ) were cultured in Dulbecco ’ s modified Eagle ’ south medium ( DMEM ), supplemented with 10 % fetal bovine serum in a 37°C humidified standard atmosphere containing 5 % CO2, unless otherwise noted. Antibodies were purchased from commercial sources : anti-phospho-H2AX ( 2577, Cell Signaling ) ; anti-phospho-RB ( ab47763, Abcam ) ; anti-BNIP3 ( ab65874, Abcam ) ; anti-LAMP2 ( sc-18822 ; Santa Cruz Inc. ) ; anti-LC3 A/B ( ab58610, Abcam ) or anti-LC3β ( sc-28266, Santa Cruz Inc. ) ; anti-p21 ( sc-0911, Santa Cruz Inc. ) ; anti-p53 ( OP43, Calbiochem ) ; anti-p16 ( sc-759, Santa Cruz Inc. ) ; anti-β actin ( A5441, Sigma ) ; anti-OXPHOS ( MA601, Mitoscience ) ; anti-AMPK ( 2532 ; Cell Signaling ).

Preparation of the cigarette smoke extract (CSE)

The CSE readiness was as previously described, 30 with minor modifications. Briefly, 40 milliliter of one puff was drawn from a lighted cigarette ( trickle cigarettes ; Marlboro Red containing 16 magnesium of pitch and 1.2 milligram of nicotine per cigarette ; Marlboro, Philip Morris ). Using a tripartite stopcock, the pot was drawn and dissolved vigorously into a 60-ml syringe, containing 10 milliliter of arrant media. Each cigarette was exhausted by 7–10 puffs and dissolved in 10 ml of complete media. For each treatment, the CSE-media was prepared fresh ( no more than 30 min ) and filtered through a 0.22 μm filter. The percolate media was considered as a 100 % CSE standard .

Immunoblotting

Cell protein lysates were obtained by cellular telephone scraping with lysis buffer ( 10 millimeter Tris, ph 7.5, 150 millimeter NaCl, 1 % Triton X-100 and 60 millimeter n-octylglucoside ) containing protease inhibitors ( Boehringer Mannheim ). Samples were incubated on a rotating platform at 4°C and were then centrifuged at 12,000 × gigabyte for 10 min ( at 4°C ) to remove insoluble debris. Protein concentrations were determined using the BCA reagent ( Pierce ). Samples were then separated by SDS-PAGE ( 10 % acrylamide ) and transferred to nitrocellulose. All subsequent moisten buffers contained 10 millimeter Tris, ph 8.0, 150 millimeter NaCl, 0.1 % Tween 20, which was supplemented with 5 % nonfat dry milk for the jam solution and 1 % bovine serum albumin ( Sigma ) for the antibody dilutant. horseradish peroxidase-conjugated secondary antibodies were used to visualize bound primary antibodies with an ECL signal detection kit ( Pierce ) .

Lactate assay

L-lactate levels were assessed according to the manufacturer ’ mho instructions using the EnzyChromTM L-Lactate Assay Kit ( big cat # ECLC-100, BioAssay Systems ). After 4 days of CSE treatment, 1.2 × 105 cells were seeded in 12-well plates in 10 % CSE containing media. The next day, the media was switched to phenol-free DMEM with 2 % FBS containing 10 % CSE. As control, untreated cells were processed in parallel. After 48 hydrogen, the media was collected, and the concentration of L-lactate was measured. Results were normalized for full cellular telephone number .

Ketone body assay

The media collected for the lactate assay was used to measure the ketone concentration. Ketones concentration was measured according the manufacturer ’ s instructions using the β-hydroxy-butyrate ( β-HB ) Assay Kit ( Biovision, # K632 ). Results were normalized for total cell issue .

Senescence assay

Cells were plated into 6-well plates in complete media. then, cells were treated with CSE every 2 days for sum of 6 days. At day 6, cells were fixed and incubated with a β-galactosidase staining solution ( Cell Signaling, # 9860 ) overnight at 37°C in a dry incubator without CO2. To measure the average of β-gal-positive cells, using an invert microscope, the count of stained cell was divided over the full number of cells in five random fields .

Xenograft studies

All animals were maintained in a pathogen-free environment/barrier adeptness, under National Institutes of Health ( NIH ) guidelines. All animal protocols were approved by the Institutional Animal Care and Use Committee ( IACUC ). Tumor cells ( MDA-MB-231 ; 1 × 106 cells ) were co-injected with hTERT-BJ1 fibroblasts ( 6 × 105 cells ) in 100 μl of sterile PBS into the flanks of athymic nude shiner ( NCRNU ; Taconic Farms ; 6–8 weeks of historic period ). Mice were then sacrificed at 22 d post-injection ; tumors were surgically excised to determine their system of weights and volume ( using electronic calipers ). tumor volumes were calculated using the formula V = a b2/2, where V is the tumor volume, a is the length of the long axis, and boron is the duration of the short-circuit bloc .

Angiogenesis quantification

To quantify tumor angiogenesis, CD31-positive vessels were enumerated in 4–6 fields within the central sphere of each tumor using a 20× aim lens and an eyepiece grid ( 0.25 mm2 per field ). The sum numbers of vessel per unit area was calculated using ImageJ, and the datum was represented graphically .

Statistical analysis

statistical meaning was examined by Student ’ s t-test. Values of p < 0.05 were considered significant .

Acknowledgments

F.S. was the recipient role of a Young Investigator Award from the Breast Cancer Alliance. U.E.M. was supported by a Young Investigator Award from the Margaret Q. Landenberger Research Foundation. Funds were besides contributed by the Margaret Q. Landenberger Research Foundation ( to M.P.L. ). This work was besides supported, in depart, by a Centre grant in Manchester from Breakthrough Breast Cancer in the UK and an Advanced ERC Grant from the European Research Council. besides, these developments were made possible through the resources of Thomas Jefferson University .

Submited

01/18/13

Disclosure of Potential Conflicts of Interest

No electric potential conflicts of interest were disclosed .

Footnotes

previously published on-line : www.landesbioscience.com/journals/cc/article/23722

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