Abstract P1-03-12: The ratio of omega-3 to omega-6 PUFAs impact cancer cell phenotype in the tumor microenvironment

Background: Studies have shown that obesity is associated with a worse breast cancer prognosis. Besides the effect of different stages of diagnosis and co-morbidities, recent data from our published in vitro and retrospective studies suggests that this phenomenon may occur because the obese state promotes a more aggressive cancer phenotype through the cyclooxygenase (COX-2) pathway and its production of prostaglandin E2 (PGE2). The metabolization of omega-3 fatty acids decreases the production of PGE2, and have been shown to have potential benefit to cancer patients by decreasing inflammation-related signaling. Our previous clinical trial showed mixed results in the effect of omega-3 PUFA supplements on PGE2 production in post-menopausal obese women. This led us to the hypothesis that the ratio of omega-3 to omega-6 PUFAs have differential effects on cell types within the tumor microenvironment, impacting cancer cell phenotype.

Approach: In vitro experiments, including wound-healing assays to determine motility, and clonogenic assays to determine overall survival, were performed to determine if exposure to higher ratios of omega-6 to omega-3 fatty acids lead to a more aggressive cancer phenotype. MCF-7 breast cancer cells were treated with the following fatty acid ratios of omega-6 (arachidonic acid (AA)) to omega-3 (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)): 46:1, 20:1, 10:1, and 1.3:1. The wound-healing assays showed greater motility with higher ratios of omega-6 to omega-3 fatty acids conditions and the clonogenic assays showed greater survival with the higher ratios.

Conclusion: These data indicate that lowering ratios of omega-6 to omega-3 fatty acids may lessen the aggressiveness of breast cancer cells and be beneficial to some patients. Studies are on-going to investigate the impact of PUFA ratios on cancer cell phenotype directly, including proliferation and invasion, as well as the indirect effects from modulation of the other cells within the tumor microenvironment, including the macrophages and adipocytes.

Citation Format: Winikka L, Quach D, Harlow B, Brenner A, Munoz N, Tiziani S, deGraffenried L. The ratio of omega-3 to omega-6 PUFAs impact cancer cell phenotype in the tumor microenvironment [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-03-12.

Abstract P3-07-10: Modulation of FASN under obese conditions

Introduction: Obesity is known to be associated with a worse breast cancer prognosis, in part through altering metabolism in cells of the tumor microenvironment. In particular, changes in metabolism associated with fatty acid utilization have been noted in not only breast cancer, but also several other cancer types. This includes changes to both expression and activity of the Fatty Acid Synthase enzyme (FASN), which is responsible for production of long chain fatty acids, including palmitate. These changes in long chain fatty acid production can modulate tumor behavior through modulation of energy utilization such as beta-oxidation, as well as plasma membrane modulation with phospholipids. Our previous studies have demonstrated that exposure to obese conditions induces significant changes in breast cancer cell proliferation. Additionally, obesity modulates activity of other cells within the tumor microenvironment, including adipocytes, which might influence the cancer cell itself. We hypothesize one particular mechanism that supports these changes is obesity-induced upregulation of FASN and that FASN may be a viable target to limit obesity-induced progression.

Methods and Results: FASN has been shown to promote cancer cell proliferation through generating fatty acid precursors required for cell proliferation, altering membrane fluidity, and activating oncogenic signaling pathways. To determine if modulation of FASN is an important mechanism by which obesity promotes disease progression, MCF-7 breast cancer cells and human pre-adipocyte cells (ASC) were exposed to 2% sera from obese postmenopausal women and 2% sera from non-obese (control) women. Preliminary quantitative PCR results demonstrated that exposure to the obese sera resulted in increased expression of FASN in both the cancer cells as well as the ASC. Current studies are on-going to determine if 1) FASN up-regulation results in increased long-chain and free fatty acid production in both the cancer and adipocyte cells, 2) whether changes in long chain and free fatty acid production results in altered metabolism and plasma membrane status and 3) whether targeting FASN with a new generation of FASN inhibitors currently being investigated in the clinic can modulate obesity-induced disease progression.

Conclusions: Our findings indicate that obesity promotes upregulation of FASN in several cells within the tumor microenvironment, including adipocytes and the cancer cell itself. We have also found that using a FASN inhibitor is effective in limiting cancer cell viability and proliferation. Our on-going studies will confirm if this is an important mechanism by which obesity promotes disease progression. Since FASN inhibitors are currently being investigated in the clinic, the results of these studies will provide a better understanding of how obesity alters the biology of the disease, and may identify a novel target for improving patient outcomes.

Citation Format: Pham T, Oberman A, Kim I, Lee G, Quach D, Galván G, Jolly C, Cavazos D, Brenner A, deGraffenried L. Modulation of FASN under obese conditions [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-07-10.

Abstract P4-04-03: Obesity-induced EMT in luminal A breast cancer cells

Introduction: Obesity is associated with a worse prognosis in breast cancer, including the less aggressive ER+ luminal A subtype, but the mechanisms by which it promotes disease progression are unclear, making treatment difficult. Obese breast cancer patients have a higher risk of a more aggressive disease compared to lean patients, which is associated with treatment resistance and metastasis. The mechanisms promoting obesity-driven metastasis are not understood, but several studies have indicated that obesity is associated with a “stem-like” phenotype. A “reprogramming” occurs, transforming stationary, epithelial cells to motile, malignant cells that exhibit a more aggressive phenotype than their stromal counterparts. Our data suggest that in vitro exposure of luminal A breast cancer cells to obese conditions may induce an epithelial to mesenchymal transition (EMT), which is characterized by a more stem-like phenotype, resistance to treatment (chemo, hormone and radiation), as well as greater metastatic potential. This has let us to hypothesize that one critical mechanism by which obesity promotes a more aggressive disease is through inducing an EMT reprogramming, resulting in a more stem-like phenotype.

Methods and Results: Both in vitro and translational approaches will be done to determine if obesity induces epigenetic reprograming associated with a more stem-like phenotype. MCF-7 ER+ breast cancer cells exposed to 2% sera from obese (BMI ≥ 30) postmenopausal women demonstrated a significant increase in expression of both SNAIL1 and TWIST transcription factors (9-fold and 4-fold, respectively) which are implicated in EMT and potentially stem-cell programming, compared to those exposed to sera from lean women. Current studies are underway to determine if this is observed in other ER+ luminal A cell lines, including T47D, and whether induced changes in these transcription factors results in changes in signaling pathways associated with EMT, including TGFβ, which can activate the PI3K–AKT, ERK MAPK, p38 MAPK and JNK pathways and WNT signaling, which promotes EMT by stabilizing β-catenin. Additionally, the luminal A cell lines will be assessed for changes in other factors known to modulate breast cancer cell programming, including KLF4, OCT4, SOX2, and NANOG.

Conclusions: Our earlier studies have demonstrated that obesity promotes a more aggressive disease even in luminal A disease. The mechanisms for this remain unclear. Our exciting preliminary findings suggest that obesity might induce a reprogramming of the luminal A well-differentiated cell to a more stem-like phenotype. Our results will lay an important foundation for understanding how obesity modulates breast cancer disease progression, whether this programming may provide therapeutic target to improve response and overall survival in the obese patient.

Citation Format: Hayden A, Quach D, Galvan G, Patodia R, Brenner A, deGraffenried L. Obesity-induced EMT in luminal A breast cancer cells [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-04-03.

Abstract P6-17-03: The importance of the ultimate ratio of Omega-6 to Omega-3 fatty acids in the efficacy of fish oil supplements in suppressing inflammation in obese postmenopausal women

Over the last decade, a large body of evidence has established that obesity is associated with a worse breast cancer prognosis for both pre- and postmenopausal women. There are several mechanisms which have been proposed for promoting this effect, including stage of diagnosis and co-morbidities, but more recent evidence suggests that the obese state is associated with changes in the biology of the disease, promoting a more aggressive phenotype. Our recently published in vitro and retrospective studies suggest that this is due, at least in part, through cyclooxygenase 2 (COX-2)-derived prostaglandin E2 (PGE2), and that interventions that suppress COX-2 PGE2 production may provide significant benefit for the obese ER+ patient in preventing many of the cancer-promoting effects associated with obesity. Omega-3 fatty acids have demonstrated anti-cancer benefit through multiple mechanisms, including suppression of inflammation-related signaling. DHA and EPA (omega-3 PUFAs found in fish oil) modulate inflammatory responses through COX-2 dependent and independent mechanisms. However, previous studies investigating the potential anti-cancer benefit of omega-3 PUFA and fish oil supplementation have produced mixed results, and none have focused specifically on the obese patient population.

To determine if supplementation with non-steroidal anti-inflammatory drugs (NSAIDs), including omega-3 fatty acids, can effectively suppress PGE2 production in the obese postmenopausal patient, we conducted a double-blind, prospective Phase 0, comparative, 30 day, non-interventional study with correlative biomarker endpoints. One hundred twenty (120) postmenopausal women without breast cancer were randomized to three arms 1. ASA 81mg po daily, 2. 1500mg of docosahexaoic acid (DHA) and 2500mg eicosapentanoic acid (EPA) given daily and 3. Combined ASA and DHA/EPA at above doses. Serum samples were collected prior to and on day 29 of taking the supplements. PGE2 levels in the pre- and post-supplement serum samples were analyzed in triplicate by ELISA and presented as the percentage of change between post- and pre-supplement levels. Of the women in Arm 2 (DHA + EPA only), only 55% demonstrated a significant suppression of PGE2 levels after 30 day of supplements, compared to those in Arm 1 (ASA), in which 80% demonstrated a significant response.

We anticipate that the omega-3 fatty acid supplements were not as effective in as large a population as the aspirin due to a failure to reach a critical ratio between circulating levels omega-6 and omega-3 fatty acids, which has been shown by our own group and others to be a key determinant of cellular response. Studies are on-going to analyze the PUFA levels in both the pre and post supplement serum samples, and pre-clinical studies are being conducted to determine if the ratio of omega-6 to omega-3 PUFAs modulates PGE2 production in several different cell types, including macrophages, adipocytes and the breast cell itself. These results will be critical for moving clinical studies utilizing these agents forward, both in terms of elucidating the mechanism mediating an effect, and also in identifying an accurate biomarker for monitoring compliance and response.

Citation Format: Quach D, Lengfelder L, Winnika L, Harlow B, Galvan G, Jolly C, Brenner A, deGraffenried L. The importance of the ultimate ratio of Omega-6 to Omega-3 fatty acids in the efficacy of fish oil supplements in suppressing inflammation in obese postmenopausal women [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-17-03.

Abstract P3-14-12: Phase 0 study evaluating COX2 inhibition on circulating PGE2 levels from obese subjects

Introduction: Obesity is associated with poor breast cancer outcomes in postmenopausal women in response to aromatase inhibitor therapy. Our prior studies have shown an association between reduced recurrence rate and use of cyclooxygenase-2 (COX-2) inhibiting non-steroidal anti-inflammatory drugs (NSAIDs) in obese breast cancer patients. The mechanism proposed was a decrease in prostaglandin E2 (PGE2) and reduced activation of the aromatase promote locally in the breast.

Methods: Postmenopausal women of varying body habitus were recruited at the CTRC in San Antonio and underwent randomized assignment to 1 of 3 arms: ASA 81mg daily, 1500mg of docosahexaenoic acid (DHA) and 2500mg eicosapentaenoic acid (EPA) given daily, or combined ASA and DHA/EPA. Sera were collected prior to and following 28 days of exposure, and cytokines including prostaglandin E2 were assessed via enzyme-linked immunosorbant assay (ELISA). Conditioned media was generated by exposing macrophages to patient sera in order to see if the patient sera induced PGE2 concentration in vitro.

Results: Thirty of the planned 120 subjects have completed assessment. No toxicity has been noted. In 71% of the patients, serum PGE2 levels decreased, but only 60% demonstrated concurrent decrease in serum PGE2 levels as well as macrophage PGE2 production, while almost all (88%) of the patients whose serum did not demonstrate a decrease in PGE2 levels also demonstrated no decrease in induced levels.

Conclusion: NSAIDs appear to effectively decrease circulating levels of PGE2 in most obese women. However, one third of the subjects did not demonstrate concurrent suppression of induced PGE2 from macrophages. These data suggest that circulating levels of PGE2 may not be reflective of local tumor microenvironment levels, and other pro-inflammatory circulating factors may be responsible for regulating local inflammatory responses. Final analysis will be completed and presented at the SABCS meeting.

Citation Format: Lengfelder L, Brenner A, Bowers L, Apte S, Galván G, Kist K, deGraffenried L. Phase 0 study evaluating COX2 inhibition on circulating PGE2 levels from obese subjects. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-14-12.

Abstract P4-09-02: Omega-3 ethyl esters suppress breast cancer growth by modulating inflammatory signaling

Introduction: Inflammation has been identified as a key contributor to breast cancer development. Both clinical and preclinical studies confirm a role for inflammatory mediators such as cytokines, interleukins, embedded immune cells and prostaglandins in promoting development of breast cancer. Elevated levels/activity of cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6) are correlated with a more aggressive disease. Omega-3 fatty acid (n-3) intake is correlated with an inverse risk for breast cancer development and improvement in prognostic markers. One key target of omega-3 fatty acids is the COX-2 enzyme. We hypothesize that one mechanism by which omega-3 fatty acids suppress breast cancer progression is through inhibition of inflammatory signaling.

Methods: The impact of omega-3 ethyl esters (n-3 EE), a component of some omega-3 supplements, on the viability of MCF-7 breast cancer cells grown in a pro-inflammatory environment was assessed by MTT analysis and on proliferation by cell counting. Supplementation of the growth media with IL-6 (10ng/mL) was used to simulate a pro-inflammatory environment. Changes in expression levels of key components of inflammatory pathways were assessed by Western blot analyses and quantitative PCR. Prostaglandin E2 (PGE2) levels were measured using ELISA assays.

Results: A significant suppression in IL-6-induced proliferation was observed when cells were exposed to physiological concentrations (20 uM) of n-3 EE for 96 hrs. Molecular analyses suggest that the suppression of the NF-kB/COX-2/PGE2 signaling axis was important for mediating this effect. These results are consistent with other studies using specific COX-2 inhibitors.

Conclusions: With their potent anti-inflammatory activity, n-3 EE may prove useful in reducing malignancy of breast cancer and also slow development of new breast cancers. Importantly, they appear to have none of the toxicities associated with pharmaceutical COX inhibitors (NSAIDs). Future studies are planned to incorporate nutraceutical compounds to standard therapy to improve efficacy and reduce associated side effects.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-09-02.

Abstract P1-06-01: Omega-3 Fatty Acids for Chemoprevention: NF-Kb as a Molecular Target in Both Pre and Post Menopausal High-Risk Breast Cancer Models

Genetic heterogeneity of human breast cancer has complicated treatment, prevention and therapeutic regimens in both clinical and personal care settings. With the recent advances in genetic analyses, human breast tumors are now segregated into four principle molecular subtypes: luminal A, luminal B, basal and HER2 overexpressors, each differing in their driver mutations, estrogen receptor status and dependence on specific cell signaling pathways to maintain growth and tumorigenicity. Omega-3 fatty acids have been shown in previous studies to be effective in modulating tumor growth in preclinical models of breast cancer, but epidemiological studies have been less clear regarding their efficacy as chemopreventive agents. Like many targeted therapies, we hypothesize that omega-3 fatty acids will be most effective against specific subtypes of disease, and it will be critical to identify these subtypes if these dietary agents are to be exploited most effectively. In this current study, the genetic diversity of breast cancer was represented by appropriate cell lines of matching molecular backgrounds and each class of breast cancer were subjected to exposures of omega-3 fatty ethyl esters derived from Lovaza®, an anti-hypertriglyceride medication that is currently under clinical evaluation as a chemopreventive for breast cancer. Previous studies have suggested that a target for omega-3 fatty acid modulation is the transcription factor NF-kB, a central key mediator of inflammation and cancer cell survival. Coined the single most important molecular machinery required for cancer initiation and promotion, NF-kB has been identified to play critical roles in all stages of breast cancer development. The omega-3 ethyl esters demonstrated suppression of NF-kB transcriptional activity, nuclear localization and overall function with high efficacy in the cell lines reflective of the luminal A, luminal B and basal subtypes, correlating with inhibition of proliferation and overall survival. Interestingly, among the panel of breast cancer subtypes, the aggressive HER2 overexpressing cell lines were resistant to the inhibitory effects of the omega-3 ethyl esters. One of the proposed mechanisms by which NF-kB is regulated is co-localization with IkB. siRNA knockdown assays suggest IkB involvement in the repression of NF-kB function by the omega-3 ethyl esters in the responding cell lines. Results from an ongoing clinical trial with omega-3 ethyl esters will help confirm if specific subtypes of breast cancers will be more effectively prevented using these agents, and whether NF-kB is the target by which they are mediating their anti-cancer effects. These studies are some of the first to use molecular profiles to identify potential responders and non-responders for dietary intervention and may provide better direction for future clinical studies evaluating the efficacy of diet and lifestyle in the preventive setting.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-06-01.

Curcumin Modulates Tamoxifen Response in Resistant Breast Cancer Cells

Despite significant improvement in both detection and treatment, breast cancer remains the second leading cause of cancer deaths for women in the United States. Tamoxifen is the most commonly used treatment for estrogen receptor positive (ER+) breast carcinoma, yet up to 50% of patients with metastatic disease present with de novo resistance to tamoxifen, and almost all patients will eventually become resistant to tamoxifen treatment. The mechanism(s) for this resistance appear to be largely dependent upon activation of growth factor signaling pathways. Aberrant activation of the PI3K/Akt and MAPK pathways and their cross talk with both the genomic and nongenomic activity of the ER is implicated in tamoxifen resistance. Breast cancer cell lines with constitutively activated Akt are characterized by high levels of the pro-survival transcription factor Nuclear Factor kappa B (NF-kB), estrogen-independent growth, and resistance to tamoxifen treatment. Studies have shown that curcumin, a polyphenol derived from the rhizome of the perennial herb Curcuma longa, is able to inhibit the activation of NF-kB, which is implicated as one mechanism by which breast cancer cells become resistant to tamoxifen treatment. Previous studies in our laboratory have demonstrated that inhibition of NF-kB is sufficient to sensitize MCF-7 cells that have constitutively activated Akt and elevated NF-kB levels to tamoxifen treatment. However, clinical NF-kB inhibitors such as Velcade generally involve suppression of the proteosome, leading to severe toxicities. Therefore, identification of alternative approaches for suppressing NF-kB activity in the absence of toxicity could prove beneficial for enhancing response to tamoxifen. In the present study, we assessed the efficacy of curcumin at inhibiting breast cancer cell proliferation and survival both as a single agent and in combination with tamoxifen in MCF-7 cells that expressed both “normal” levels of Akt (Control) activity as well as those that expressed the constitutively active form of Akt (myrAkt). As has been previously reported, curcumin treatment inhibited survival and proliferation in the Control MCF-7 cells, but importantly curcumin was also able to suppress survival and proliferation in the myrAKT MCF-7 cells. Curcumin and tamoxifen co-treatment was found to synergistically inhibit survival in myrAKT MCF-7 cells. These findings demonstrate that curcumin can sensitize myrAKT MCF-7 cells to tamoxifen treatment. This preliminary data suggests that the combination of natural NF-kB inhibitors such as curcumin with tamoxifen may be a viable strategy to either prevent tamoxifen resistant disease or to re-sensitize refractory disease to tamoxifen treatment.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3098.

mTOR Inhibition and Diet Induced Obesity in a Mouse Model of Postmenopausal Breast Cancer

Background:Breast cancer is the most common type of noncutaneous cancer among white women. It is more frequently diagnosed after menopause, and the majority of cases are estrogen receptor positive (ER+). Obesity is associated with poor prognosis, increasing risk by 50% in post-menopausal women, and correlates with shorter disease-free and overall survival. Unfortunately, the mechanism underlying the poorer outcomes in obese breast cancer patients is not known. The majority of ER+ tumors present with genomic ER activity; however, nongenomic ER activity can also occur, resulting in interaction with growth factor (GF) receptors.In the obese state nongenomic activity may be especially enhanced, promoting ER and GF signaling crosstalk, breast tumor cell growth and survival. Since Akt/mTOR signaling has been implicated in breast cancer, and obesity (through activation of GF signaling pathways) can activate this pathway, we hypothesized that the enhancement of tumor growth in response to obesity can be offset by mTOR inhibition. To test this we used a mouse model of postmenopausal breast cancer and investigated the effects of obesity (relative to lean and overweight phenotypes) with and without pharmacologic mTOR inhibition by RAD001.Methods:Ovariectomized C57BL/6 mice were randomized to diet regimens that induce either a lean, control (overweight), or a diet-induced obesity (DIO) phenotype. After 17 weeks on the diets, DIO mice were switched to the control diet and acclimated for 3 weeks. To determine diet-induced changes in adiposity, quantitative magnetic resonance (qMR) was performed at wk 18. At wk 21 mice were injected with syngeneic MMTV-Wnt-1 mammary tumor cells in the 4th mammary fat pad. Two weeks after tumor injection, the mice received RAD001 (10 mg/kg) or vehicle by oral gavage twice a week for 6 weeks.Tumor growth was measured weekly.Results:At week 17, mice in the DIO group were significantly heavier (42.8 g) than control (34.5 g) and lean mice (24.6 g) (p <0.001) and % fat was also higher (p<0.001) in DIO (54.5%) when compared to the control (42.2%) and lean (30.7%) groups.Tumor growth was different between the three diet regimens, confirming that dietary modulation directly influences MMTV-Wnt-1 tumor growth in a postmenopausal mouse model of breast cancer. DIO mice displayed significantly enhanced tumor growth (p<0.05) when compared to the control and lean mice. Overall, RAD001 was effective at decreasing tumor growth in all diet groups (p<0.01). However, the relative effect of RAD001 versus placebo was diminished in DIO mice compared to control and lean mice, suggesting obese mice may be partially resistant to RAD001. This resistance was overcome in the DIO mice by increasing the RAD001 dose to 15 mg/kg.Conclusion:Our results confirm that DIO increases tumor growth in the context of postmenopausal breast cancer. In addition, treatment with the mTOR inhibitor RAD001 reversed the mammary tumor enhancing effects of obesity (particularly at the higher dose of RAD001), further supporting mTOR as an important molecular target for breaking the obesity-breast cancer link.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5077.

Cellular expression of ceruloplasmin in baboon and mouse lung during development and inflammation

Ceruloplasmin (CP) is an important extracellular antioxidant and free radical scavenger. Although CP is expressed mainly in the liver, recent studies have identified the lung as another major site of CP synthesis. The sites and cell types that are responsible for CP expression in baboon and mouse lung are described. CP mRNA is detected in primordial bronchial epithelium in baboon fetuses by 60 days of gestation. At 140 days of gestation and thereafter, CP mRNA is found in airway epithelium and in the ductal cells of the submucosal glands. In developing and mature mice, CP mRNA is present in epithelial cells throughout the airway. In endotoxin-treated mice, the amount of CP mRNA increases several-fold in large airways but increases only moderately in small airways. This suggests that the high concentration of CP in the mucus lining of the upper airway, which serves to filter harmful substances, is particularly important during stressful conditions. Endotoxin treatment in mice also results in the induction of high levels of CP mRNA in a subset of alveolar wall cells. The data suggest that the airway epithelial cells are the major source of CP in the lung fluid and support ceruloplasmin's critical role in host defense against oxidative damage and infection in the lung.