Originally published as JCO Early Release 10.1200/JCO.2005.01.4910 on October 11 2005

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Macrophage and Mast-Cell Invasion of Tumor Cell Islets Confers a Marked Survival Advantage in Non–Small-Cell Lung Cancer

Tomas J. Welsh, Ruth H. Green, Donna Richardson, David A. Waller, Kenneth J. O'Byrne, Peter Bradding

From the Department of Infection, Immunity, and Inflammation; Department of Cancer Studies and Molecular Medicine, University of Leicester Medical School; Department of Cardiothoracic Services, University Hospitals of Leicester National Health Service Trust, Glenfield Hospital, Leicester; Thoracic Oncology Research Group, St James's Hospital and Trinity College, Dublin, Ireland

Address reprint requests to Peter Bradding, MD, Department of Respiratory Medicine, Glenfield Hospital, Leicester, LE3 9QP, United Kingdom; e-mail: pbradding{at}hotmail.com.

	ABSTRACT

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PURPOSE: The role played by the innate immune system in determining survival from non–small-cell lung cancer (NSCLC) is unclear. The aim of this study was to investigate the prognostic significance of macrophage and mast-cell infiltration in NSCLC.

METHODS: We used immunohistochemistry to identify tryptase⁺ mast cells and CD68⁺ macrophages in the tumor stroma and tumor islets in 175 patients with surgically resected NSCLC.

RESULTS: Macrophages were detected in both the tumor stroma and islets in all patients. Mast cells were detected in the stroma and islets in 99.4% and 68.5% of patients, respectively. Using multivariate Cox proportional hazards analysis, increasing tumor islet macrophage density (P < .001) and tumor islet/stromal macrophage ratio (P < .001) emerged as favorable independent prognostic indicators. In contrast, increasing stromal macrophage density was an independent predictor of reduced survival (P = .001). The presence of tumor islet mast cells (P = .018) and increasing islet/stromal mast-cell ratio (P = .032) were also favorable independent prognostic indicators. Macrophage islet density showed the strongest effect: 5-year survival was 52.9% in patients with an islet macrophage density greater than the median versus 7.7% when less than the median (P < .0001). In the same groups, respectively, median survival was 2,244 versus 334 days (P < .0001). Patients with a high islet macrophage density but incomplete resection survived markedly longer than patients with a low islet macrophage density but complete resection.

CONCLUSION: The tumor islet CD68⁺ macrophage density is a powerful independent predictor of survival from surgically resected NSCLC. The biologic explanation for this and its implications for the use of adjunctive treatment requires further study.

	INTRODUCTION

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Non–small-cell lung cancer (NSCLC) accounts for 80% of all lung cancers, and is responsible for more deaths from cancer than any other tumor type in the Western world.¹ Surgical resection offers the only hope of cure, and yet even in patients with early (stage IA) tumors, the 5-year disease-free survival after apparently curative surgery is only 67%.² This indicates that metastasis occurs early in the course of the disease in many patients. It is therefore crucial that the factors associated with tumor dissemination are delineated in order to help with appropriate patient selection for surgery. Furthermore, knowing which patients will have a poor outcome could help target additional but relatively toxic therapy such as adjuvant chemotherapy to those who most need it.

Virtually all tumors arise within an immune-permissive environment associated with upregulation of humoral immune responses, a relative suppression of cell-mediated immunity, and the production of growth and cell-survival factors that induce angiogenesis and inhibit apoptosis.³ Most tumors have been shown to contain a lymphoreticular infiltrate, which was long thought to represent the host response to the malignancy. However, many studies have suggested that the immune infiltrate may actually benefit the tumor by producing a pro-tumor microenvironment.⁴

Both macrophages and mast cells form an important part of this immune-cell infiltrate and are found in virtually all malignancies (reviewed in Bingle, Brown, and Lewis⁴ and Dimitriadou and Koutsilieris⁵). They have been shown to produce both positive and negative effects on tumor growth depending on the tumor microenvironment and have been shown to correlate with both favorable and worse prognoses.^4,5 Only a few studies have looked for a link between macrophage and mast-cell tumor infiltration and patient survival in NSCLC, but again the evidence is conflicting, and no clear consensus has prevailed.^6-12 These discrepancies appear to reflect differences in the number, grade, stage, and size of tumors included in the various studies, and the methods used to assess macrophage and mast-cell infiltration, which have varied considerably. In particular, the microanatomical localization of macrophages and mast cells within the tumor has not been taken into account. Given the critical importance of the microenvironment in determining leukocyte function and phenotype, this may influence profoundly the nature of the immunocyte-tumor interaction.

The aim of this study was therefore to assess the prognostic significance of tumor-associated macrophages and mast cells in 175 patients with surgically resected NSCLC, paying particular attention to the tissue microlocalization of these cells.

	PATIENTS AND METHODS

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Study Population
The study was approved by the Leicestershire Research Ethics Committee. The tissue specimens evaluated were from 175 patients with NSCLC who had undergone resection with curative intent at the University Hospitals of Leicester National Health Service Trust (Leicester, United Kingdom). Two cohorts of consecutive patients were analyzed, one dating from 1991 to 1994 and the second from January to December 1999. Of the 175 patients studied, 116 were men. Average age at surgery was 67.7 years (standard deviation, 9.3; range, 39 to 91 years). Full clinicopathologic information was gathered before and after surgery, including patient characteristics, treatment, combined clinical and surgical staging results (preoperative staging by computed tomography scan, selective mediastinoscopy, and systematic lymph node sampling at operation), histologic subtype, tumor grade, and survival data.

Immunohistology
The specimens studied were formalin fixed and paraffin embedded. Only blocks containing the advancing edge of the primary tumor were evaluated. Tissue sections of 5 µm thickness were cut onto glass slides then de-waxed in xylene and rehydrated through graded alcohols. Antigen retrieval was carried out using trypsin (1 mg in 1mL deionized water at 20°C for 6 minutes). Mouse antihuman mast cell tryptase monoclonal antibody (mAb; clone AA1, Dakocytomation Ely, Cambridgeshire, United Kingdom) was used as a specific marker for mast cells,¹³ and mouse antihuman macrophage CD68 mAb (clone PGM1; Dakocytomation, Ely, Cambridgeshire, United Kingdom) was used as a specific marker for macrophages.¹⁴ Immunostaining for tryptase and CD68 was performed using the Envision double-stain kit (Dakocytomation) according to the manufacturer's instructions. Tryptase was developed with peroxidase and 3,3'-diaminobenzidine tetrahydrochloride (brown reaction product), and CD68 with alkaline phosphatase and fast red (red reaction product). Sections were then counterstained with hematoxylin and mounted in an aqueous mounting medium (BDH Chemicals Ltd, Poole, United Kingdom). Appropriate isotype controls were performed where the primary antibodies were replaced by irrelevant mouse mAb of the same isotype and at the same concentration as the specific primary mAb.

Analysis and Validation of Immunostaining
Analysis was performed blind with respect to the clinical outcome. The five most representative high-power fields (x400) per slide were manually selected using an Olympus BX50 microscope (Olympus, Southall, United Kingdom). The respective areas of stroma and of tumor-cell islets were then measured at x400 magnification using Scion image analysis software (Based on National Institutes of Health Image for Macintosh, modified for Windows [Scion Corp, Frederick, MD]). The number of nucleated mast cells and macrophages in each area was then counted manually and expressed as cells/mm² of stroma or tumor islets, and also the ratio of tumor islet counts to stromal counts. Analysis was carried out initially with 20 cases, which were then re-examined 2 weeks later; the two sets of data were then compared to assess the repeatability and, hence, the validity.

Statistical Analysis
Statistical analyses were carried out using the Statistical Package for the Social Sciences (SPSS, v. 12.0; SPSS Inc, Chicago, IL). For categoric analysis, the median value was used as a cut point to dichotomise the series. The ² test was used to test for relationships between categoric variables, and the Mann-Whitney nonparametric test was used to compare categoric with continuous variables. Kaplan-Meier survival curves were used to look for correlations with survival and were compared with the use of the log-rank statistic. A multivariate Cox proportional hazards model was used to estimate adjusted hazard ratios, 95% CIs and to identify independent prognostic factors. A formal test to detect departure from the proportional hazards assumption was carried out by comparing hazard ratios in different intervals of time before carrying out Cox regression. For the above comparisons, P < .05 was considered statistically significant.

	RESULTS

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Patient Demographics
Of the 175 patients studied, 118 had died at the time of analysis, and 88% of these deaths were cancer related. Thirty-day mortality was 4%. For the purposes of the study, deaths within the first 60 days of surgery (n = 13) were excluded, leaving 162 cases for analysis. Eighty-five tumors were squamous, 51 adenocarcinoma, 16 large cell, and 10 other. Seventy-nine were stage 1, 44 stage II, 35 stage IIIa, and four stage IIIb or IV. Seven patients had additional postoperative chemotherapy and 33 had additional radiotherapy, 28 of whom had it for later palliation. Neither had any effect on survival. The overall 5-year survival rate was 30.8%.

Validation of Analysis
Clear and distinguishable staining was evident for both CD68 and mast-cell tryptase (Fig 1A-1D). Appropriate isotype controls were negative. In order to assess the validity of the method, area measurements and cells counts were repeated and intraclass correlation coefficients calculated. Good correlations were found for both: 0.996 (95% CI, 0.995 to 0.997; P < .0001) and 0.995 (95% CI, 0.993 to 0.997; P < .0001), respectively. Depending on availability, either one or two tissue blocks from each patient was used. The intraclass correlation between the density of the cells in one block compared with a second block when available was also high at 0.946 (95% CI, 0.937 to 0.953; P < .0001).

View larger version (146K): [in this window] [in a new window]   Fig 1. Immunohistology demonstrating the presence of CD68+ macrophages (red) in (A) tumor stroma and (B) tumor islets, and the presence of tryptase+ mast cells (brown) in (C) tumor stroma and (D) tumor islets.

Clinical Outcome
Scatter plots of the raw data of cell density versus survival are shown in Figure 2. Spearman's rank correlation coefficient was calculated to assess any potential relationship with survival using the data only from deceased individuals (n = 118). An inverse relationship between survival and stromal macrophage density was present (r_s = –0.353; P < .01), as was a direct relationship between tumor cell islet macrophage density and survival (r_s = 0.581; P < .01). With respect to mast cells, no relationship between stromal mast-cell count and survival was suggested (r_s = –0.089; P = .26). However the scatter plot of tumor cell islet mast-cell density and survival did suggest a direct relationship (r_s = 0.293; P < .01).

View larger version (30K): [in this window] [in a new window]   Fig 2. Raw data of macrophage and mast-cell counts plotted against survival in days in the different tumor compartments. (A) Stromal macrophages, (B) islet macrophages, (C) islet/stromal macrophage ratio, (D) stromal mast cells, (E) islet mast cells, and (F) islet/stromal mast-cell ratio. Open circles demonstrate patients still alive, closed circles those deceased.

Kaplan-Meier Survival Analysis
For further analysis, the data were divided into two groups above and below the median cell-count values. Kaplan-Meier survival curves were then plotted to investigate further the association with survival (Fig 3). The log-rank statistic was used to compare survival rates. There was an inverse association between survival and stromal macrophage density (P = .011), and striking positive associations between survival and both tumor islet-cell macrophage density (P < .0001) and tumor macrophage islet/stromal ratio (P < .0001). Significant but less marked positive associations between survival and both tumor islet-cell mast-cell density (P = .005) and islet/stromal mast-cell ratio (P = .002) were also found. Table 1 shows the survival rate at 5 years and median survival associated with the data. Of particular note are the tumor-cell islet macrophage density and the islet/stromal macrophage ratio. In those patients with a tumor-cell islet macrophage density above the median, 5-year survival was 52.9% compared with 7.7% in those below the median, and median survival was 2,244 days compared to 334 days, respectively. For tumor islet mast cells and the islet/stromal mast-cell ratio, similar but less marked associations were found, with 40% 5-year survival above the median versus 22% below the median, and median survival increased three-fold. Similar differences in survival with respect to macrophage and mast-cell counts were also evident within tumor stages (Table 2; Fig 4).

View larger version (26K): [in this window] [in a new window]   Fig 3. Kaplan-Meier actuarial survival curves for stromal macrophage density, islet macrophage density, islet/stromal macrophage ratio, stromal mast-cell density, islet mast-cell density, and the islet/stromal mast-cell ratio. Data were dichotomized at the median value for each parameter. (A) Stromal macrophages; (B) tumor islet macrophages; (C) islet/stromal macrophage ratio; (D) stromal mast cells; (E) islet mast cells; (F) islet/stromal mast-cell ratio.

View larger version (27K): [in this window] [in a new window]   Fig 4. Kaplan-Meier actuarial survival curves for each tumor stage dichotomized at the overall median value for the islet macrophage density.

View larger version (17K): [in this window] [in a new window]   Fig 5. Kaplan-Meier actuarial survival curves stratified according to the complete or incomplete surgical resection and dichotomized at the median value of the islet/stromal macrophage ratio. (1) Complete resection, less than median macrophage ratio; (2) complete resection, greater than median macrophage ratio; (3) incomplete resection, less than median macrophage ratio; (4) incomplete resection, greater than median macrophage ratio.

Only those variables that were associated with survival at a significance of P < .1 were included in the multivariate analysis. Significant independent prognostic indicators are summarized in Table 4. Of note, both tumor-cell islet macrophage density (P < .001), and macrophage ratio (P < .001) emerged as independent favorable prognostic indicators. Mast-cell islet/stromal ratio also emerged as an independent favorable prognostic indicator (P = .034). Stromal macrophage density (P < .001) was an independent prognosticator of reduced survival. Tumor islet mast-cell density as a continuous variable was not an independent prognostic indicator, but if tumor islet mast cells were recorded as present or absent, the presence of tumor-cell islet mast cells then emerged as an independent prognostic indicator (P = .018). Resection status was included in the Cox model but was not an independent predictor of survival (P = .058).

	DISCUSSION

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Several previous studies in NSCLC and other tumor types have addressed the same question but the results have been conflicting.^4-12 This appears to reflect the different methods of assessment used, and in some cases the small sample size. For example, Chen et al⁹ reported that tumor-associated macrophages are associated with worse prognosis in NSCLC, but counted both stroma and tumor together. Toomey et al¹⁵ found no association with macrophage count and outcome in NSCLC, but again counted both tumor infiltrating macrophages and adjacent stroma together. Johnson et al⁷ found no association with stromal or tumor macrophages, but assessment was semiquantitative and numbers studied relatively small. In contrast, Ohno et al¹⁶ specifically counted macrophages within gastric carcinoma stroma and islets, and found that tumor islet–infiltrating macrophages were associated with increased survival. In our study, particular attention was paid to counting macrophages and mast cells within the NSCLC stroma versus the islets. The importance of this is demonstrated clearly by the strong inverse relationship evident between survival and stromal macrophage density, and the strong direct relationship between survival and islet macrophage infiltration. Thus with a macrophage islet density above the median, the 5-year survival is approximately seven times that of patients with a macrophage count below the median. In contrast, with a tumor stromal macrophage count above the median, survival is only half that compared with the group below the median. The findings indicate that the exact microanatomic localization of these inflammatory cells is critical in determining the relationship to prognosis.

As with macrophages, the relationship between numbers of tumor-infiltrating mast cells and survival in a variety of tumors is unclear.^5,10-12 We have found that in terms of stromal mast-cell numbers there was no significant association with survival. Stromal mast-cell counts, however, were relatively constant between patients, and when expressed as cells/mm², these figures were similar to those reported in normal bronchus.¹⁷ This however does not exclude a role for stromal mast cells in modifying tumor behavior, because their state of activation is more important in determining their role, and we cannot delineate this from the current study. Further work using electron microscopy to determine granule morphology, and study of cell function and phenotype in cells isolated from the tumor compared to normal lung parenchyma is required. In contrast to the data on stromal mast cells, a strong independent association was found between the presence of tumor cell islet mast cells and an improved prognosis suggesting they may in fact have a protective effect on tumor progression.

When resection status was stratified according to macrophage islet density above or below the median, we found that those patients with a high islet macrophage density survived much longer than those with a low islet macrophage density even if they had incomplete resection of their tumor. Patients with complete resection normally would be expected to have an extended survival time, but in the presence of a low macrophage islet/stromal ratio the median survival was only 325 days. In contrast, patients with an incomplete resection would normally be expected to have a short survival time, but in the presence of a high macrophage islet/stromal ratio the median survival was 2,143 days, and the 5-year survival rate 62.5%. Similar observations were made with respect to survival in stage IIIa disease with greater than median islet macrophages versus stage I and II with less than median islet macrophages. This is remarkable and supports the notion that a high tumor islet macrophage count limits the progression of the disease. Thus our data indicate that even in those patients with apparent stage I disease, the presence of a low tumor islet macrophage density indicates a high chance of metastatic spread at the time of surgery.

Macrophage islet/stromal ratio and tumor islet-cell macrophage density were inversely correlated with stage, suggesting that a larger number of macrophages in the tumor islets rather than the stroma is associated with a lower stage. This is very interesting and can be interpreted as showing that a higher proportion of tumor-cell islet macrophages reduces the local and systemic spread of the disease. An alternative explanation is that as a tumor evolves, the macrophage islet count drops. However, this is unlikely because the tumor islet counts predict improved survival independently in the multivariate analysis, and the relationship remains significant within tumor stages.

There are several potential biologic mechanisms that might explain our findings and are worthy of further study. A simple explanation is that stromal macrophages contribute to tumor stroma formation and angiogenesis, thus supporting tumor growth, whereas tumor cell islet macrophages are cytotoxic, and thus limit tumor growth. The phenotype of macrophages and mast cells is undoubtedly modified by their microenvironment, and there is evidence that this applies within tumors. For example, stromal macrophages are known to express matrix-degrading and -producing factors as well as proangiogenic factors,⁴ which would allow them to regulate stroma remodeling and promote neovascularization, thus supporting tumor growth. In prostate cancer, tumor-cell islet but not stromal macrophages express nitric oxide synthase and tumor necrosis factor-, both factors involved in tumor cell–killing mechanisms.¹⁸ Future work assessing stromal vessel counts in association with macrophage density, and analysis of other macrophage markers reported to stain cytotoxic macrophage populations^19,20 will help address these issues. In addition, macrophages can act as antigen-presenting cells to activate cytotoxic T cells. It has been found that the degree of CD8⁺ T-cell infiltration directly correlates with macrophage infiltration in gastric carcinoma, suggesting that macrophages play an important part in the activation of T cells and the subsequent tumor cell destruction.¹⁶ If we can understand fully the biologic mechanisms leading to tumor suppression by macrophages, then it might be possible to institute therapies that promote this.

There are important clinical implications from the identification that macrophage counts provide a powerful predictor of survival in NSCLC. In this series of 175 patients who were deemed resectable on current staging protocols, a significant percentage died rapidly and underwent apparently unnecessary surgery. This is especially relevant to stage IIIa disease, which carries a particularly poor prognosis. However, in those subjects with a greater than median tumor islet macrophage count for the series as a whole (> 131 CD68⁺ cells/mm²) survival was relatively good, and in fact better than in those patients with stage I disease but a low islet macrophage density (Fig 4). Thus, determining the islet macrophage density might be particularly useful when considering which stage IIIa patients to select for surgery. It will therefore be important to determine whether the same predictions regarding survival can be made from tumor within biopsies obtained at bronchoscopy. Similarly, when considering adjuvant therapy, it would be useful to target the patients most likely to benefit. At present, adjuvant chemotherapy for NSCLC improves survival for about 4% of patients treated²¹; thus 96% are exposed to potentially toxic treatment for no gain. Our data suggest that using the tumor islet macrophage density to single out those who require further treatment could be particularly useful. This issue is also important for the design of clinical trials of emerging therapies, because those subjects who are predicted to do well anyway may not gain much further benefit from chemotherapy, and so the signal from any trial might be diminished. In the short term, this could be assessed retrospectively from previous trials.

In summary we have demonstrated that the density of macrophages in tumor islets is a powerful predictor of survival in NSCLC. This has important implications for the targeting of surgery and adjuvant therapy, the design of future clinical trials of adjuvant therapy, and for our understanding of the immunopathobiology of this devastating disease.

	Authors' Disclosures of Potential Conflicts of Interest

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION Authors' Disclosures of... REFERENCES

 
The authors indicated no potential conflicts of interest.

	NOTES

 
Presented in part as an abstract at the British Thoracic Society Winter Meeting, London, United Kingdom, December 1-4, 2004, and at the American Thoracic Society Annual International Conference, San Diego, CA, May 20-25, 2005.

Terms in blue are defined in the glossary, found at the end of this issue and online at www.jco.org.

Authors' disclosures of potential conflicts of interest are found at the end of this article.

	REFERENCES

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION Authors' Disclosures of... REFERENCES

 
1. Bray F, Sankila R, Ferlay J, et al: Estimates of cancer incidence and mortality in Europe in 1995. Eur J Cancer 38:99-166, 2002

2. Mountain CF: Revisions in the International System for Staging Lung Cancer. Chest 111:1710-1717, 1997[Abstract/Free Full Text]

3. O'Byrne KJ, Dalgleish AG: Chronic immune activation and inflammation as the cause of malignancy. Br J Cancer 85:473-483, 2001[CrossRef][Medline]

4. Bingle L, Brown NJ, Lewis CE: The role of tumour-associated macrophages in tumour progression: Implications for new anticancer therapies. J Pathol 196:254-265, 2002[CrossRef][Medline]

5. Dimitriadou V, Koutsilieris M: Mast cell-tumor cell interactions: For or against tumour growth and metastasis? Anticancer Res 17:1541-1549, 1997[Medline]

6. Koukourakis MI, Giatromanolaki A, Kakolyris S, et al: Different patterns of stromal and cancer cell thymidine phosphorylase reactivity in non-small-cell lung cancer: Impact on tumour neoangiogenesis and survival. Br J Cancer 77:1696-1703, 1998[Medline]

7. Johnson SK, Kerr KM, Chapman AD, et al: Immune cell infiltrates and prognosis in primary carcinoma of the lung. Lung Cancer 27:27-35, 2000[CrossRef][Medline]

8. Takanami I, Takeuchi K, Kodaira S: Tumor-associated macrophage infiltration in pulmonary adenocarcinoma: Association with angiogenesis and poor prognosis. Oncology 57:138-142, 1999[CrossRef][Medline]

9. Chen JJ, Yao PL, Yuan A, et al: Up-regulation of tumor interleukin-8 expression by infiltrating macrophages: Its correlation with tumor angiogenesis and patient survival in non-small cell lung cancer. Clin Cancer Res 9:729-737, 2003[Abstract/Free Full Text]

10. Takanami I, Takeuchi K, Naruke M: Mast cell density is associated with angiogenesis and poor prognosis in pulmonary adenocarcinoma. Cancer 88:2686-2692, 2000[CrossRef][Medline]

11. Imada A, Shijubo N, Kojima H, et al: Mast cells correlate with angiogenesis and poor outcome in stage I lung adenocarcinoma. Eur Respir J 15:1087-1093, 2000[Abstract]

12. Nagata M, Shijubo N, Walls AF, et al: Chymase-positive mast cells in small sized adenocarcinoma of the lung. Virchows Arch 443:565-573, 2003[CrossRef][Medline]

13. Walls AF, Bennett AR, McBride HM, et al: Production and characterization of monoclonal antibodies specific for human mast cell tryptase. Clin Exp Allergy 20:581-589, 1990[CrossRef][Medline]

14. Falini B, Flenghi L, Pileri S, et al: PG-M1: A new monoclonal antibody directed against a fixative-resistant epitope on the macrophage-restricted form of the CD68 molecule. Am J Pathol 142:1359-1372, 1993[Abstract]

15. Toomey D, Smyth G, Condron C, et al: Infiltrating immune cells, but not tumour cells, express FasL in non-small cell lung cancer: No association with prognosis identified in 3-year follow-up. Int J Cancer 103:408-412, 2003[Medline]

16. Ohno S, Inagawa H, Dhar DK, et al: The degree of macrophage infiltration into the cancer cell nest is a significant predictor of survival in gastric cancer patients. Anticancer Res 23:5015-5022, 2003[Medline]

17. Bradding P, Roberts JA, Britten KM, et al: Interleukin-4, -5, and -6 and tumor necrosis factor-alpha in normal and asthmatic airways: Evidence for the human mast cell as a source of these cytokines. Am J Respir Cell Mol Biol 10:471-480, 1994[Abstract]

18. Shimura S, Yang G, Ebara S, et al: Reduced infiltration of tumor-associated macrophages in human prostate cancer: Association with cancer progression. Cancer Res 60:5857-5861, 2000[Abstract/Free Full Text]

19. Endress H, Freudenberg N, Fitzke E, et al: Infiltration of lung carcinomas with macrophages of the 27E10-positive phenotype. Lung Cancer 18:35-46, 1997[Medline]

20. Mahnke K, Bhardwaj R, Sorg C: Heterodimers of the calcium-binding proteins MRP8 and MRP14 are expressed on the surface of human monocytes upon adherence to fibronectin and collagen: Relation to TNF-alpha, IL-6, and superoxide production. J Leukoc Biol 57:63-71, 1995[Abstract]

21. The International Adjuvant Lung Cancer Trial Collaborative Group: Cisplatin-based adjuvant chemotherapy in patients with completely resected non-small-cell lung cancer. N Engl J Med 350:351-360, 2004[Abstract/Free Full Text]

Submitted February 23, 2005; accepted August 8, 2005.

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