Maintenance of both normal epithelial tissues and their malignant counterparts is supported by the host tissue stroma. The tumor stroma mainly consists of the basement membrane, fibroblasts, extracellular matrix, immune cells, and vasculature. Although most host cells in the stroma possess certain tumor-suppressing abilities, the stroma will change during malignancy and eventually promote growth, invasion, and metastasis. Stromal changes at the invasion front include the appearance of carcinoma-associated fibroblasts (CAFs). CAFs constitute a major portion of the reactive tumor stroma and play a crucial role in tumor progression. The main precursors of CAFs are normal fibroblasts, and the transdifferentiation of fibroblasts to CAFs is driven to a great extent by cancer-derived cytokines such as transforming growth factor-β. During recent years, the crosstalk between the cancer cells and the tumor stroma, highly responsible for the progression of tumors and their metastasis, has been increasingly unveiled. A better understanding of the host stroma contribution to cancer progression will increase our knowledge about the growth promoting signaling pathways and hopefully lead to novel therapeutic interventions targeting the tumor stroma. This review reports novel data on the essential crosstalk between cancer cells and cells of the tumor stroma, with an emphasis on the role played by CAFs. Furthermore, it presents recent literature on relevant tumor stroma- and CAF-related research in non-small cell lung cancer.

Purpose: The major value of prognostic markers in potentially curable non-small cell lung cancer (NSCLC) should be to guide therapy after surgical resection. In this regard, the patients' immune status at the time of resection may be important and also measurable. The immune system has paradoxical roles during cancer development. However, the prognostic significance of tumorinfiltrating lymphocytes is controversial.The aim of this study is to elucidate the prognostic significance of epithelial and stromal lymphocyte infiltration in NSCLC. Experimental Design: Tissue microarrays from 335 resected NSCLC, stage I to IIIA were constructed from duplicate cores of viable and representative neoplastic epithelial and stromal areas. Immunohistochemistry was used to evaluate the epithelial and stromal CD4 No such relation was noted for epithelial CD4 + cells. Furthermore, a low level of stromal CD8 + lymphocyte infiltration was associated with an increased incidence of angiolymphatic invasion (P = 0.032). In multivariate analyses, a high number of stromal CD8 + (P = 0.043) and CD4 + (P = 0.002) cells were independent positive prognostic factors for disease-specific survival.Conclusions: High densities of CD4 + and CD8 + lymphocytes in the stroma are independent positive prognostic indicators for resected NSCLC patients. This may suggest that these cells are mediating a strong antitumor immune response in NSCLC.

Purpose: Immunoscore is a prognostic tool defined to quantify in situ immune cell infiltrates, which appears to be superior to the tumor-node-metastasis (TNM) classification in colorectal cancer. In non-small cell lung cancer (NSCLC), no immunoscore has been established, but in situ tumor immunology is recognized as highly important. We have previously evaluated the prognostic impact of several immunological markers in NSCLC, yielding the density of stromal CD8 þ tumor-infiltrating lymphocytes (TIL) as the most promising candidate. Hence, we validate the impact of stromal CD8 þ TIL density as an immunoscore in NSCLC.Experimental Design: The prognostic impact of stromal CD8þ TILs was evaluated in four different cohorts from Norway and Denmark consisting of 797 stage I-IIIA NSCLC patients. The Tromso cohort (n ¼ 155) was used as training set, and the results were further validated in the cohorts from Bodo (n ¼ 169), Oslo (n ¼ 295), and Denmark (n ¼ 178). Tissue microarrays and clinical routine CD8 staining were used for all cohorts.Results: Stromal CD8 þ TIL density was an independent prognostic factor in the total material (n ¼ 797) regardless of the endpoint: disease-free survival (P < 0.001), disease-specific survival (P < 0.001), or overall survival (P < 0.001). Subgroup analyses revealed significant prognostic impact of stromal CD8 þ TIL density within each pathologic stage (pStage). In multivariate analysis, stromal CD8 þ TIL density and pStage were independent prognostic variables. Conclusions: Stromal CD8 þ TIL density has independent prognostic impact in resected NSCLC, adds prognostic impact within each pStage, and is a good candidate marker for establishing a TNM-Immunoscore.

In addition to malignant neoplastic cells, cancer tissues also include immune cells, fibroblasts, and endothelial cells, including an abundant collection of growth factors, proangiogenic mediators, cytokines, chemokines, and components of the extracellular matrix. The main physiological function of the immune cells is to monitor tissue homeostasis, to protect against invading pathogens, and to eliminate transformed or damaged cells. Between immune cells and malignant cells in the tumor stroma, there is in fact a complex interaction which has significant prognostic relevance as the immune system has both tumor-promoting and -inhibiting roles. In non-small cell lung cancer (NSCLC), there is a marked infiltration of different types of immune cells, and the distribution, tissue localization, and cell types are significantly associated with progression and survival. Cancer immunotherapy has seen a significant progress during the last decade. An increased understanding of the mechanisms by which lung cancer cells escape the immune system, and the recognition of the key tumor antigens and immune system components in tumor ignorance have led to the development of several lung cancer vaccines. As the NSCLC prognosis in general is dismal, one may hope that future immunotherapy may be an effective adjunct to standard therapy, reversing immunologic tolerance in the tumor microenvironment. This review reports on the tumor stroma and in particular tumor-suppressing and -promoting roles of the immune system. Furthermore, it presents recent literature on relevant immune cell-related research in NSCLC.

Immunoscore is a prognostic tool defined to quantify in situ immune cell infiltrates and appears highly promising as a supplement to the tumor-node-metastasis (TNM) classification of various tumors. In colorectal cancer, an international task force has initiated prospective multicenter studies aiming to implement TNM-Immunoscore (TNM-I) in a routine clinical setting. In breast cancer, recommendations for the evaluation of tumor-infiltrating lymphocytes (TILs) have been proposed by an international working group. Regardless of promising results, there are potential obstacles related to implementing TNM-I into the clinic. Diverse methods may be needed for different malignancies and even within each cancer entity. Nevertheless, a uniform approach across malignancies would be advantageous. In nonsmall-cell lung cancer (NSCLC), there are several previous reports indicating an apparent prognostic importance of TILs, but studies on TILs in a TNM-I setting are sparse and no general recommendations are made. However, recently published data is promising, evoking a realistic hope of a clinical useful NSCLC TNM-I. This review will focus on the TNM-I potential in NSCLC and propose strategies for clinical implementation of a TNM-I in resected NSCLC.

Purpose: The vascular endothelial growth factors (VEGF-A, -C, -D) and the VEGF receptors (VEGFR-1, -2, and -3) are important molecular markers in angiogenesis and lymphangiogenesis. This study elucidates the prognostic significance of these molecular markers in tumor cells as well as in the tumor stroma of resected non–small cell lung cancer tumors. Experimental Design: Tumor tissue samples from 335 resected patients with stage I to IIIA disease were obtained and tissue microarrays were constructed from duplicate cores of tumor cells and surrounding stromal tissue from each resected specimen. Immunohistochemistry was used to evaluate the expression of each molecular marker. Microvessel density was assessed by CD34 immunohistochemical staining. Results: In univariate analyses, high tumor cell expression of VEGF-A (P = 0.0005), VEGFR-1 (P = 0.013), VEGFR-2 (P = 0.006), and VEGFR-3 (P = 0.0003) were negative prognostic indicators for disease-specific survival (DSS). In tumor stroma, however, high expression of VEGF-A (P = 0.017), VEGF-C (P = 0.003), VEGF-D (P = 0.009), VEGFR-1 (P = 0.01), and VEGFR-2 (P = 0.019) correlated with good prognosis. There was no significant correlation between microvessel density and DSS. In multivariate analyses, high expression in tumor cells of VEGFR-3 (P = 0.007) was an independent negative prognostic factor for DSS, whereas in stromal cells, high VEGF-C (P = 0.004) expression had an independent positive survival impact. Conclusion: These are the first tissue microarray data in non–small cell lung cancers showing a positive prognostic impact by highly expressed angiogenic markers in tumor stroma, with VEGF-C as a major independent prognostic indicator.

Vimentin, nuclear factor-kB (NF-kB) p105, fascin, E-cadherin, TGF-b, Par6 and atypical PKC are molecular markers that play an important role in cell differentiation. Herein, we investigate their prognostic impact in primary non-small-cell carcinoma (NSCLC). Tumour tissue samples from 335 resected patients with stage I -IIIA were used. Tissue microarrays were constructed from duplicate cores of both neoplastic cells and stromal cells and were immunohistochemically evaluated. In univariate analyses, high tumour epithelial cell expressions of NF-kB p105 (P ¼ 0.02) and E-cadherin (P ¼ 0.03) were positive prognostic indicators for disease-specific survival (DSS), whereas high tumour epithelial cell expression of vimentin (P ¼ 0.001) was a negative prognostic indicator. High expression of NF-kB p105 (P ¼ 0.001) and Par6 (P ¼ 0.0001) in the stromal compartment correlated with a good prognosis. In multivariate analyses, the tumour epithelial cell expression of NF-kB p105 (P ¼ 0.0001) and vimentin (P ¼ 0.005) and the stromal cell expression of NF-kB p105 (P ¼ 0.007) and Par6 (P ¼ 0.0001) were independent prognostic factors for DSS. High expression of NF-kB p105 and low expression of vimentin in tumour epithelial cells are independent predictors of better survival in primary NSCLC. In stromal cells, high expressions of NF-kB p105 and Par6 are both favourable independent prognostic indicators.

A high density of CD8+ lymphocytes, especially in tumor epithelial areas, is an independent negative prognostic factor for biochemical failure-free survival.