Blood immune cell biomarkers in lung cancer

Characterization of host immune cell parameters prior to treatment is expected to identify biomarkers predictive of clinical outcome as well as to elucidate why some patients fail to respond to immunotherapy. We monitored blood immune cells from 58 patients with non-small- cell lung cancer (NSCLC) undergoing surgery of the primary tumor and from 50 age-matched healthy volunteers. Complete leukocyte blood count, the number of circulating dendritic cells (DC), HLA-DR^low monocytes and several lymphocytic subpopulations were determined by eight-color flow cytometry. Furthermore, the prognostic value of the immune cell parameters investigated was evaluated by patients’ survival analysis. Compared to the control group, blood of NSCLC patients contained more neutrophils resulting in a higher neutrophil-to-lymphocyte ratio (NLR), but a lower number of blood DC, in particular of plasmacytoid DC (pDC), natural killer (NK) cells and naive CD4⁺ and CD8⁺ T cells. Furthermore, a higher frequency of CD4⁺ regulatory T cells (Treg) and HLA-DR^low monocytes was detected, and smoking had a significant impact on these values. HLA-DR^low monocytes were positively correlated to the number of neutrophils, monocytes and NLR, but negatively associated with the number of pDC and naive CD4⁺ T cells. The frequency of Treg, HLA-DR^low monocytes and naive CD4⁺ and CD8⁺ T cells as well as the ratios of CD4/HLA-DR^low monocytes and HLA-DR^low monocytes/pDC correlated with patient’s overall survival. Next to Treg, HLA-DR^low monocytes and naive T cells represent prognostic markers for NSCLC patients and might be useful for monitoring of patients’ responses to immunotherapies in future studies.     

Resistance to Apoptosis and Expansion of Regulatory T Cells in Relation to the Detection of Circulating Tumor Cells in Patients with Metastatic Epithelial Cancer

Regulatory T cells may be crucial in the development of T cell tolerance to malignancies and contribute to immune dysfunctions. We investigated the percentage, activity, and onset of apoptosis of T cell subpopulations by multicolor flow cytometry in metastatic epithelial cancer patients compared to normal controls. Furthermore, a possible relationship between the presence of circulating tumor cells detected by immunocytochemistry and immune cell abnormalities was evaluated. Our study demonstrated a significantly elevated proportion of regulatory T cells in cancer patients (p < 0.001). In contrast to all other T cell subpopulations, regulatory T cells showed comparable Annexin V-binding characteristics in patients and normal controls. No relationship between the detection of circulating tumor cells and immune dysfunction was observed. These results indicate that cancer patients have a higher number of regulatory T cells with resistance to apoptotic stimuli partly responsible for immune dysfunctions as often observed in cancer patients.     

Different morphology,stage and treatment affect immune cell infiltration and long‐term outcome in patients with non‐small‐cell lung carcinoma

da Costa Souza P, Parra E R, Atanazio M J, da Silva O B, Noleto G S, Ab’Saber A M, de Morais Fernezlian S, Takagaki T & Capelozzi V L
(2012) Histopathology  61, 587–596 Different morphology, stage and treatment affect immune cell infiltration and long‐term outcome in patients with non‐small‐cell lung carcinoma Aims: Development of effective immune‐based therapies for patients with non‐small‐cell lung carcinoma (NSCLC) depends on an accurate characterization of complex interactions that occur between immune cells and the tumour environment. Methods and results: Innate and adaptive immune responses were evaluated in relation to prognosis in 65 patients with surgically excised NSCLC. Immunohistochemistry and morphometry were used to determine the abundance and distribution of immune cells. We found low numbers of immune cells and levels of cytokines in the tumour environment when compared with surrounding parenchyma. Smoking was associated inversely with the adaptive immune response and directly with innate immunity. We observed a prominent adaptive immune response in squamous cell carcinomas (SCC) but greater innate immune responses in adenocarcinomas and large cell carcinomas. Cox model analysis showed a low risk of death for smoking <41 packs/year, N₀ tambour stage, squamous carcinoma, CD4⁺ > 16.81% and macrophages/monocytes >4.5%. Collectively, the data indicate that in NSCLC there is not a substantive local immune cell infiltrate within the tumour. Conclusion: Although immune cell infiltration is limited in NSCLC it appears to have an impact on prognosis and this may be of relevance for new immunotherapeutic approaches.     

CD4~+ CD25~+调节性T细胞及Foxp3基因在不同淋巴结转移状态的非小细胞肺癌患者中的表达差异

目的:比较CD4+CD25+调节性T细胞及Foxp3基因在不同淋巴结转移状态的非小细胞肺癌患者外周血及肿瘤微环境中的表达差异。方法:46例初诊、初治的非小细胞肺癌患者根据有无淋巴结转移分为两组,采用流式细胞仪检测两组患者外周血中CD4+CD25+调节性T细胞的比例,Real-time PCR检测Foxp3基因的表达,免疫组化法检测肿瘤微环境中Foxp3的表达情况,ELISA法检测外周血及肿瘤组织匀浆中的TGF-β和IFN-γ水平。结果:Foxp3基因在转移淋巴结中的表达明显强于无转移的淋巴结,有淋巴结转移的非小细胞肺癌患者肿瘤微环境中的Foxp3表达明显强于无淋巴结转移的非小细胞肺癌患者,前者肿瘤组织匀浆中的TGF-β水平也明显高于后者,差异均具有显著性。两组患者外周血中CD4+CD25+调节性T细胞比例、Foxp3基因的表达及TGF-β、IFN-γ水平比较无显著性差异。结论:有淋巴结转移的非小细胞肺癌患者肿瘤微环境中存在Foxp3基因表达增强及TGF-β水平增高的现象,提示该类患者存在较为严重的局部肿瘤免疫抑制状态。     

Merkel Cell Tumor of the Penis

Abstract

An unusual presentation of Merkel cell tumor located on the penis of a 67-year old black man is described. The tumor was initially diagnosed as metastatic undifferentiated carcinoma. Light microscopy, immunohistochemistry, and electron microscopy were used to arrive at the final diagnosis. (The J Histotechnol 17:361, 1994)     

Abstracts from Current Literature

Abstract

The diagnostic utility of immunohistochemistry in the often difficult diagnosis of metastatic breast carcinoma is illustrated in a case involving an unusual anatomic location, the orbital region. Immunohistochemical stains on suitably fixed tissue were able to demonstrate clearly metastatic carcinoma in what initially to be an infiltrate A panel of AEl/AE3, epithelial membrane antigen, and BRST-2 antibodies was used with a streptavidin-biotin method. This case suggests that orbital biopsies be processed in a manner similar to lymph node biopsies(The J Histotechnol 15:139, 1992)     

Discordance between anaplastic lymphoma kinase status in primary non‐small‐cell lung cancers and their corresponding metastases

Aims: The anaplastic lymphoma kinase gene (ALK) has attracted considerable attention as a potential molecular target in non‐small‐cell lung cancer (NSCLC). However, it is unclear whether ALK alterations are acquired during the metastatic progression of NSCLC. Methods and results: ALK status and ALK expression were evaluated in a series of 67 primary NSCLCs and their corresponding metastatic lesions using fluorescence in‐situ hybridization and immunohistochemistry. ALK rearrangement was detected in 7.5% (5/67) of the primary tumours and in 9.0% (6/67) of the metastases (P < 0.001). ALK copy number gain (CNG) was detected in 1.5% (1/67) of the primary tumours and in 35.8% (24/67) of the metastases. Whereas ALK rearrangement was detected only in adenocarcinomas, CNG was identified in various histological subtypes of NSCLC. ALK expression was detected in 11.9% (8/67) of the primary tumours and in 25.4% (17/67) of the metastatic lesions. Conclusions: ALK alteration and ALK expression can be acquired during metastatic progression in NSCLC, and ALK CNG is associated with ALK expression.     

The Expression and Clinical Signification of PD-1 in Lymph Nodes of Patients with Non-small Cell Lung Cancer

To screen anti-programmed cell death protein 1 (PD-1) antibody treatment of the dominant population, it is necessary to understand the expression of PD-1 in tumor metastasis microenvironment. The aim of the present study was to detect the expression of PD-1 in lymph nodes of 51 patients with non-small cell lung cancer (NSCLC) by using flow cytometry (FCM). The results showed that the PD-1 expression on CD3⁺ T cells was significantly increased in NSCLC metastatic lymph nodes (50.08 ± 8.03%) compared with nonmetastatic lymph nodes (36.25 ± 11.27%) (t = 5.208, p < 0.001).We also found that PD-1 expression was not associated with age, sex, and smoking, and it is associated with pathological type and staging of lung cancer. This study demonstrated that PD-1 may involve in lymph nodes metastasis and promote the understanding of the mechanism of immunotherapies in the NSCLC.     

TNF-alpha Production by Peripheral Blood Monocytes in Multiple Sclerosis Patients and Healthy Controls

Background: Aberrant immune responses are evident in the pathogenesis of multiple sclerosis (MS) and it has been proposed that the spectrum of cytokines influence disease outcomes. Leptin and lipopolysaccharide (LPS) of Gram-negative bacteria are both potent cellular stimulators for production of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α). The aim of this study was to compare the TNF-α production by peripheral blood monocytes from MS patients with healthy controls.

Methods: Peripheral blood samples were stimulated with LPS or leptin. After blocking the Golgi apparatus, intracellular cytokine production was assessed using a monoclonal antibody against human TNF-α by the flow cytometry technique. Moreover, plasma level measurement of cytokines was performed using enzyme-linked immunosorbent assay (ELISA).

Results: Intracellular levels of TNF-α were 16.80?±?8.21 and 16.52?±?8.23in MS patients and healthy controls which showed no statistically significant difference between them (p?=?0.850). Leptin-stimulated and LPS-stimulated TNF-α production showed no significant difference between MS patients and the control group (p?=?0.263 and p?=?0.191, respectively). However, after treatment with leptin, a weak significant difference was shown between cases and control group (p?=?0.049). There were significant differences between cases and controls regarding serum levels of IL-6 and Toll-like receptor-4 (TLR-4) before and after stimulation with leptin and LPS, separately (p?<?0.05).

Conclusion: Taken together, we cannot definitely conclude that TNF-α does not play an important role in pathogenesis of MS. However, other characteristics of monocyte activation such as IL-6 or TLRs can elucidate implication of peripheral blood monocytes in MS pathogenesis.     

Tripterygium wilfordii Hook F extract in cART-treated HIV patients with poor immune response: a pilot study to assess its immunomodulatory effects and safety

Background:

Despite combination antiretroviral therapy (cART), 20% of HIV-infected patients are unable to achieve adequate immunologic recovery, in which immune activation plays a crucial role. We hypothesize that extract of Tripterygium wilfordii Hook F (TwHF), a Chinese medication used to treat autoimmune diseases, has immunomodulatory effects that may help CD4 cell recovery.

Methods:

Eighteen cART-treated HIV-infected patients virally suppressed for over 12 months with suboptimal CD4 cell recovery were enrolled. TwHF extract was administered at a dosage of 10?mg three times daily for 12 months. T-cell subsets and activation markers were evaluated at baseline and during follow-up. The trial was registered at Clinicaltrials.gov (NCT02002286).

Results:

TwHF extract was associated with a mean increase in CD4 cell count of 88?cells/μl (95% confidential interval [CI], 72–105?cells/μl) after one year of treatment. A significant increase in the mean rate of CD4 cell recovery (26 before vs 75?cells/μl/year after TwHF use, P?Conclusion:

Use of TwHF extract in HIV-infected patients was associated with a reduction in T-cell activation and improved CD4 recovery with an excellent safety profile.     

miRNA‐214 is related to invasiveness of human non‐small cell lung cancer and directly regulates alpha protein kinase 2 expression

The prognosis of non‐small cell lung cancer (NSCLC) is poor, since it has often metastasized to distant organs by the time of diagnosis. Therefore, biomarkers predicting metastasis are crucial. miRNAs play important roles in the regulation of different tumor cell processes, including metastasis. We recently showed that miRNA‐214 is linked to a radioresistant phenotype of NSCLC. miRNA‐214 has been linked to metastasis in other tumor types. Therefore, we examined the role of miRNA‐214 in the metastatic potential of NSCLC. We showed that downregulation of miRNA‐214 increased invasive potential, and conversely, overexpression of miRNA‐214 decreased invasiveness of NSCLC cells in vitro. Gene expression and bioinformatic analyses of NSCLC cells with ablated miRNA‐214, identified a number of metastasis‐related target genes, including pregnancy‐associated plasma protein A (PAPP‐A), alpha protein kinase 2 (ALPK2), cyclin‐dependent kinase 6 (CDK6) and tumor necrosis‐factor alpha‐induced protein 3 (TNFAIP3). These were validated on mRNA and protein level to be regulated by miRNA‐214. Through immunoprecipitation we showed that only ALPK2 is directly regulated by miRNA‐214. We also examined the protein expression of these four genes in NSCLC tumors with respect to metastatic potential. These results showed that NSCLC tumors express these proteins at moderate‐high levels in the nucleus, cytoplasm and/or plasma membrane although with no significant correlation to the overall survival or the metastatic potential of the patients. However, we also showed that the membrane‐localized PAPP‐A had a higher expression level compared to the cytoplasm‐localized. In conclusion, we show that low miRNA‐214 expression is linked to a higher invasive potential of NSCLC cells. © 2013 Wiley Periodicals, Inc.     

FRAS1蛋白与非小细胞肺癌脑转移的关系

目的:探讨FRAS1蛋白与非小细胞肺癌(NSCLC)脑转移的关系。方法:采用q PCR检测FRAS1的mRNA在NSCLC脑转移组织和同期原发灶组织中的表达水平,采用SP免疫组化法检测FRAS1蛋白在肺癌组织和癌旁非肿瘤组织的表达水平,以及有脑转移和无脑转移NSCLC原发灶组织中FRAS1蛋白的表达水平。结果:FRAS1 mRNA在肺癌脑转移灶中的表达量是肺癌原发灶中的近10倍,差异具有统计学显著性(P0.05);FRAS1蛋白在肺癌组织内表达,但在癌旁非肿瘤组织内未见表达;FRAS1蛋白在有脑转移NSCLC患者的肺癌组织中表达明显高于无脑转移NSCLC患者的肺癌组织,差异具有统计学显著性(P0.01)。结论:NSCLC组织中FRAS1蛋白表达可能与肺癌发生有关,同时肺癌组织中FRAS1蛋白高表达可能与肺癌脑转移密切相关。     

Optimized algorithm for Sanger sequencing-based <Emphasis Type="Italic">EGFR</Emphasis> mutation analyses in NSCLC biopsies

Pulmonary adenocarcinoma patients harboring EGFR mutations can benefit from tyrosine kinase inhibitor therapy. Reliable molecular analyses and precise pathological reporting of the EGFR mutational status are factors essential for patient treatment and outcome. More than 70 % of all EGFR mutation analyses are performed on non-small cell lung cancer (NSCLC) biopsies. However, biopsies may not be sufficient for mutation analysis due to low tumor content and admixture with non-neoplastic cells. To define the minimal concentration of tumor cells required for reliable EGFR mutational diagnostics by Sanger sequencing and to develop an algorithm for routine diagnostics on biopsy material, we determined total numbers of tumor and non-tumor cells, calculated the tumor cell concentration and serially diluted DNA from EGFR-mutated NSCLC by adding DNA of non-tumor cells from the same section. A counted tumor cell concentration of 30 %, which refers to a histologically estimated concentration of 40 %, is necessary for reliable detection of all mutations. Based on these data, we developed an algorithm for evidence-based EGFR mutation analysis by Sanger sequencing in biopsy specimens, which was subsequently applied to 461 diagnostic cases. Optimized diagnostic testing results in 80 % reliable EGFR mutation analyses of biopsy specimens, while in 20 % of cases re-biopsies had to be recommended.     

p21活化激酶4在非小细胞肺癌中的表达及其临床意义

目的:探讨p21活化激酶4(PAK4)在人非小细胞肺癌细胞系及人非小细胞肺癌组织中的表达及其临床意义。方法:采用Western blot及实时荧光定量PCR检测人支气管上皮(HBE)细胞、非小细胞肺癌细胞(A549、NCI-H520、NCI-H460和NCI-H596细胞)、20例新鲜非小细胞肺癌组织及相应的癌旁组织中PAK4的表达情况;采用免疫组化检测210例非小细胞肺癌组织PAK4的表达情况;采用Kaplan-Meier法评估非小细胞肺癌患者术后5年生存率;用Cox比例风险模型分析PAK4对患者预后的影响。结果:非小细胞肺癌细胞(A549、NCI-H520、NCI-H460和NCI-H596细胞)PAK4蛋白及mRNA表达均显著高于HBE细胞(P0.05);20例非小细胞肺癌组织中PAK4蛋白及mRNA表达高于癌旁组织PAK4蛋白及mRNA表达(P0.05);10例转移性非小细胞肺癌组织PAK4 mRNA表达显著高于10例原发性非小细胞肺癌组织(P0.05);免疫组化染色结果示210例非小细胞肺癌PAK4评分显著高于对应的癌旁组织。临床资料分析显示PAK4蛋白表达与非小细胞肺癌的分化程度、淋巴结转移、远处转移及临床分期有关(P0.05);PAK4高表达组患者5年生存率显著低于PAK4蛋白低表达组患者(logrank检验,P0.05),PAK4蛋白表达是非小细胞肺癌患者的独立预后因素。结论:PAK4蛋白高表达是非小细胞肺癌患者死亡的独立危险因素。     

Cellular immune responses in amniotic fluid of women with preterm clinical chorioamnionitis

Objective

Preterm birth is the leading cause of neonatal morbidity and mortality worldwide. Some preterm births are associated with clinical chorioamnionitis; yet, this condition has been poorly investigated. Herein, we characterized the amniotic fluid cellular immune responses in women with preterm clinical chorioamnionitis.

Methods and subjects

Amniotic fluid samples were obtained from women with preterm clinical chorioamnionitis and a positive or negative microbiological culture (n?=?17). The cellular composition of amniotic fluid was evaluated using fluorescence microscopy, scanning and transmission electron microscopy, and flow cytometry. Women without preterm clinical chorioamnionitis were also examined (n?=?10).

Results

Amniotic fluid from women with preterm clinical chorioamnionitis and a positive culture had: (1) abundant neutrophils associated with viable and non-viable bacteria, (2) neutrophils performing phagocytosis, (3) neutrophils forming NETs, (4) increased numbers of neutrophils, monocytes/macrophages, and CD4+?T cells, and (5) high expression of IL-1β by neutrophils and monocytes/macrophages. Amniotic fluid from women with preterm clinical chorioamnionitis and proven infection tended to have fewer monocytes/macrophages and CD4+?T cells compared to those without chorioamnionitis.

Conclusion

We provide the first morphologic and phenotypic characterization of the cellular immune responses in the amniotic cavity of women with preterm clinical chorioamnionitis, a condition associated with adverse neonatal outcomes.

     

Multispectral imaging for quantitative and compartment‐specific immune infiltrates reveals distinct immune profiles that classify lung cancer patients

Semiquantitative assessment of immune markers by immunohistochemistry (IHC) has significant limitations for describing the diversity of the immune response in cancer. Therefore, we evaluated a fluorescence‐based multiplexed immunohistochemical method in combination with a multispectral imaging system to quantify immune infiltrates in situ in the environment of non‐small‐cell lung cancer (NSCLC). A tissue microarray including 57 NSCLC cases was stained with antibodies against CD8, CD20, CD4, FOXP3, CD45RO, and pan‐cytokeratin, and immune cells were quantified in epithelial and stromal compartments. The results were compared with those of conventional IHC, and related to corresponding RNA‐sequencing (RNAseq) expression values. We found a strong correlation between the visual and digital quantification of lymphocytes for CD45RO (correlation coefficient: r = 0.52), FOXP3 (r = 0.87), CD4 (r = 0.79), CD20 (r = 0.81) and CD8 (r = 0.90) cells. The correlation with RNAseq data for digital quantification (0.35–0.65) was comparable to or better than that for visual quantification (0.38–0.58). Combination of the signals of the five immune markers enabled further subpopulations of lymphocytes to be identified and localized. The specific pattern of immune cell infiltration based either on the spatial distribution (distance between regulatory CD8⁺ T and cancer cells) or the relationships of lymphocyte subclasses with each other (e.g. cytotoxic/regulatory cell ratio) were associated with patient prognosis. In conclusion, the fluorescence multiplexed immunohistochemical method, based on only one tissue section, provided reliable quantification and localization of immune cells in cancer tissue. The application of this technique to clinical biopsies can provide a basic characterization of immune infiltrates to guide clinical decisions in the era of immunotherapy. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Interleukin-2 therapy of lymphoma-bearing immunosuppressed mice

In the present study, the immune status of syngeneic Balb/c animals bearing a poorly metastatic RAW117-P lymphoma and the highly malignant liver metastatic variant RAW117-H10 lymphoma were measured and compared to control animals with no known tumor. The immune status was evaluated by performing various analyses of spleen cells for the frequencies of immune cells using flow cytometry,in vitro mitogen response andin vitro NK cell-mediated cytotoxicity assays on days 6, 9 and 12 after tumor transplantation. The results of these studies indicated that from day 9 onwards, some of the immune response of the RAW117 lymphoma-bearing animals appeared to decrease compared to control animals. In order to boost the immune response of the tumor-bearing immunosuppressed animals, recombinant interleukin-2 (rIL-2) was administered to RAW117-H10 lymphoma-bearing animals. The immune status of tumor-bearing animals treated with rIL-2 was evaluated on days 5, 10 and 15 after tumor transplantation using similar analyses of spleen cells as described above. The results of these experiments indicated that IL-2 treatment increased splenic levels of cytotoxic cells, and decreased thein vivo tumorigenicity/metastasis of metastatic RAW117-H10 lymphoma cells. rIL-2 administration resulted in a significant increase in survival of tumor-bearing animals, and histological studies showed significantly lower tumor burdens in treated animals: it appears that rIL-2 has a beneficial therapeutic effect on immunosuppressive metastatic RAW117 lymphoma.     

Composition of the immune microenvironment differs between carcinomas metastatic to the lungs and primary lung carcinomas

Lungs are among the most common sites for development of both primary and metastatic carcinomas. Tumor cells expression (TC) of PD-L1 is an important predictor of the of response to immune check-point inhibition in NSCLC, while the composition of the immune cells (IC) in the tumor microenvironment including PD-L1 + cells is believed to predict responses in tumors of some other primary sites. Total mutational load (TML) and microsatellite instability (MSI) also play a role in response to the immune checkpoint blockade. We investigated immune microenvironment characteristics (PD-1, PD-L1, CD8) of 257 lung biopsies including 81 primary (NSCLC) and 176 metastatic tumors to the lungs. TML and MSI were calculated from massively parallel sequencing (592-gene panel). TC expression of PD-L1 was more common in NSCLC than in metastatic carcinomas (28% vs. 10%, p = 0.009), while PD-L1-positive IC were present at relevant percentages (1–5%) exclusively in metastatic carcinomas (31% IC positive vs. 0%, p < 0.001). Metastatic carcinomas carried significantly lower TML in comparison with the NSCLCs (6.6 mutations on average vs. 10, p = 0.01). All primary NSCLC were microsatellite stable, and only 2 metastatic carcinomas exhibited MSI-H status. The number of PD-1 + and CD8 + tumor infiltrating lymphocytes did not differ significantly between the primary and metastatic carcinomas. Our study revealed significant differences in tumor immune microenvironment (PD-L1 in IC and TC), and its relationship to TML between NSCLC and metastatic cancers. These differences could determine the choice of a predictive biomarker test and subsequently effect(s) of the immune therapy treatments in various advanced cancers.     

Microsatellite instability in primary and metastatic lung carcinomas

Fifty-seven primary lung carcinomas and 35 metastatic lung carcinomas were analyzed for microsatellite instability at 11 different chromosomal loci. Although no instability was detected in 37 small cell lung carcinomas (SCLC), it was frequently detected in non-small cell lung carcinomas (NSCLC) (16/55, 29%). In NSCLC, the incidence of replication errors (RERs) in metastatic tumors (12/22, 55%) was significantly higher than that in primary tumors (4/33, 12%) (P = 0.0021). Among 10 pairs of primary tumors and corresponding metastases, there were 4 cases which manifested the identical RER phenotypes in both primary and metastatic tumors. In two cases, RER phenotypes were detected in metastatic but not in primary tumors. Never was an RER phenotype found only in a primary tumor but not in the metastases. RERs were detected more frequently in stage III or IV tumors (3/8, 38%) than stage I or II tumors (1/25, 4%) (P = 0.0359). Tumor cells with allelic losses on chromosome arm 3p or 18q tended to have RER phenotypes (P = 0.0432 and P = 0.0187, respectively). The data suggest that microsatellite instability is common in NSCLC but not in SCLC, and that genomic instability appears late in tumor progression and plays an important role in the acquisition of more malignant phenotypes in NSCLC.