Establishment of an immortalized cell line from a precancerous lesion of lung adenocarcinoma, and genes highly expressed in the early stages of lung adenocarcinoma development

Aberrant OCIAD2 demethylation in lung adenocarcinoma is associated with outcome

Overexpression of OCIAD2 in lung adenocarcinoma has already been reported in several research articles, but the molecular mechanism involved remains unknown. Promoter CpG methylation is a representative form of epigenetic gene regulation, and a considerable number of tumor suppressor genes show hypermethylation in many cancers. In contrast, promoter CpG hypomethylation causes oncogene overexpression, resulting in carcinogenesis and malignant progression. In the present study, we investigated the CpG methylation and expression status of OCIAD2 using tumor tissues and adjacent normal tissues from seven cases of lung adenocarcinoma. We also examined the relationship between CpG methylation status and outcome in 58 patients with adenocarcinoma. Pyrosequencing showed that CpG sites in OCIAD2 promoter regions were more frequently demethylated in tumor tissues than in adjacent normal tissues, and reverse transcription-quantitative polymerase chain reaction revealed overexpression of OCIAD2 in lung adenocarcinoma. There was a correlation between OCIAD2 CpG demethylation and the level of mRNA expression, and statistical analysis showed that CpG hypomethylation of OCIAD2 was associated with poor outcomes. Our results suggest that overexpression of OCIAD2 might be caused mainly by CpG hypomethylation and that OCIAD2 methylation status might be a useful prognostic indicator in lung adenocarcinoma.

Ovarian carcinoma immunoreactive antigen domain 2 controls mitochondrial apoptosis in lung adenocarcinoma

Ovarian carcinoma immunoreactive antigen domain 2 (OCIAD2) has been reported to show significantly higher expression in invasive lung adenocarcinoma than in lung adenocarcinoma in situ, and its abnormal expression is associated with poorer prognosis of the patients. However, the cellular function of OCIAD2 in this tumor remains poorly understood. In the present study, we first validated that OCIAD2 showed higher expression in human lung adenocarcinoma tissues or cell lines than in normal lung tissue or immortalized normal bronchial epithelial cells. OCIAD2 was localized predominantly at the mitochondrial membrane in lung adenocarcinoma cells. Interestingly, suppression of OCIAD2 led to loss of mitochondrial structure and a reduction in the number of mitochondria. Moreover, OCIAD2 suppression led to downregulation of cellular growth, proliferation, migration, and invasion, and upregulation of mitochondria‐related apoptosis. We also showed that OCIAD2 suppression induced a decrease in mitochondrial membrane potential and release of cytochrome c. Transcriptional profiling using RNA sequencing revealed a total of 137 genes whose expression was commonly altered after OCIAD2 knockdown in three lung adenocarcinoma cell lines (A549, HCC827, and PC9). Pathway enrichment analysis of those genes demonstrated significant enrichment in apoptotic signaling or endoplasmic reticulum (ER) stress pathways. Our data suggest that OCIAD2 inhibits the mitochondria‐initiated apoptosis and thus promotes the survival of lung cancer cells. Therefore, OCIAD2 may be an effective target for treatment of lung adenocarcinoma.

Cellular models of development of ovarian high-grade serous carcinoma: A review of cell of origin and mechanisms of carcinogenesis

High-grade serous carcinoma (HGSC) is the most common and malignant histological type of epithelial ovarian cancer, the origin of which remains controversial. Currently, the secretory epithelial cells of the fallopian tube are regarded as the main origin and the ovarian surface epithelial cells as a minor origin. In tubal epithelium, these cells acquire TP53 mutations and expand to a morphologically normal 'p53 signature' lesion, transform to serous tubal intraepithelial carcinoma and metastasize to the ovaries and peritoneum where they develop into HGSC. This shifting paradigm of the main cell of origin has revolutionarily changed the focus of HGSC research. Various cell lines have been derived from the two cellular origins by acquiring immortalization via overexpression of hTERT plus disruption of TP53 and the CDK4/RB pathway. Malignant transformation was achieved by adding canonical driver mutations (such as gain of CCNE1) revealed by The Cancer Genome Atlas or by noncanonical gain of YAP and miR181a. Alternatively, because of the extreme chromosomal instability, spontaneous transformation can be achieved by long passage of murine immortalized cells, whereas in humans, it requires ovulatory follicular fluid, containing regenerating growth factors to facilitate spontaneous transformation. These artificially and spontaneously transformed cell systems in both humans and mice have been widely used to discover carcinogens, oncogenic pathways and malignant behaviours in the development of HGSC. Here, we review the origin, aetiology and carcinogenic mechanism of HGSC and comprehensively summarize the cell models used to study this fatal cancer having multiple cells of origin and overt genomic instability.

Mechanomics Biomarker for Cancer Cells Unidentifiable through Morphology and Elastic Modulus

Cellular mechanical properties are potential cancer biomarkers used for objective cytology to replace the current subjective method relying on cytomorphology. However, heterogeneity among intra/intercellular mechanics and the interplay between cytoskeletal prestress and elastic modulus obscured the difference detectable between malignant and benign cells. In this work, we collected high density nanoscale prestress and elastic modulus data from a single cell by AFM indentation to generate a cellular mechanome. Such high dimensional mechanome data was used to train a malignancy classifier through machine learning. The classifier was tested on 340 single cells of various origins, malignancy, and degrees of similarity in morphology and elastic modulus. The classifier showed instrument-independent robustness and classification accuracy of 89% with an AUC-ROC value of 93%. A signal-to-noise ratio 8 times that of the human-cytologist-based morphological method was also demonstrated, in differentiating precancerous hyperplasia cells from normal cells derived from the same lung cancer patient.

Cytoplasmic expression of epithelial cell transforming sequence 2 in lung adenocarcinoma and its implications for malignant progression

Epithelial cell transforming sequence 2 (ECT2), a guanine nucleotide exchange factor, is predominantly localized in the nucleus of non-transformed cells and functions to regulate cytokinesis. ECT2 is also localized in the cytoplasm of cancer cells. Aberrant cytoplasmic expression of ECT2 is thought to drive tumor growth and invasion. In this study, we investigated the cytoplasmic expression of ECT2 and its prognostic and biological significance in lung adenocarcinoma. Western blotting of cellular fractions from the nucleus and cytoplasm was performed to determine the subcellular localization of ECT2 in lung adenocarcinoma cell lines. The cytoplasmic expression of ECT2 in 167 lung adenocarcinomas was evaluated by immunohistochemistry and its clinical significance was examined using Kaplan-Meier curves and Cox regression analysis. Scraping cytology specimens of 13 fresh lung adenocarcinomas were used to assess the subcellular localization of ECT2 and its phosphorylation at Thr790 (P-ECT2(T790)). We found that ECT2 was localized in both the nucleus and cytoplasm of lung adenocarcinoma cell lines and tumor tissues. Cytoplasmic expression of ECT2 was detected by immunohistochemistry in 83 (50%) of the lung adenocarcinomas, and was found to increase during cancer progression. It was expressed in 30 (29%) small adenocarcinomas ( ≤ 2 cm in diameter) and 53 (82%) advanced adenocarcinomas ( > 2 cm in diameter). Cytoplasmic positivity for ECT2 was associated with a poor outcome in terms of both disease-free and overall survival (both P < 0.001), and was an independent prognostic factor for overall survival (P = 0.025). Immunocytochemical staining for P-ECT2(T790) demonstrated cytoplasmic and membrane positivity in Calu-3 cells and scraping cytology specimens. Positive P-ECT2(T790) staining was correlated with cytoplasmic ECT2 expression in 6 of 13 scraped cytology specimens tested. In conclusion, our findings indicate that cytoplasmic ECT2 expression could promote the malignant progression of lung adenocarcinoma and may represent a potent therapeutic target for patients with lung adenocarcinoma.

Influenza A Virus Infection Triggers Pyroptosis and Apoptosis of Respiratory Epithelial Cells through the Type I Interferon Signaling Pathway in a Mutually Exclusive Manner

Respiratory epithelial cell death by influenza virus infection is responsible for the induction of inflammatory responses, but the exact cell death mechanism is not understood. Here we showed that influenza virus infection induces apoptosis and pyroptosis in normal or precancerous human bronchial epithelial cells. Apoptosis was induced only in malignant tumor cells infected with influenza virus. In human precancerous respiratory epithelial cells (PL16T), the number of apoptotic cells increased at early phases of infection, but pyroptotic cells were observed at late phases of infection. These findings suggest that apoptosis is induced at early phases of infection but the cell death pathway is shifted to pyroptosis at late phases of infection. We also found that the type I interferon (IFN)-mediated JAK-STAT signaling pathway promotes the switch from apoptosis to pyroptosis by inhibiting apoptosis possibly through the induced expression of the Bcl-xL anti-apoptotic gene. Further, the inhibition of JAK-STAT signaling repressed pyroptosis but enhanced apoptosis in infected PL16T cells. Collectively, we propose that type I IFN signaling pathway triggers pyroptosis but not apoptosis in the respiratory epithelial cells in a mutually exclusive manner to initiate proinflammatory responses against influenza virus infection.IMPORTANCE Respiratory epithelium functions as a sensor of infectious agents to initiate inflammatory responses along with cell death. However, the exact cell death mechanism responsible for inflammatory responses by influenza virus infection is still unclear. We showed that influenza virus infection induced apoptosis and pyroptosis in normal or precancerous human bronchial epithelial cells. Apoptosis was induced at early phases of infection, but the cell death pathway was shifted to pyroptosis at late phases of infection under the regulation of type I IFN signaling to promote proinflammatory cytokine production. Taken together, our results indicate that the type I IFN signaling pathway plays an important role to induce pyroptosis but represses apoptosis in the respiratory epithelial cells to initiate proinflammatory responses against influenza virus infection.

Stratifin regulates stabilization of receptor tyrosine kinases via interaction with ubiquitin-specific protease 8 in lung adenocarcinoma

Previously we have reported that stratifin (SFN, 14-3-3 sigma) acts as a novel oncogene, accelerating the tumor initiation and progression of lung adenocarcinoma. Here, pull-down assay and LC-MS/MS analysis revealed that ubiquitin-specific protease 8 (USP8) specifically bound to SFN in lung adenocarcinoma cells. Both USP8 and SFN showed higher expression in human lung adenocarcinoma than in normal lung tissue, and USP8 expression was significantly correlated with SFN expression. Expression of SFN, but not of USP8, was associated with histological subtype, pathological stage, and poor prognosis. USP8 stabilizes receptor tyrosine kinases (RTKs) such as EGFR and MET by deubiquitination, contributing to the proliferative activity of many human cancers including non-small cell lung cancer. In vitro, USP8 binds to SFN and they co-localize at the early endosomes in lung adenocarcinoma cells. Moreover, USP8 or SFN knockdown leads to downregulation of tumor cellular proliferation and upregulation of apoptosis, p-EGFR or p-MET, which are related to the degradation pathway, and accumulation of ubiquitinated RTKs, leading to lysosomal degradation. Additionally, mutant USP8, which is unable to bind to SFN, reduces the expression of RTKs and p-STAT3. We also found that interaction with SFN is critical for USP8 to exert its autodeubiquitination function and avoid dephosphorylation by PP1. Our findings demonstrate that SFN enhances RTK stabilization through abnormal USP8 regulation in lung adenocarcinoma, suggesting that SFN could be a more suitable therapeutic target for lung adenocarcinoma than USP8.

A review of S100 protein family in lung cancer

S100 protein family, representing 25 relatively small calcium binding proteins, has been reported to be involved in multiple stages of tumorigenesis and progression. These proteins are considered having potential value to be adopted as novel biomarkers in the detection and accurate prediction of many kinds of tumors, including lung cancer. As the one having the highest morbidity and mortality among all cancers, lung carcinoma is still occult for detection, especially at early stage. S100 proteins take participation in the lung neoplasia through playing intracellular and/or extracellular functions, therefore getting involved in a variety of biological processes such as differentiation, proliferation, and migration. A few members have also been testified to modulate TGF-β/Smad-3 mediated transcriptional activity of target genes involved in tumor promotion. In addition to that, a number of proteins in this family have already been reported to experience an abnormal trend in lung cancer at cell, serum and tissue levels. Thus, S100 proteins may serve as effective biomarkers for suspected or already diagnosed lung cancer patients. In future, S100 protein family might be applied as therapeutic targets in clinical treatment of lung cancer. In this review, we firstly summed up the biological and clinical evidence connecting S100 proteins and lung cancer, which has not been summarized before.

Cyclophilin A expression and its prognostic significance in lung adenocarcinoma

Cyclophilin A (CypA) has been reported to be upregulated in malignant tumors. CypA expression is thought to be associated with acquisition of tumor growth and anti-apoptotic function. Although upregulation of CypA has been reported in lung adenocarcinoma, its clinicopathological significance and roles in malignant progression remain unclear. Here we investigated the implications of CypA expression for outcome in patients with lung adenocarcinoma. Lung adenocarcinoma specimens from 198 cases were selected and reclassified according to the World Health Organization classification (4th edition) and the Noguchi classification. CypA expression was assessed by immunohistochemistry, and the H-score was calculated on the basis of intensity and proportion. The specificity of the antibody used was confirmed by Western blotting and the cut-off point was determined from the ROC curve. Sixty-seven cases (33.8%) had low CypA expression (CypA-L group) and 131 (66.2%) had high CypA expression (CypA-H group). Many cases of adenocarcinoma in situ were CypA-L, and advanced adenocarcinomas tended to be classified as CypA-H. Clinically, patients with CypA-H tumors showed a significantly poorer prognosis than those with CypA-L tumors. This is the first investigation of the implications of the CypA expression level in terms of the clinical characteristics of resected lung adenocarcinomas.

miR-3941: A novel microRNA that controls IGBP1 expression and is associated with malignant progression of lung adenocarcinoma

Immunoglobulin (CD79a) binding protein 1 (IGBP1) is universally overexpressed in lung adenocarcinoma and exerts an anti‐apoptotic effect by binding to PP2Ac. However, the molecular mechanism of IGBP1 overexpression is still unclear. In the present study, we used a microRNA (miRNA) array and TargetScan Human software to detect IGBP1‐related miRNAs that regulate IGBP1 expression. The miRNA array analysis revealed more than 100 miRNAs that are dysregulated in early invasive adenocarcinoma. On the other hand, in silico analysis using TargetScan Human revealed 79 miRNAs that are associated with IGBP1 protein expression. Among the miRNAs selected by miRNA array analysis, six (miR‐34b, miR‐138, miR‐374a, miR‐374b, miR‐1909, miR‐3941) were also included among those selected by TargetScan analysis. Real‐time reverse transcription PCR (real‐time RT‐PCR) showed that the six microRNAs were downregulated in invasive adenocarcinoma (IGBP1+) relative to adjacent normal lung tissue (IGBP1−). Among these microRNAs, only miR‐34b and miR‐3941 depressed luciferase activity by targeting 3′UTR‐IGBP1 in the luciferase vector. We transfected miR‐34b and miR‐3941 into lung adenocarcinoma cell lines (A549, PC‐9), and both of them suppressed IGBP1 expression and cell proliferation. Moreover, the transfected miR‐34b and miR‐3941 induced apoptosis of a lung adenocarcinoma cell line, similarly to the effect of siIGBP1 RNA. As well as miR‐34b, we found that miR‐3941 targeted IGBP1 specifically and was able to exclusively downregulate IGBP1 expression. These findings indicate that suppression of miR‐3941 has an important role in the progression of lung adenocarcinoma at an early stage.

DNMT3a expression pattern and its prognostic value in lung adenocarcinoma

OBJECTIVES

DNA methyltransferases (DNMTs) are an important part of the methylation pathway that is highly correlated with the pathophysiology of cancers. Several studies have reported overexpression of DNMTs in human lung cancer, but none have compared the expression pattern to pathological features. In this study, we clarified the association of DNMT3a expression pattern with pathological features and prognosis of lung adenocarcinoma.

MATERIALS AND METHODS

135 cases of surgically resected lung adenocarcinoma specimens were used for DNMT3a immunohistochemistry (IHC). IHC score was determined by counting the number of positive nuclei. The ROC curve was drawn to determine the best cut-off point of the score; this was set at 57.5. Western blot also implemented and confirmed the specificity of the antibody. Correlations between expression pattern and clinicopathological features and prognosis were analyzed using chi-squared method and Cox proportional hazards model respectively.

RESULT

Seventy-nine of the 135 cases (58.5%) showed strong positive reactivity to anti-DNMT3a. In terms of histological subtypes, among invasive lung adenocarcinomas 41 out of 53 lepidic adenocarcinomas (77%) were strongly positive, while among the other histological subtypes only 23 out of 66 cases (34.8%) showed a positive reaction. Among non-invasive lung adenocarcinomas 15 out of 16 cases (93.8%) were strongly positive. The level of DNMT3a expression was associated with patient outcome, and patients with weak expression of DNMT3a had a poorer outcome than those with strong expression. Multivariate analysis also indicated that DNMT3a is an independent prognostic marker in lung adenocarcinoma.

CONCLUSION

Our results indicate that DNMT3a expression in lung adenocarcinoma is associated with the histologically non-invasive type and lepidic subtype, and a favorable prognosis. We also showed that DNMT3a expression is an independent prognostic marker in lung adenocarcinoma. Since lack of DNMT3a is thought to facilitate tumor progression, DNMT3a might be clinically applicable as an indicator of favorable prognosis.

Trop2 regulates motility and lamellipodia formation in cultured fetal lung fibroblasts

Proliferation and migration of fibroblasts are vital for fetal lung development. However, the regulatory mechanisms are poorly understood. We have previously shown that TROP2 gene expression is closely associated with fetal lung cell proliferation in vivo and that TROP2 knockdown decreases proliferation of fetal lung fibroblasts in culture. We hypothesized that the Trop2 protein also regulates the morphology and motility of fetal lung fibroblasts. Fibroblasts isolated from fetal rat lungs (gestational age embryonic day 19) adopted a myofibroblast-like morphology in culture. Trop2 protein was localized to lamellipodia. TROP2 siRNA significantly decreased: TROP2 mRNA levels by 77%, the proportion of cells containing Trop2 protein by 70%, and cell proliferation by 50%. TROP2 siRNA also decreased the degree of motility as determined by the number of gridlines that cells moved across (2.2 ± 0.2 vs. 3.2 ± 0.2; P < 0.001). TROP2 knockdown altered cell morphology, causing a notable absence of lamellipodia and abnormal localization of components of the cell migration apparatus, and it reduced phosphorylated ERK1 and ERK2 levels. In contrast, TROP2 overexpression significantly increased: TROP2 mRNA levels by 40-fold, cell proliferation by 40%, the proportion of cells that were motile by 20%, and the number of gridlines that cells moved across (2.1 ± 0.2 vs. 1.6 ± 0.1; P < 0.001). Our data suggest that Trop2 regulates cell proliferation and motility and that it does so by regulating the ERK pathway and several critical components of the cell migration apparatus.

S100A2 promoter-driven conditionally replicative adenovirus targets non-small-cell lung carcinoma

S100A2, a member of the S100 family of calcium-binding proteins, has been implicated in carcinogenesis as both a tumor suppressor and stimulator. Here, we characterized promoter activity of S100A2, generated an S100A2 promoter-driven conditionally replicative adenovirus (Ad/SA), and evaluated its anti-tumor activity in vitro and in vivo. Promoter activity of S100A2 was greatly restricted to tumor cells, and the S100A2 promoter bound with typical nuclear targets of epidermal growth factor receptor (EGFR) signaling. EGF-stimulated EGFR phosphorylation induced S100A2 expression and further activated E1A expression of Ad/SA, which was restored by EGFR signal inhibition in a concentration-dependent manner in non-small-cell lung carcinoma (NSCLC). In two EGFR-activated tumor xenograft animal models, Ad/SA exhibited potent anti-tumor activity, whereas cetuximab, an EGFR-targeting anticancer drug, was active transiently or ineffective. Combined treatment with cetuximab or cisplatin plus Ad/SA resulted in enhanced anti-tumor activity. Immunohistochemical analysis of tumor sections showed moderate-to-high grade signals for EGFR and adenovirus, and a reduction in viable cells in Ad/SA-treated tumors. Collectively, these results demonstrate that the S100A2 promoter-driven adenovirus is a potent inhibitor of cancers, and further suggest that S100A2 is a target gene of EGFR signaling pathway in NSCLC.

The oncogene Trop2 regulates fetal lung cell proliferation

The factors regulating growth of the developing lung are poorly understood, although the degree of fetal lung expansion is critical. The oncogene Trop2 (trophoblast antigen 2) is upregulated during accelerated fetal lung growth, and we hypothesized that it may regulate normal fetal lung growth. We investigated Trop2 expression in the fetal and neonatal sheep lung during accelerated and delayed lung growth induced by alterations in fetal lung expansion, as well as in response to glucocorticoids. Trop2 expression was measured using real-time PCR and localized spatially using in situ hybridization and immunofluorescence. During normal lung development, Trop2 expression was higher at 90 days gestational age (GA; 4.0 ± 0.8) than at 128 days GA (1.0 ± 0.1), decreased to 0.5 ± 0.1 at 142 days GA (full term ∼147 days GA), and was positively correlated to lung cell proliferation rates (r = 0.953, P < 0.005). Trop2 expression was regulated by fetal lung expansion, but not by glucocorticoids. It was increased nearly threefold by 36 h of increased fetal lung expansion (P < 0.05) and was reduced to ∼55% of control levels by reduced fetal lung expansion (P < 0.05). Trop2 expression was associated with lung cell proliferation during normal and altered lung growth, and the TROP2 protein colocalized with Ki-67-positive cells in the fetal lung. TROP2 was predominantly localized to fibroblasts and type II alveolar epithelial cells. Trop2 small interfering RNA decreased Trop2 expression by ∼75% in cultured fetal rat lung fibroblasts and decreased their proliferation by ∼50%. Cell viability was not affected. This study demonstrates that TROP2 regulates lung cell proliferation during development.

DNA methylation changes in atypical adenomatous hyperplasia, adenocarcinoma in situ, and lung adenocarcinoma

BACKGROUND

Aberrant DNA methylation is common in lung adenocarcinoma, but its timing in the phases of tumor development is largely unknown. Delineating when abnormal DNA methylation arises may provide insight into the natural history of lung adenocarcinoma and the role that DNA methylation alterations play in tumor formation.

METHODOLOGY/PRINCIPAL FINDINGS

We used MethyLight, a sensitive real-time PCR-based quantitative method, to analyze DNA methylation levels at 15 CpG islands that are frequently methylated in lung adenocarcinoma and that we had flagged as potential markers for non-invasive detection. We also used two repeat probes as indicators of global DNA hypomethylation. We examined DNA methylation in 249 tissue samples from 93 subjects, spanning the putative spectrum of peripheral lung adenocarcinoma development: histologically normal adjacent non-tumor lung, atypical adenomatous hyperplasia (AAH), adenocarcinoma in situ (AIS, formerly known as bronchioloalveolar carcinoma), and invasive lung adenocarcinoma. Comparison of DNA methylation levels between the lesion types suggests that DNA hypermethylation of distinct loci occurs at different time points during the development of lung adenocarcinoma. DNA methylation at CDKN2A ex2 and PTPRN2 is already significantly elevated in AAH, while CpG islands at 2C35, EYA4, HOXA1, HOXA11, NEUROD1, NEUROD2 and TMEFF2 are significantly hypermethylated in AIS. In contrast, hypermethylation at CDH13, CDX2, OPCML, RASSF1, SFRP1 and TWIST1 and global DNA hypomethylation appear to be present predominantly in invasive cancer.

CONCLUSIONS/SIGNIFICANCE

The gradual increase in DNA methylation seen for numerous loci in progressively more transformed lesions supports the model in which AAH and AIS are sequential stages in the development of lung adenocarcinoma. The demarcation of DNA methylation changes characteristic for AAH, AIS and adenocarcinoma begins to lay out a possible roadmap for aberrant DNA methylation events in tumor development. In addition, it identifies which DNA methylation changes might be used as molecular markers for the detection of preinvasive lesions.

High expression of stratifin is a universal abnormality during the course of malignant progression of early-stage lung adenocarcinoma

Adenocarcinoma in situ (AIS) of the lung has an extremely favorable prognosis, with a 5-year survival rate of 100%. However, early invasive adenocarcinoma (EIA) often has a fatal outcome. In this study, we compared the expression profiles of AIS with those of EIA showing lymph node metastasis or a fatal outcome, and screened the differentially expressed genes by cDNA microarray. From the genes selected, we focused on Stratifin (SFN, 14-3-3 σ), which showed significantly higher expression in EIA than in AIS. Immunohistochemistry for SFN revealed that more than 95% of EIAs were immunopositive for SFN, in comparison to only 13% of AISs (p <0.05). Interestingly, positivity was detected not only in the invasive region but also in the in situ spreading component of EIA. Functionally, SFN facilitates the cell proliferation capacity of lung adenocarcinoma. These results indicate that SFN overexpression is a universal abnormality during the stepwise progression from in situ to invasive adenocarcinoma of the lung.

Humanized anti-Trop-2 IgG-SN-38 conjugate for effective treatment of diverse epithelial cancers: preclinical studies in human cancer xenograft models and monkeys

PURPOSE

Evaluate the efficacy of an SN-38-anti-Trop-2 antibody-drug conjugate (ADC) against several human solid tumor types, and to assess its tolerability in mice and monkeys, the latter with tissue cross-reactivity to hRS7 similar to humans.

EXPERIMENTAL DESIGN

Two SN-38 derivatives, CL2-SN-38 and CL2A-SN-38, were conjugated to the anti-Trop-2-humanized antibody, hRS7. The immunoconjugates were characterized in vitro for stability, binding, and cytotoxicity. Efficacy was tested in five different human solid tumor-xenograft models that expressed Trop-2 antigen. Toxicity was assessed in mice and in Cynomolgus monkeys.

RESULTS

The hRS7 conjugates of the two SN-38 derivatives were equivalent in drug substitution (∼ 6), cell binding (K(d) ∼ 1.2 nmol/L), cytotoxicity (IC(50) ∼ 2.2 nmol/L), and serum stability in vitro (t/(½) ∼ 20 hours). Exposure of cells to the ADC demonstrated signaling pathways leading to PARP cleavage, but differences versus free SN-38 in p53 and p21 upregulation were noted. Significant antitumor effects were produced by hRS7-SN-38 at nontoxic doses in mice bearing Calu-3 (P ≤ 0.05), Capan-1 (P < 0.018), BxPC-3 (P < 0.005), and COLO 205 tumors (P < 0.033) when compared to nontargeting control ADCs. Mice tolerated a dose of 2 × 12 mg/kg (SN-38 equivalents) with only short-lived elevations in ALT and AST liver enzyme levels. Cynomolgus monkeys infused with 2 × 0.96 mg/kg exhibited only transient decreases in blood counts, although, importantly, the values did not fall below normal ranges.

CONCLUSIONS

The anti-Trop-2 hRS7-CL2A-SN-38 ADC provides significant and specific antitumor effects against a range of human solid tumor types. It is well tolerated in monkeys, with tissue Trop-2 expression similar to humans, at clinically relevant doses, and warrants clinical investigation.

Expression of the GA733 gene family and its relationship to prognosis in pulmonary adenocarcinoma

The GA733 gene family is composed of GA733-1 (TROP2) and GA733-2 (Ep-CAM), whose expression has been examined in various carcinomas and reported to be significantly associated with prognosis. The aim of this study was to investigate the expression of GA733 gene family members and to compare their prognostic significance in pulmonary adenocarcinoma. One hundred thirty paraffin-embedded specimens of small-sized pulmonary adenocarcinoma, less than 2 cm in diameter, were categorized using the classification of small-sized pulmonary adenocarcinoma devised by Noguchi et al. (Cancer 75:2844-2852, 1995) and examined immunohistochemically using a murine monoclonal antibody against Ep-CAM and a goat polyclonal antibody against TROP2. The patient survival rate was calculated using the Kaplan-Meier method. Ep-CAM and TROP2 were similarly expressed in many small-sized pulmonary adenocarcinomas. The expression of Ep-CAM was significantly related to a favorable outcome (p = 0.0185), whereas TROP2 tended to be expressed in cases with an unfavorable outcome (p = 0.0564), and was significantly associated with an unfavorable outcome in nonlepidic-type adenocarcinomas (p = 0.0125). Multivariate analysis showed that TROP2 overexpression and lymph node metastasis were independent prognostic markers. Although the two GA733 proteins share structural similarity, they appear to have opposite biological significances in small-sized adenocarcinomas. As the expression of TROP2 was detected in more poorly differentiated tumors, the protein may have oncogenic activity.

Short hairpin RNA-mediated silencing of TROP2 gene in gastric cancer BGC-823 cells

AIM: To construct eukaryotic expression vectors of short hairpin RNA (shRNA) specific for TROP2 gene and observe its silencing effect on TROP2 gene in BGC-823 cells.

METHODS: The eukaryotic expression vectors of short hairpin RNA (shRNA) specific for TROP2 were constructed by ligating pGensil1.1 plasmid (containing human U6 shRNA promoter) to TROP2-specific shRNA target sequences. After the resulting recombinant plasmids were transfected into BGC-823 cells, the cells were screened in medium containing G418 (at a concentration of 400 mg/L) for 24 h to obtain stably transfected cell strain. These stably transfected cells were then divided into W group (untransfected), HK group (transfected with random negative control plasmid), KB group (transfected with empty plasmid), T1 group, T2 group and T3 group. The expression of TROP2 gene in stably transfected cells was determined by real-time PCR and Western blot.

RESULTS: TROP2-specific shRNA target sequences were successfully inserted into eukaryotic expression vector pGensil1.1. The sequences of shRNAs inserted into the recombinant plasmids were identical to those expected. The expression levels of TROP2 mRNA and protein in cells transfected with recombinant plasmids were lower than those in untransfected cells or cells transfected with random negative control plasmid or empty plasmid. Compared with the T1 and T2 groups, TROP2-specific shRNA in the T3 group had the more strong inhibitory effect on the expression of TROP mRNA (8.79 ± 0.23 vs 9.54 ± 0.20, 9.57 ± 0.23) and protein (3.66 ± 0.11 vs 6.46 ± 0.36, 9.31 ± 0.11), and the differences were significant (all P < 0.05).

CONCLUSION: Eukaryotic expression vectors of shRNA specific for TROP2 gene are constructed successfully. The expression of TROP2 mRNA and protein is down-regulated in cells transfected with recombinant plasmids. Our study provides a new approach to the study of the function of TROP2 gene.

Frequent aberrant methylation of the promoter region of sterile alpha motif domain 14 in pulmonary adenocarcinoma

Aberrant methylation of promoter CpG islands is known to be a major inactivation mechanism of tumor-suppressor and tumor-related genes. In order to identify novel hypermethylated genes in early stage lung adenocarcinoma, we carried out methylated CpG island amplification, modified suppression subtractive hybridization, and methylation-specific polymerase chain reaction to identify aberrant methylation of CpG islands in the A/J mouse lung adenoma model, which histologically mimics the early stage of human pulmonary adenocarcinoma. Through methylated CpG island amplification, suppression subtractive hybridization, and differential screening, we detected five genes, three of which have human homologs. Two of them showed downregulation of their expression in human lung adenocarcinoma. Of these two genes, we selected sterile alpha motif domain 14 (SAMD14) and further analyzed its methylation status and expression level by methylation-specific polymerase chain reaction and quantitative real-time polymerase chain reaction. Most of the lung adenocarcinoma cell lines showed suppressed expression of SAMD14 together with hypermethylation at the promoter region, although an immortalized bronchial epithelium cell line (PL16B) did not show hypermethylation and did express SAMD14. The expression of SAMD14 in A549 was rescued by treatment with the demethylation agent 5-aza-2'-deoxycytidine. These data indicate that hypermethylation of the SAMD14 gene promoter region is associated with silencing of its expression. Hypermethylation at the CpG site of the SAMD14 promoter region was detected frequently in early invasive adenocarcinoma (8/24, 33.3%) but not in in situ adenocarcinoma (0/7, 0%) or normal lung tissue (0/31, 0%). Hypermethylation of the SAMD14 gene is a specific event in pulmonary adenocarcinogenesis and malignant progression.

TROP2: a novel prognostic marker in squamous cell carcinoma of the oral cavity

Squamous cell carcinoma is by far the most common type of cancer of the oral cavity, representing more than 90% of all oral cancers. Despite refinement of surgical techniques and adjuvant therapies, the prognosis for patients with oral squamous cell carcinoma remains poor. Identification of prognostic factors related to tumor biology might improve this assessment. Recently, the human trophoblast cell-surface antigen TROP2 was found to be highly expressed in colorectal cancer, correlating with aggressiveness and poor prognosis. Thus, the aim of this study was to investigate TROP2 expression and its prognostic impact in oral squamous cell carcinoma patients. TROP2 expression was examined by immunohistochemistry in a series of 90 patients on a tissue microarray of paraffin-embedded specimens. Survival was calculated using Kaplan-Meier estimates. Parameters found to be of prognostic significance in univariate analysis were verified in a multivariate Cox regression model. TROP2 overexpression was observed in 52 (58%) of the tumor samples. Kaplan-Meier curves showed that TROP2 overexpression was significantly associated with decreased overall survival (P<0.01). Overall survival gradually worsened with increasing TROP2 scores. By univariate analyses, no correlation with conventional clinicopathological features was found. Multivariate Cox regression analysis revealed TROP2 overexpression to be an independent factor predictive of poor disease outcome (P<0.01). These results demonstrate that TROP2 overexpression is an independent prognostic marker in patients with oral squamous cell carcinoma. TROP2 overexpression was detectable in 58% of the tumor samples, indicating it to be a potential novel therapeutic target in squamous cell carcinoma of the oral cavity.

A review of the S100 proteins in cancer

AIM

In the quest to reduce mortality and morbidity from cancer, there is continued effort to identify novel biomarkers to aid in the early detection and the accurate prediction of tumour behaviour. One group of proteins that is emerging as a potentially important group of markers in multiple tumour types is the S100 family. This review summarises the biological and clinical relevance of these proteins in relation to different tumour types.

METHODS

A literature search was performed using the PubMed database and the reference lists of relevant articles. Single case studies were excluded and only reports with a clinical relevance from 1961 to 2007 were included.

RESULTS

The search yielded over 1000 published articles and reports. Important reports and studies were reviewed, screened and tracked for further relevant publications. Only the most relevant publications are discussed with relation to individual members of the S100 family.

CONCLUSION

There is increasing evidence that altered expression of S100 family members is seen in many cancers including breast, lung, bladder, kidney, thyroid, gastric, prostate and oral cancers. S100 proteins are commonly up-regulated in tumours and this is often associated with tumour progression. In contrast S100A2, S100A11 and S100A9 have been documented as tumour suppressors in some cancers but as tumour promoters in others. This demonstrates the complexity of the family and variability of their functions. Although the precise roles of these proteins in cancer is still to be discovered many of the family are associated with promoting metastases through interactions with matrix metalloproteinases or by acting as chemoattractants. There is also evidence that some members can regulate transcription factors such as p53. S100B already has a role in a clinical setting in the diagnosis and therapeutic monitoring of malignant melanoma. As our understanding of this family develops it is likely that many more members will aid the diagnosis, monitoring and potential treatment of cancers in the future.

Decreased expression of gene cluster at chromosome 1q21 defines molecular subgroups of chemoradiotherapy response in esophageal cancers

PURPOSE

Resistance to preoperative chemoradiotherapy (CTXRT) in 75% of patients with esophageal adenocarcinoma (EAC) underscores the need for identification of biomarkers of CTXRT response. We previously noted an association between decreased expression of epidermal differentiation complex (EDC) genes S100A2 and SPRR3 at chromosome 1q21 and CTXRT resistance. In the current study, we did an in-depth investigation of the expression of 1q21-1q25 region genes to uncover the role of the EDC and its flanking genes in CTXRT response.

EXPERIMENTAL DESIGN

We compared 19 pretreatment EAC specimens with normal squamous mucosa for the expression of 517 genes at chromosome 1q21-1q25 and selected target genes based on their differential expression. Using the pathologic complete-response (pathCR) status of the resected specimens as a representation of CTXRT sensitivity, we assessed the association between the expression of target genes and CTXRT response and clinical outcomes.

RESULTS

On the basis of the expression levels of IVL, CRNN, NICE-1, S100A2, and SPPR3, genes within and in close proximity to the EDC, cancers were segregated into high (subgroup I) or low (subgroup II) expressers. Four of the five pathCRs were high expressers. Thus, low expressers, with one exception, were all nonresponders. Patients in subgroup I also had longer survival than those in subgroup II, although this result was not statistically significant owing to the small study number.

CONCLUSIONS

The expression levels of genes mapping within and close to the EDC define CTXRT response subgroups in EACs.