Nadine Martinet

Squamous cell carcinoma (SCC) of the lung is a frequent and aggressive cancer type. Gene amplifications, a known activating mechanism of oncogenes, target the 3q26-qter region as one of the most frequently gained/amplified genomic sites in SCC of various types. Here, we used array comparative genomic hybridization to delineate the consensus region of 3q26.3 amplifications in lung SCC. Recurrent amplifications occur in 20% of lung SCC (136 tumors in total) and map to a core region of 2 Mb (Megabases) that encompasses SOX2, a transcription factor gene. Intense SOX2 immunostaining is frequent in nuclei of lung SCC, indicating potential active transcriptional regulation by SOX2. Analyses of the transcriptome of lung SCC, SOX2-overexpressing lung epithelial cells and embryonic stem cells (ESCs) reveal that SOX2 contributes to activate ESC-like phenotypes and provide clues pertaining to the deregulated genes involved in the malignant phenotype. In cell culture experiments, overexpression of SOX2 stimulates cellular migration and anchorage-independent growth while SOX2 knockdown impairs cell growth. Finally, SOX2 over-expression in non-tumorigenic human lung bronchial epithelial cells is tumorigenic in immunocompromised mice. These results indicate that the SOX2 transcription factor, a major regulator of stem cell function, is also an oncogene and a driver gene for the recurrent 3q26.33 amplifications in lung SCC.

BACKGROUND: Retinoids can suppress carcinogenesis in high-risk non-neoplastic bronchial lesions and can reduce the risk of second primary non-small-cell lung cancer (NSCLC). The effects of retinoids are mediated by nuclear receptors, i.e., the retinoic acid receptors (RARalpha, RARbeta, and RARgamma) and the retinoid X receptors (RXRalpha, RXRbeta, and RXRgamma). We investigated whether abnormalities in the in vivo expression of retinoid receptors are observed in NSCLC. METHODS: Expression of retinoid receptors in paired specimens of normal and cancerous tissues from the lungs of 76 patients with NSCLC was studied by use of antiretinoid receptor antibodies (except those against RXRgamma) and immunohistochemistry. RAR messenger RNAs were analyzed by use of in situ hybridization and by reverse transcription-polymerase chain reaction (RT-PCR). Samples were also studied for loss of heterozygosity (LOH) at chromosome 3p24. All P values are two-sided. RESULTS: All studied receptors were expressed in normal lung cells and in high- risk non-neoplastic lesions. In tumor cells, overexpression of RXRalpha and RARalpha was frequently observed. In contrast, RXRbeta expression decreased in 18% of the tumor specimens. Furthermore, there was a marked decrease in the expression of RARbeta in 63% of the tumors (P<.0001). Decreased expression of RARgamma was observed by RT-PCR in 41% of the tumors (P<.0001). LOH at 3p24 was observed in 41% of the tumor specimens from informative patients and in 20% of the non-neoplastic lesions. CONCLUSIONS: Expression of RARalpha and RXRalpha is either normal or elevated in NSCLC. In contrast, a large percentage of tumors show a marked decrease in the expression of RARbeta, RARgamma, and RXRbeta as well as a high frequency of LOH at 3p24, which was also observed in non-neoplastic lesions. These data suggest that altered retinoid receptor expression may play a role in lung carcinogenesis.

Among patients with resected non-small cell lung carcinoma, about 50% will present a tumor recurrence. Thus, it would be of major importance to be able to predict and try to prevent these relapses by an active chemotherapy and/or radiotherapy. In an attempt to answer this question, the tumors of 227 patients with a surgically resected non-small cell lung carcinoma were evaluated as follows: tumors were classified as squamous cell carcinoma (n = 132) or adenocarcinoma (n = 95), and tumor differentiation was evaluated for each type. Then, all tumors were classified in respect to their pathological TNM staging (WHO) and screened by immunohistochemistry for the detection of the expression of the following antigens: Bcl-2, A+B+H blood group antigens, c-erb-b2, p53, and Pan-Ras antigens. Furthermore, adenocarcinomas were screened for the presence of point mutations in Ki-Ras codons 1-31. Finally, the patient blood group was defined, and patient survival was analyzed using nonparametric tests and proportional hazard Cox models. Using Kaplan-Meier survival curves, disease pathological TNM staging was shown to be a strong predictive factor of survival for both squamous cell carcinoma and adenocarcinoma. Patients with squamous cell carcinoma experienced fewer relapses than those with adenocarcinoma (42% versus 63%; P = 0.0002) and had a significantly better survival. All evaluated antigens were more often present in squamous cell carcinoma than in adenocarcinoma except for Pan-Ras (three times more frequent in adenocarcinoma). In patients with squamous cell carcinoma, only tumor staging had a significant prognosis value (P = 0.01). In patients with lung adenocarcinoma, a well-differentiated tumor (P = 0.009) as well as a positive Bcl-2 staining (P = 0.009) and an A+B+H antigen tumor staining (P = 0.024) were associated with a better survival. In contrast, patients with a stage I or II disease and a p53-positive tumor staining and patients with the O blood group (P = 0.01) had a shorter survival. Interestingly, no relation with patient survival was related to c-erb-b2 and Pan-Ras staining. Finally, 12 point mutations were found out of 81 tumors (15%) evaluated for Ki-Ras codons 1-31; they involved codon 12 but also 8, 14, and 15 without any relationship to survival. In respect to lung adenocarcinoma, using Cox proportional hazard models stratified on tumor staging, the following markers were shown to be related to survival: (a) Independent markers of longer survival (ie., high histological degree of tumor differentiation and positive Bcl-2 and A+B+H blood group antigen expression by tumor cells); and (b) Independent markers of shorter survival (i.e., O blood group for all patients and p53 tumor staining in patients with stage I and II diseases). This study suggests that, in patients who undergo surgery for lung adenocarcinoma, the presence or absence of these criteria could be used to define a subset of patients who may benefit from a more specific follow-up.