Morphological aspects of carcinogenesis in the lung

Recurrence of squamous cell lung carcinoma is associated with the co-presence of reactive lesions in tumor-adjacent bronchial epithelium

Recurrences occur in 30 % of lung cancer patients after radical therapy; however, known prognostic factors are not always effective. In this study, we investigated whether the frequency of squamous non-small cell lung cancer (NSCLC) recurrence depends on the presence of reactive lesions in tumor-adjacent bronchial epithelium. Specimens of adjacent lung tissue from 104 patients with squamous NSCLC were used for the determination of basal cell hyperplasia (BCH) and squamous metaplasia (SM) and for the analysis of the expression of Ki-67, p53, Bcl-2, and CD138. We found that recurrence was observed in 36.7 % of patients with BCH combined with SM (BCH + SM+) in the same bronchus, compared with 1.8 % in patients with isolated BCH (BCH + SM-; odds ratio (OR) 31.26, 95 % confidence interval (CI) 3.77-258.60; p = 0.00002). The percentage of Ki-67-positive cells was significantly higher in BCH + SM+ than in BCH + SM- (34.9 vs. 18.3 %; effect size 2.86, 95 % CI 2.23-3.47; p = 0.003). P53 expression was also more significant in BCH + SM+ than in BCH + SM- (14.4 vs. 9.6 %; effect size 1.22, 95 % CI 0.69-1.76; p = 0.0008). In contrast, CD138 expression was lower in BCH + SM+ than in BCH + SM- (21.8 vs. 38.5 %; effect size -6.26, 95 % CI -7.31 to -5.22; p = 0.003). Based on our results, we concluded that the co-presence of reactive bronchial lesions is associated with the development of recurrent squamous NSCLC and may be a negative prognostic indicator. In addition, significant differences in Ki-67, p53, and CD138 expression exist between isolated BCH and BCH combined with SM that probably reflect part of biological differences, which could relate to the mechanism of lung cancer recurrence.

Histological types and significance of bronchial epithelial dysplasia

Pulmonary epithelium is known to undergo a preneoplastic process prior to the development of lung carcinoma. Squamous dysplasia and atypical adenomatous hyperplasia have been identified and classified as preinvasive lesions of squamous cell carcinoma and peripheral pulmonary adenocarcinoma, respectively. However, these commonly recognized preinvasive lesions do not completely explain the development of all histological types of lung carcinoma. By examining 114 resection lung specimens, we concluded that there are four histological patterns of bronchial epithelial dysplasia based on morphological features (basal cell dysplasia, columnar cell dysplasia, bronchial epithelial dysplasia with transitional differentiation, and squamous dysplasia). The histological patterns were further characterized by immunohistochemistry. Basal cell dysplasia was focally positive for cytokeratin (CK) 17 and 10/13; columnar cell dysplasia was generally positive for CK7, 8, and 18; bronchial epithelial dysplasia with transitional differentiation had a heterogeneous immunoprofile, while squamous dysplasia was positive for CK10/13 and focally positive for CK17. Various degrees of abnormal expression of p53 and Ki-67 were found in the different types of bronchial epithelial dysplasia. The cases were divided into three groups based on degree and extent of bronchial epithelial dysplasia. By Crosstabs McNemar test, the Mann-Whitney U-test (for two independent groups), the Kruskal-Wallis one-way nonparametric ANOVA (for >2 independent groups) and Spearman correlation analysis, the degree and extent of bronchial epithelial dysplasia was shown to be positively correlated with the incidence of bronchogenic carcinoma and multifocal primary lung carcinoma (P<0.05). These findings indicated the following: (1) bronchial epithelium can develop various patterns of dysplasia with abnormal/ambiguous cell differentiation and abnormal expressions of p53 and Ki-67. Thus, these bronchial epithelial dysplastic lesions may represent a preneoplastic process. (2) The degree of bronchial epithelial dysplasia may significantly predispose individuals to bronchogenic carcinoma and multifocal primary lung carcinoma.

Roles for USF-2 in lung cancer proliferation and bronchial carcinogenesis

The upstream stimulatory factors USF-1 and USF-2 dimerize to regulate transcription through E-box motifs in target genes. Although widely expressed, they can mediate tissue-specific transcription and we previously reported that USF-2 can enhance transcription of arginine vasopressin, a neuropeptide growth factor in small cell lung cancer. Here we determine the expression and role of USF-2 in lung cancer subtypes and examine USF-2 distribution in the bronchial epithelium. For a panel of 12 cell lines and 10 frozen human tumour samples, immunoblotting demonstrated that USF-2 expression was more frequent and abundant in small cell lung cancer than in non-small cell lung cancer. An immunohistochemical study of 108 formalin-fixed and paraffin-embedded human samples was undertaken to localize USF-2 expression and included 44 small cell and 32 non-small cell lung cancers, and 32 samples with bronchial dysplasia. USF-2 was restricted to ciliated cells in normal bronchial epithelium, but was more strongly expressed in dysplastic epithelium (72%) and certain lung cancer types, including small cell lung cancer (71%), squamous cell carcinoma (69%) and a large cell neuroendocrine carcinoma, but was less common in adenocarcinoma (11%). In a small series, expression was assessed adjacent to positively staining tumours; in phenotypically normal bronchial tissues, USF-2 was more highly expressed at 1 cm than at 5 cm from the tumour. Transient USF-2 overexpression in non-small cell lung cancer cell lines significantly stimulated in vitro cell proliferation; this response was most apparent for NCI-H460 (p < 0.005), reducing the mean cell doubling time from 19 to 16 h. Dominant-negative USF-2 mutants had no significant effect on cell growth. Taken together, these data suggest that USF-2 represents a relatively early molecular marker for the development of bronchial dysplasia and non-adenocarcinoma lung cancer. USF may also play a role in bronchial carcinogenesis, perhaps through promoting cell proliferation, although the genes through which this is regulated remain to be determined.

Neuro-endocrine neoplasms as a result of gene desuppression rather than of a specific cell type of origin

Neuroendocrine differentiation more closely approximates a process of acquisition of features that ambiguously recapitulate certain cellular biologic properties that transgress normal lines of differentiation as these are generally recognized. In fact, it might be more realistic to consider neuroendocrine tumors the result of a process of progressive desuppression via pathways of altered gene expression that would perhaps reflect basic and dynamic aspects of neoplastic transformation and progression in general. In a final analysis, the character and degree of differentiation of a neoplasm might actually often constitute an anomalous combination of features outside the range of normal differentiation pathways and more an expression of an assorted mixture of partially suppressed or desuppressed gene expression profiles as these affect neoplastic cell pathobiology.