Assay of lapatinib in murine models of cigarette smoke carcinogenesis

Abstract

Lapatinib, a dual tyrosine kinase inhibitor targeting the epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER-2), is prescribed for the treatment of patients with metastatic breast cancer overexpressing HER-2. Involvement of this drug in pulmonary carcinogenesis has been poorly investigated. We used murine models suitable to evaluate cigarette smoke-related molecular and histopathological alterations. A total of 481 Swiss H mice were used. The mice were exposed to mainstream cigarette smoke (MCS) during the first four months of life. After 10 weeks, MCS caused an elevation of bulky DNA adducts, oxidative DNA damage and an extensive downregulation of microRNAs in lung. After four months, an increase in micronucleus frequency was observed in peripheral blood erythrocytes. After 7.5 months, histopathological alterations were detected in the lung, also including benign tumors and malignant tumors, and in the urinary tract. A subchronic toxicity study assessed the non-toxic doses of lapatinib, administered daily with the diet after weaning. After 10 weeks, lapatinib significantly attenuated the MCS-related nucleotide changes and upregulated several low-intensity microRNAs in lung. The drug poorly affected the MCS systemic genotoxicity and had modest protective effects on MCS-induced preneoplastic lesions in lung and kidney, when administered under conditions that temporarily mimicked interventions either in current smokers or ex-smokers. On the other hand, it caused some toxicity to the liver. Thus, on the whole, lapatinib appears to have a low impact in the smoke-related lung carcinogenesis models used, especially in terms of tumorigenic response.

Fig. 1.

Scatter-plots relating the expression of 1135 pulmonary miRNAs, as evaluated by microarray analysis, in mice receiving dietary lapatinib with that of sham-exposed mice (A), in MCS-exposed mice compared with sham-exposed mice (B), and in MCS-exposed mice treated with lapatinib with MCS-exposed mice in the absence of the drug (C). Each dot represents a miRNA, whose expression intensity can be inferred from the position on the x and y axes. The central diagonal lines indicate equivalence in the intensity of miRNA expression in the mice treated as indicated in the x and y axes. The outer diagonal lines indicate 2-fold differences in miRNA expression between the indicated treatments. The dots falling in the upper left areas refer to miRNAs whose expression was >2-fold higher in the mice treated as indicated in the y axis, whereas the dots falling in the bottom right areas refer to miRNAs whose expression was >2-fold higher in the mice treated as indicated in the x axis.

Fig. 2.

Bidimensional principal component analysis showing the allocation of sham-exposed mice, lapatinib-treated mice, MCS-exposed mice, and MCS-exposed mice treated with lapatinib according to the overall expression of 1135 pulmonary miRNAs.