Lung cancer

Type I insulin-like growth factor receptor induces pulmonary tumorigenesis

Despite the type I insulin-like growth factor receptor (IGF-IR) being highly expressed in more than 80% of human lung tumors, a transgenic model of IGF-IR overexpression in the lung has not been created. We produced two novel transgenic mouse models in which IGF-IR is overexpressed in either lung type II alveolar cells (surfactant protein C [SPC]-IGFIR) or Clara cells (CCSP-IGFIR) in a doxycycline-inducible manner. Overexpression of IGF-IR in either cell type caused multifocal adenomatous alveolar hyperplasia with papillary and solid adenomas. These tumors expressed thyroid transcription factor 1 and Kruppel-like factor 5 in most tumor cells. Similar to our previous work with lung tumors that developed in the mouse mammary tumor virus-IGF-II transgenic mice, the lung tumors that develop in the SPC-IGFIR and CCSP-IGFIR transgenic mice expressed high levels of the cyclic adenosine monophosphate response element binding protein that was localized primarily to the nucleus. Although elevated IGF-IR expression can initiate lung tumor development, tumors can become independent of IGF-IR signaling as IGF-IR down-regulation in established tumors produced tumor regression in some, but not all, of the tumors. These findings implicate IGF-IR as an important initiator of lung tumorigenesis and suggest that the SPC-IGFIR and CCSP-IGFIR transgenic mice can be used to further our understanding of human lung cancer and the role IGF-IR plays in this disease.

Epidermal growth factor receptor mutations in lung cancers

In 2004, two groups reported somatic mutations in the gene for the epidermal growth factor receptor (EGFR) in patients with non-small cell lung cancer (NSCLC), which were highly correlated with the clinical response to the anticancer drug, gefitinib. Since then, a tremendous amount of knowledge has accumulated, and sheds light on significant oncological properties as well as the clinical relevance of this mutation, which could be applicable to other malignancies. The EGFR mutations are distributed throughout the kinase domain, but a deletion in exon 19 and the point mutation L858R in exon 21 account for approximately 90%, which confer a greater response to gefitinib treatment, compared with other types of EGFR mutations. These EGFR mutations in the tyrosine kinase domain are seldom acquired in cancers of the other organs and the mutations preferentially involve a subset of lung cancers, which are clinicopathologically characterized by female sex, non-smoking, adenocarcinoma histology and East Asian ethnicity. In Japan, the EGFR mutations are detected in approximately 30% of overall NSCLC and approximately 40% of surgically resected adenocarcinomas. The morphological features of adenocarcinomas harboring the mutations were reported to be frequent in those with bronchioloalveolar features, but it is suggested that the cellular lineage of the putative original cells of the cancers refines the subset more clearly. In the present study the current knowledge of EGFR mutations is reviewed, insights from which raise many further questions, and thus suggest new directions for future research.

Erlotinib for frontline treatment of advanced non-small cell lung cancer: a phase II study

PURPOSE

Erlotinib has proven activity in pretreated patients with advanced non-small cell lung cancer (NSCLC). We evaluated erlotinib in the frontline treatment of advanced NSCLC and assessed biological predictors of outcome.

EXPERIMENTAL DESIGN

In this phase II study, chemotherapy-naive patients with stage IIIB/IV NSCLC received oral erlotinib (150 mg/d) until disease progression or unacceptable toxicity occurred. Tumor response was assessed every 6 weeks, and samples were analyzed for potential molecular markers of treatment response and survival. The primary end point was the proportion of patients without disease progression after 6 weeks of treatment.

RESULTS

Fifty-three patients were eligible. The overall rate of nonprogression at 6 weeks was 52.8% (28 of 53 patients). Tumor response rate was 22.7%, with 1 complete response, 11 partial responses, and 16 cases of stable disease. Responses were seen across most patient clinical characteristics. The median duration of tumor response was 333 days; median overall survival was 391 days; and median time to disease progression was 84 days. Erlotinib was well tolerated, the main treatment-related adverse events being mild-to-moderate rash and diarrhea. Histologic material for biological studies was available in 29 cases. Four of five responders and one patient with stable disease had a classic epidermal growth factor receptor tyrosine kinase mutation. Two progressing patients exhibited epidermal growth factor receptor point mutations (one with T790M mutation), and K-ras mutations were detected in 10 nonresponders.

CONCLUSIONS

Erlotinib shows significant antitumor activity in the first-line treatment of advanced NSCLC and may be a viable alternative to chemotherapy. Patient selection cannot easily be based on clinical or biological variables.