Molecular Intervention in Thoracic Malignancies

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Pulmonary, esophageal, and pleural malignancies arise via multistep mechanisms in cancerization fields. Although their etiologies may differ, these malignancies exhibit universal molecular themes including aberrant signal transduction via ras pathways, inactivation of the Rb and p53 tumor suppressor pathways, and expression of telomerase, all of which appear critical for malignant transformation. In addition to disrupting cell cycle regulation, oncogene and tumor suppressor gene mutations influence the metastatic phenotype of thoracic neoplasms by modulating expression of adhesion molecules, matrix metalloproteinases, as well as proangiogenic ligands such as vascular endothelial growth factor. Global derangements in chromatin structure and DNA methylation which silence a variety of tumor suppressor genes facilitate de novo expression of several cancer testis antigens in thoracic malignancies. Mutations involving erbB1/2, cyclin D, Rb, p16, p14/ARF, and p53 are attractive targets for intervention in thoracic malignancies and their precursor lesions; SV40 oncoproteins may be unique targets for molecular intervention in malignant pleural mesotheliomas. In published studies we have demonstrated that abrogation of erbB signal transduction by 17-AAG and related compounds markedly enhances sensitivity to chemotherapeutic agents and inhibits the metastatic phenotype of lung and esophageal cancer cells. Additional laboratory efforts have focused on the analysis of gene induction in thoracic malignancies mediated by DNA demethylating agents and histone deacetylase (HDAC) inhibitors. We have observed that under exposure conditions that facilitate expression of tumor suppressor genes such as p16, 5 aza 2' deoxycytidine (DAC) mediates induction of MAGE-3 and NY-ESO-1 cancer testis antigens. In addition we have demonstrated that DAC-mediated target gene induction can be augmented by the HDAC inhibitor Depsipeptide FR901228 (DP). Furthermore, we have shown that following exposure to DAC, or sequential DAC/DP, cancer cells can be recognized by cytolytic T lymphocytes specific for NY-ESO-1, and that sequential DAC/DP treatment mediates profound proapoptotic effects in cancer cells but not cultured normal human bronchial epithelial cells. These data have provided the preclinical rationale for two active clinical trials examining gene induction mediated by DAC and DP, as well as another protocol evaluating sequential DAC/DP infusion in thoracic oncology patients scheduled to commence in the near future. Having observed that DAC, DP, and sequential DAC/DP mediate growth arrest irrespective of histology or tumor suppressor gene status, we have utilized cDNA microarray techniques to examine the mechanisms by which these agents mediate apoptosis preferentially in cancer cells. Thus far, this analysis has revealed highly complex effects of these agents in cancer cells without obvious patterns of induction relative to genotype. Several novel mechanisms have been identified, and results pertaining to some of these experiments have been submitted for publication. In addition to our in vitro experiments, we have used cDNA microarray techniques to analyze gene expression in tissue biopsy specimens following Decitabine, or Depsipeptide treatment of lung cancer patients. We can reliably amplify mRNA from FNA and bronchoscopic biopsy specimens from patients on these trials. Because the evaluation of gene induction in cancer specimens may be adversely affected by stromal contamination, current efforts are underway to optimize laser capture microdissection and RNA amplification techniques in order to enhance the specificity of genetic analysis.Thus far, evidence of target gene induction has been observed in several patients on these trials. Nearly one-third of all patients dying from extrathoracic malignancies suffer from pulmonary metastases. In preclinical studies, we have evaluated the pharmacokinetics and acute toxicity of paclitaxel administered by retrograde isolated lung perfusion techniques, and have observed significant enhancement of paclitaxel cytotoxicity in cancer cells by moderate hyperthermia. These experiments have provided the preclinical rationale for an ongoing Phase I study. Furthermore, we have extended our efforts pertaining to the regional treatment of pulmonary malignancies by examining the toxicity and potential efficacy of cytotoxic agents administered via novel aerosolization techniques. The following clinical protocols submitted by the Thoracic Oncology Section are open for patient accrual: 1) Phase I Study of Decitabine Mediated Induction of Tumor Antigen and Tumor Suppressor Gene Expression in Patients with Cancers Involving the Lungs, Esophagus, or Pleura. 2) Phase II Study of Gene Induction Mediated by Four-Hour Depsipeptide Infusion in Lung Cancer Patients. 3) Phase I Study of Retrograde Isolated Lung Perfusion with Paclitaxel and Moderate Hyperthermia in Patients with Unresectable Pulmonary Malignancies. 4) Phase I and Clinical Pharmacologic Study of Inhaled Doxorubicin in Adults with Advanced Solid Tumors Affecting the Lungs.