To date, nearly 120 patients with thoracic malignancies (mostly lung cancers) have received DAC), DP, or sequential DAC/DP infusions on protocols initiated in the Thoracic Oncology Section. Clinical toxicities and response to therapy have been assessed by CTCAE and RECIST criteria, respectively. Plasma DAC and DP levels have been evaluated by LC-MS and HPLC techniques. Quantitative RT-PCR, methylation-specific-PCR, immunohistochemistry, and ELISA techniques have been used to assess a variety of molecular endpoints in pre-and post-treatment tumor biopsies and sera. Micro-array techniques have been used to comprehensively examine gene expression profiles in laser-captured tumor cells from pre- and post treatment biopsies from 21 individuals receiving DAC, DP, or sequential DAC/DP infusions. Results of these arrays have been compared to data derived from analysis of laser-captured tumor cells and adjacent, histologically normal bronchial epithelia from 20 patients undergoing definitive lung cancer resections. Whereas no objective clinical responses have been observed, several patients have exhibited prolonged stabilization of disease following DAC, DP, or sequential DAC/DP infusions. Plasma DAC and DP concentrations have approximated threshold levels for gene induction and apoptosis in cultured lung cancer cells. Approximately 30% of patients receiving DAC or DP infusions have exhibited enhanced expression of NY-ESO-1, p16, p21, or acetylated histones H3 and H4 in tumor biopsies indicative of molecular response to therapy. Micro-array analyses have revealed complex, heterogeneous responses to DAC, DP, and DAC/DP in laser-captured lung cancer cells, with a shift of gene expression profiles toward those observed in histologically normal bronchial epithelia. These findings suggest that more prolonged exposures may be required to mediate cancer regressions. In additional studies, we have demonstrated that the cdk inhibitor, Flavopiridol (FLA), significantly enhances apoptosis mediated by DP, in part by abrogating HDAC-inhibitor-mediated up-regulation of p21. These findings provided the preclinical rationale for a protocol evaluating the toxicities and potential efficacy of sequential DP/FLA infusions in patients with thoracic malignancies. To date, 21 patients have received these infusions with acceptable toxicities. Although no tumor regressions have been noted as yet in this dose-escalation study, 7 patients have exhibited stabilization of disease lasting 4-12 months. These finding suggest a molecular response to therapy. The study will close after 4-6 additional patients have been treated. Collectively, this experience warrants further analysis of chromatin remodeling agents for treatment of thoracic malignancies, using schedules that enable chronic drug exposures. Although CT-X genes are coordinately de-repressed in lung cancers, immune responses to CT-X antigens are exceedingly rare in patients with these malignancies, due in part to levels of antigen expression that are below the threshold for immune recognition, as well as the presence of immunosuppressive T regulatory cells within the tumor and systemic circulation of these individuals. As such, we have sought to develop combinatorial regimens that will enhance immune responses to CT-X antigens in lung cancer patients. One potential strategy involves the use of epigenetically-modified autologous tumor cells to immunize lung cancer patients against a variety of CT-X antigens that potentially can be up-regulated in their respective primary cancers by systemic gene induction regimens. To date, no such efforts have been reported. To examine the potential feasibility of this approach, tissues/fluids from patients with thoracic tumors of various histologies were processed for primary culture. Sources of tumor cells included peritoneal fluid, endoscopic pleural or mediastinal biopsies, as well as CT-guided FNAs. To date, 26 cell lines have been established, several of which have been exposed to DAC+/-DP under exposure conditions exceeding those achievable in clinical settings. These experiments revealed robust, heterogeneous CT-X gene induction;following drug treatment, primary HLA-A*0201 cancer lines were recognized by allogeneic PBL expressing HLA-A*0201 T cell receptors for NY-ESO-1 and MAGE-A3. These studies provided the preclinical rationale for two IRB-approved protocols evaluating the use of autologous epigenetically-modified tumor cell vaccines as a means to broadly immunize thoracic oncology patients against multiple CT-X antigens following complete resection of their malignancies. Various aspects of the preclinical studies pertaining to these trials have been presented in oral or poster format at the Annual Meeting of the American Association of Thoracic Surgery, as well as an international cancer epigenetics conference. A manuscript describing this experience is being prepared for publication. An alternative, and perhaps less expensive strategy involves utilization of allogeneic cancer cells, which express high levels of numerous clinically relevant CT-X antigens without pharmacologic manipulation. In ongoing experiments, we have observed that K562 erythroleukemia cells broadly express CT-X antigens. Furthermore, H1299 lung cancer cells express even more CT-X antigens at higher levels than K562;both cell lines express CT-X antigens at levels significantly higher than testes controls. Two protocols have been initiated to ascertain the feasibility of using K562 cells constitutively expressing GM-CSF (K562-GM) to induce immunity to CT-X antigens in patients undergoing complete resection of primary thoracic malignancies or those with extra thoracic neoplasms metastatic to the chest. These vaccines are administered monthly in conjunction with metronomic oral cyclophosphamide and celecoxib to inhibit/deplete immunosuppressive T regulatory cells. To date 6 patients have received vaccinations on these recently initiated protocols. Additional vaccine efforts utilizing H1299 cells, administered either as whole cells or lysates in Iscomatrix (a potent adjuvant) will commence as soon as the master cell bank has been established and IND secured.
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