Systemic but not topical TRAIL-expressing mesenchymal stem cells reduce tumour growth in malignant mesothelioma.

Malignant pleural mesothelioma is a rare but devastating cancer of the pleural lining with no effective treatment. The tumour is often diffusely spread throughout the chest cavity, making surgical resection difficult, while systemic chemotherapy offers limited benefit. Bone marrow-derived mesenchymal stem cells (MSCs) home to and incorporate into tumour stroma, making them good candidates to deliver anticancer therapies. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a pro-apoptotic molecule that selectively induces apoptosis in cancer cells, leaving healthy cells unaffected. We hypothesised that human MSCs expressing TRAIL (MSCTRAIL) would home to an in vivo model of malignant pleural mesothelioma and reduce tumour growth. Human MSCs transduced with a lentiviral vector encoding TRAIL were shown in vitro to kill multiple malignant mesothelioma cell lines as predicted by sensitivity to recombinant TRAIL (rTRAIL). In vivo MSC homing was delineated using dual fluorescence and bioluminescent imaging, and we observed that higher levels of MSC engraftment occur after intravenous delivery compared with intrapleural delivery of MSCs. Finally, we show that intravenous delivery of MSCTRAIL results in a reduction in malignant pleural mesothelioma tumour growth in vivo via an increase in tumour cell apoptosis.

A phase II trial of single oral FGF inhibitor, AZD4547, as second or third line therapy in malignant pleural mesothelioma.

OBJECTIVES: Currently, there is no optimal salvage therapy for patients with malignant pleural mesothelioma (MPM) who relapse after treatment with first-line chemotherapy. In line with the strong preclinical rationale for targeting fibroblast growth factor receptor (FGFR) signalling in malignant mesothelioma, we conducted a phase II study assessing the efficacy of AZD4547, an oral tyrosine multi-kinase FGFR 1-3 inhibitor, as a second or third-line treatment. MATERIALS AND METHODS: We conducted a single-center, open-label, single-arm phase II study of AZD4547 in eligible patients with confirmed, measurable MPM and radiological progression after first or second-line systemic chemotherapy. Patients received continuous, twice-daily oral AZD4547 on a 3-weekly cycle. The primary end point was 6-month progression free survival (PFS6). Response was assessed with CT scan every 6 weeks according to the modified RECIST criteria for mesothelioma (mRECIST) and toxicities were also assessed. The study used a Simon's two-stage design: 26 patients would be recruited to the first stage and more than 7 (27 %) of 26 patients were required to achieve PFS6 to continue to stage two, for a potential total cohort of 55 patients. RESULTS: 3 of 24 patients (12 %) were progression-free at 6 months. Hence, the study fulfilled stopping criteria regardless of further recruitment and warranted discontinuation. The most common toxicities (across all grades) were hyperphosphatemia, xerostomia, mucositis, retinopathy, dysgeusia, and fatigue. Maximum toxicities were grade 2 or below for all patients across all cycles. There was no association between tumour BAP1 protein loss and clinical outcomes. CONCLUSIONS: The FGFR 1-3 inhibitor AZD4547 did not demonstrate efficacy in patients with MPM who had progressed after first line treatment with platinum-based chemotherapy.

Transforming growth factor beta induces vascular endothelial growth factor elaboration from pleural mesothelial cells in vivo and in vitro.

Vascular endothelial growth factor (VEGF) increases vascular permeability and is important in pleural effusion formation. In studies using transforming growth factor beta (TGF-beta) to produce pleurodesis, we observed that although TGF-beta was more effective than talc or doxycycline, it induced transient production of large pleural effusions. We hypothesized that TGF-beta stimulates VEGF production in pleural tissues in vivo, and by mesothelial cells in vitro. New Zealand White rabbits (n = 33) were given TGF-beta(2) (1.7 or 5.0 microg), talc (400 mg/kg), doxycycline (10 mg/kg), or buffer intrapleurally. Pleural fluid was collected at 24 h. Intrapleural injection of TGF-beta(2) induced a dose-dependent increase in VEGF production. The pleural fluid VEGF level was 2-fold higher in rabbits given 5.0 microg of TGF-beta(2) than in those given 1.7 microg of TGF-beta(2) and 3-fold higher than in those given buffer. VEGF levels were higher after the injection of TGF-beta(2) than after administration of talc or doxycycline. The pleural fluid VEGF correlated significantly with the volume of pleural effusions (r = 0.79, p < 0.00001). In vitro, TGF-beta(2) stimulated a dose-dependent increase in VEGF production from murine pleural mesothelial cells. At 4 and 24 h, TGF-beta(2), but not talc or doxycycline, induced a significant increase in VEGF, when compared with controls. The mesothelial cell VEGF production was significantly reduced by anti-TGF-beta antibody in the TGF-beta(2), talc, and control (buffer and medium) groups. In conclusion, mesothelial cells are an important source of VEGF. TGF-beta increases the VEGF production by mesothelial cells in vivo and in vitro.

Transforming growth factor-beta2 induces pleurodesis significantly faster than talc.

Transforming growth factor-beta2 (TGF-beta2) has recently been shown to produce effective pleurodesis in rabbits. Conventional pleurodesing agents such as talc act by inducing pleural injury, which results in acute inflammation and fibrosis. TGF-beta2 is a profibrotic cytokine capable of producing fibrosis without inducing significant pleural inflammation. We hypothesize that intrapleural administration of TGF-beta2 would (1) produce an effective pleurodesis faster; (2) stimulate more collagen deposition, and (3) induce less inflammation when compared with intrapleural injection of talc. Thirty rabbits were divided into two groups and given either TGF-beta(2) (1.7 microg) or talc slurry (400 mg/kg) via a chest tube. Five rabbits from each group were killed at Days 1, 4, and 7. Gross pleurodesis was graded from 1 (none) to 8 (complete symphysis). The microscopic pleural inflammation and fibrosis were graded from 0 to 4. Pleural thickening and the total area of collagen deposition were compared. Intrapleural injection of TGF-beta2 produced effective pleurodesis within 7 d (median pleurodesis score = 7 at Day 7). At Day 7, TGF-beta2 induced significantly more collagen deposition (19.4 +/- 19.6% versus 4.6 +/- 2.9% of total area of pleura at Day 7), higher pleural fibrosis score (3.0 +/- 1.0 versus 1.8 +/- 0.5), and pleural thickness (286 +/- 191 versus 85 +/- 37 microm) than did talc. There was no difference in the degree of pleural inflammation between the two groups at Day 7 (2.6 +/- 0.9 for TGF-beta2 versus 2.4 +/- 0.6 for talc) or at any other time points. In conclusion, the intrapleural administration of TGF-beta2 produced excellent pleurodesis in rabbits at a rate faster than talc slurry and all other pleurodesing agents investigated before. TGF-beta2 stimulated more collagen deposition without inducing excess inflammation when compared with talc slurry. TGF-beta2 may have advantages over talc slurry in the management of recurrent pleural effusion and pneumothorax.