The cell therapy industry has grown rapidly over the past 3 decades, and multiple clinical trials have been performed to date covering a wide range of diseases. The most frequently used cell is mesenchymal stromal cells (MSCs), which have been used largely for their anti-inflammatory actions and in situations of tissue repair and although they have demonstrated a good safety profile, their therapeutic efficacy has been limited. In addition to these characteristics MSCs are being used for their homing and engraftment properties and have been genetically modified to enable targeted delivery of a variety of therapeutic agents in both malignant and nonmalignant conditions. This review discusses the science and technology behind genetically modified MSC therapy in malignant disease and how potential problems have been overcome to enable their use in two novel clinical trials in metastatic gastrointestinal and lung cancer.

Background:Tumours contain stem-like, side population (SP) cells, which have increased tumorigenic potential, resistance to traditional therapies and may be responsible for treatment failures and relapse in patients.Methods:Mesenchymal stem cells (MSCs) were engineered to express the apoptotic ligand, TNF-related apoptosis-inducing ligand (TRAIL). Squamous (H357) and lung (A549) cancer cell lines were sorted into side and non-side populations (non-SP) by Hoechst flow cytometry. The survival and growth of both SP and non-SP cancer populations, in conjunction with TRAIL-expressing MSCs and mitoxantrone chemotherapy, were assessed by flow cytometry and colony forming ability.Results:Mesenchymal stem cells expressing TRAIL migrate to tumours and reduce the growth of primary cancers and metastases. This report demonstrates that these cells cause apoptosis, death and reduced colony formation of the SP of squamous and adenocarcinoma lung cancer cells and are synergistic when combined with traditional chemotherapy in apoptosis induction.Conclusions:The sensitivity of putative cancer stem cells to TRAIL-expressing MSCs, suggests their possible role in the prevention of cancer relapse.

Malignant mesothelioma (MM) is poorly responsive to systemic cytotoxic chemotherapy and invariably fatal. Here we describe a screen of 94 drugs in 15 exome-sequenced MM lines and the discovery of a subset defined by loss of function of the nuclear deubiquitinase BRCA associated protein-1 (BAP1) that demonstrate heightened sensitivity to TRAIL (tumour necrosis factor-related apoptosis-inducing ligand). This association is observed across human early passage MM cultures, mouse xenografts and human tumour explants. We demonstrate that BAP1 deubiquitinase activity and its association with ASXL1 to form the Polycomb repressive deubiquitinase complex (PR-DUB) impacts TRAIL sensitivity implicating transcriptional modulation as an underlying mechanism. Death receptor agonists are well-tolerated anti-cancer agents demonstrating limited therapeutic benefit in trials without a targeting biomarker. We identify BAP1 loss-of-function mutations, which are frequent in MM, as a potential genomic stratification tool for TRAIL sensitivity with immediate and actionable therapeutic implications.

C-reactive protein (CRP) is a sensitive marker of inflammation and tissue damage. We aimed to describe CRP responses in HIV-infected patients presenting with Pneumocystis pneumonia (PCP), bacterial pneumonia (BP) and pulmonary tuberculosis (TB) and, in patients with PCP, to identify if elevated CRP has prognostic significance. Data obtained by case-note review of consecutive HIV-infected adults with acute respiratory episodes included admission CRP (elevated >5 mg/L), haemoglobin, white blood count, CD4 count and partial pressure of oxygen in the blood (PaO(2)), presence of pulmonary co-pathology/intercurrent infection and outcome (survival). Median (range) CRP in patients with BP = 120 mg/L (<5-620 mg/L), TB = 44 mg/L (<5-256.3 mg/L) and PCP = 35 mg/L (<5-254 mg/L). CRP was elevated in 93/103 (90.3%) patients with PCP; six patients died; and all had an elevated CRP. PaO(2) and CRP values were associated as follows: average CRP levels declined by 10% (95% confidence interval [CI] 0.20%) per kPa increase in PaO(2) = 0.002. Factors associated with death were higher CRP, odds ratio (OR) (95% CI) = 5.30 (1.61 to 17.51) per 100 mg/L increase, P = 0.006 and haemoglobin, OR (95% CI) = 0.52 (0.29 to 0.93) per g/dL, P = 0.033. CRP is elevated in the majority of HIV-infected patients with PCP, BP and TB. Admission CRP measurement lacks specificity, but in PCP elevations of CRP are associated with disease severity (PaO(2)) and poor outcome and might be used prognostically, together with other mortality risk factors; further prospective evaluation is needed.

Malignant mesothelioma (MM) remains a highly deadly malignancy with poor treatment option. The MM cells further promote a highly inflammatory microenvironment, which contributes to tumor initiation, development, severity and propagation. We reasoned that the anti-inflammatory actions of mesenchymal stromal cells (MSCs) and further antitumor effects of MSCs engineered to overexpress tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein (MSC-TRAIL) would effectively inhibit mesothelioma growth. Using a mouse xenograft model of intraperitoneal human mesothelioma, native mouse (mMSCs) or human (hMSC) MSCs were administered either systemically (intravenously or intraperitoneally) at various times following tumor inoculation. Both mMSCs and hMSCs localized at the sites of MM tumor growth in vivo and decreased local inflammation. Further, a trend towards decrease in tumor burden was observed. Parallel studies of in vitro exposure of nine primary human mesothelioma cell lines to mMSCs or hMSCs demonstrated reduced tumor cell migration. MSC-TRAIL exposure induced apoptosis of TRAIL-sensitive MM cells in vitro, and both mouse and human MSC-TRAIL significantly reduced the inflammatory tumor environment in vivo. Moreover, human MSC-TRAIL administration significantly reduced peritoneal tumor burden in vivo and increased tumor cell apoptosis. These proof-of-concept studies suggest that TRAIL-expressing MSCs may be useful against malignant mesothelioma.