Malignant Pleural Mesothelioma (MPM) is typically diagnosed 20-50 years after exposure to asbestos and evolves along an unknown evolutionary trajectory. To elucidate this path, we conducted ...multi-regional exome sequencing of 90 tumour samples from 22 MPMs acquired at surgery. Here we show that exomic intratumour heterogeneity varies widely across the cohort. Phylogenetic tree topology ranges from linear to highly branched, reflecting a steep gradient of genomic instability. Using transfer learning, we detect repeated evolution, resolving 5 clusters that are prognostic, with temporally ordered clonal drivers. BAP1/-3p21 and FBXW7/-chr4 events are always early clonal. In contrast, NF2/-22q events, leading to Hippo pathway inactivation are predominantly late clonal, positively selected, and when subclonal, exhibit parallel evolution indicating an evolutionary constraint. Very late somatic alteration of NF2/22q occurred in one patient 12 years after surgery. Clonal architecture and evolutionary clusters dictate MPM inflammation and immune evasion. These results reveal potentially drugable evolutionary bottlenecking in MPM, and an impact of clonal architecture on shaping the immune landscape, with potential to dictate the clinical response to immune checkpoint inhibition.
OBJECTIVES
For many years, extrapleural pneumonectomy (EPP) was the operation of choice for the radical management of pleural mesothelioma in the UK. However, doubts surrounding the efficacy of EPP, ...and the change in demographics of the affected population, have prompted a transition in our practice towards extended pleurectomy/decortication (EPD). The aim of this study was to determine the effects an intentional transition from EPP to EPD has had on patient outcome.
METHODS
Data from 362 patients undergoing radical surgery (229 EPD, 133 EPP) during 1999–2014 were included. Demographics and outcome were compared between the two groups; EPP versus EPD.
RESULTS
The median age of patients undergoing EPD was significantly higher than those undergoing EPP 57 years (range 14–70 years) vs 65 years (range 42–81 years), P < 0.001. There was a significantly higher proportion of patients with performance status ≥1 in the EPD group (46.3 vs 35.4%, P = 0.047). There was no difference in the median length of hospital stay between the two groups 14 days (range 1–133 days) vs 13 days (range 0–93 days), P = 0.409. There was also no difference between the groups in terms of in-hospital mortality (EPP 5.3% and EPD 6.6%, P = 0.389), 30-day mortality EPP 8 (6.0%) and EPD 8 (3.5%), P = 0.294 or 90-day mortality EPP 18 (13.5%) and EPD 21 (9.2%), P = 0.220. There was a significantly higher early reoperation rate in the EPP group (15.0 vs 6.2%, P = 0.008) but a significantly higher late reoperation rate in the EPD group (0.8 vs 5.3%, P = 0.037). There was no significant difference in overall survival or disease-free interval between the two groups (P = 0.899 and P = 0.399, respectively). However, overall survival was significantly greater in patients over the age of 65 undergoing EPD (12.5 vs 4.7 months, P = 0.001).
CONCLUSION
The transition from EPP to EPD in our standard practice has enabled us to operate on more elderly, frail patients with no significant increase in use of hospital resources, and without detriment to overall survival.
We hypothesized that small molecule transcriptional perturbation could be harnessed to target a cellular dependency involving protein arginine methyltransferase 5 (PRMT5) in the context of ...methylthioadenosine phosphorylase (MTAP) deletion, seen frequently in malignant pleural mesothelioma (MPM). Here we show, that MTAP deletion is negatively prognostic in MPM. In vitro, the off-patent antibiotic Quinacrine efficiently suppressed PRMT5 transcription, causing chromatin remodelling with reduced global histone H4 symmetrical demethylation. Quinacrine phenocopied PRMT5 RNA interference and small molecule PRMT5 inhibition, reducing clonogenicity in an MTAP-dependent manner. This activity required a functional PRMT5 methyltransferase as MTAP negative cells were rescued by exogenous wild type PRMT5, but not a PRMT5E444Q methyltransferase-dead mutant. We identified c-jun as an essential PRMT5 transcription factor and a probable target for Quinacrine. Our results therefore suggest that small molecule-based transcriptional perturbation of PRMT5 can leverage a mutation-selective vulnerability, that is therapeutically tractable, and has relevance to 9p21 deleted cancers including MPM.
Malignant mesothelioma is an aggressive tumour of the pleura (MPM) or peritoneum with a clinical presentation at an advanced stage of the disease. Current therapies only marginally improve survival ...and there is an urgent need to identify new treatments. Carcinoma-associated fibroblasts (CAFs) represent the main component of a vast stroma within MPM and play an important role in the tumour microenvironment. The influence of CAFs on cancer progression, aggressiveness and metastasis is well understood; however, the role of CAF-derived extracellular vesicles (CAF-EVs) in the promotion of tumour development and invasiveness is underexplored. We purified CAF-EVs from MPM-associated cells and healthy dermal human fibroblasts and examined their effect on cell proliferation and motility. The data show that exposure of healthy mesothelial cells to EVs derived from CAFs, but not from normal dermal human fibroblasts (NDHF) resulted in activating pro-oncogenic signalling pathways and increased proliferation and motility. Consistent with its role in suppressing Yes-Associated Protein (YAP) activation (which in MPM is a result of Hippo pathway inactivation), treatment with Simvastatin ameliorated the pro-oncogenic effects instigated by CAF-EVs by mechanisms involving both a reduction in EV number and changes in EV cargo. Collectively, these data determine the significance of CAF-derived EVs in mesothelioma development and progression and suggest new targets in cancer therapy.
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
loss-of-function mutations, which are frequent in MM, as a potential genomic stratification tool for TRAIL sensitivity with immediate and actionable therapeutic implications.
Malignant pleural mesothelioma (MPM) has a poor overall survival with few treatment options. Whole genome sequencing (WGS) combined with the immune features of MPM offers the prospect of identifying ...changes that could inform future clinical trials.
We analysed somatic mutations from 229 MPM samples, including previously published data and 58 samples that had undergone WGS within this study. This was combined with RNA-seq analysis to characterize the tumour immune environment.
The comprehensive genome analysis identified 12 driver genes, including new candidate genes. Whole genome doubling was a frequent event that correlated with shorter survival. Mutational signature analysis revealed SBS5/40 were dominant in 93% of samples, and defects in homologous recombination repair were infrequent in our cohort. The tumour immune environment contained high M2 macrophage infiltrate linked with MMP2, MMP14, TGFB1 and CCL2 expression, representing an immune suppressive environment. The expression of TGFB1 was associated with overall survival. A small subset of samples (less than 10%) had a higher proportion of CD8 T cells and a high cytolytic score, suggesting a 'hot' immune environment independent of the somatic mutations.
We propose accounting for genomic and immune microenvironment status may influence therapeutic planning in the future.
OBJECTIVES
Macroscopic complete resection with lung preservation is the objective of radical management of pleural mesothelioma (MPM). Total removal of visceral and parietal pleura ...(pleurectomy/decortication) almost invariably proceeds to an extended pleurectomy/decortication (EPD) to ensure macroscopic complete resection. We suspected this may not always be necessary.
METHODS
We reviewed 314 patients, 86.0% male, median age 62 years (range 14–81 years) undergoing radical surgery for MPM from 1999 to 2014, by either EPD or extrapleural pneumonectomy. The extent of diaphragmatic muscle involvement was recorded from postoperative pathology. Patients were divided into three groups: no involvement, non-transmural, transmural diaphragmatic invasion.
RESULTS
A total of 213 (68%) patients underwent EPD, 237 (75.5%) had epithelioid disease and 57.6% were node positive. There was no difference between the three groups in terms of age, cell type, laterality, neoadjuvant chemotherapy and operation. There was a higher degree of diaphragm involvement in females (P = 0.01) and in patients with positive lymph nodes (P = 0.01). No evidence of diaphragmatic involvement was found following pathological assessment of the resection specimen in 119 patients (37.9%). The incidence of abdominal disease progression was 23.9%. There was no correlation with degree of diaphragmatic invasion (ρ = 0.01 P = 0.88). Overall survival of those with abdominal progression was similar to those with progression elsewhere: 14.5 vs 13.0 months (P = 0.79), and with those with no progression (16.7 months, P = 0.189). There was no difference in survival when stratified by diaphragmatic involvement (P = 0.44).
CONCLUSIONS
In our cohort, there was no evidence of diaphragmatic invasion in over 30% of patients, and we have also failed to find evidence that peritoneal disease progression affects overall survival following radical management. It may therefore theoretically be unnecessary to resect the diaphragm in all cases, and a pleurectomy–decortication could suffice. However, there is an unknown risk of R2 resection which would prejudice survival, and as such we would advocate resecting the diaphragm in all cases to avoid an R2 resection.
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