Beyond talc pleurodesis: do we really need new methods?

Single-cell RNA sequencing captures patient-level heterogeneity and associated molecular phenotypes in breast cancer pleural effusions

BACKGROUND

Malignant pleural effusions (MPEs) are a common complication of advanced cancers, particularly those adjacent to the pleura, such as lung and breast cancer. The pathophysiology of MPE formation remains poorly understood, and although MPEs are routinely used for the diagnosis of breast cancer patients, their composition and biology are poorly understood. It is difficult to distinguish invading malignant cells from resident mesothelial cells and to identify the directionality of interactions between these populations in the pleura. There is a need to characterize the phenotypic diversity of breast cancer cell populations in the pleural microenvironment, and investigate how this varies across patients.

METHODS

Here, we used single-cell RNA-sequencing to study the heterogeneity of 10 MPEs from seven metastatic breast cancer patients, including three Miltenyi-enriched samples using a negative selection approach. This dataset of almost 65 000 cells was analysed using integrative approaches to compare heterogeneous cell populations and phenotypes.

RESULTS

We identified substantial inter-patient heterogeneity in the composition of cell types (including malignant, mesothelial and immune cell populations), in expression of subtype-specific gene signatures and in copy number aberration patterns, that captured variability across breast cancer cell populations. Within individual MPEs, we distinguished mesothelial cell populations from malignant cells using key markers, the presence of breast cancer subtype expression patterns and copy number aberration patterns. We also identified pleural mesothelial cells expressing a cancer-associated fibroblast-like transcriptomic program that may support cancer growth.

CONCLUSIONS

Our dataset presents the first unbiased assessment of breast cancer-associated MPEs at a single cell resolution, providing the community with a valuable resource for the study of MPEs. Our work highlights the molecular and cellular diversity captured in MPEs and motivates the potential use of these clinically relevant biopsies in the development of targeted therapeutics for patients with advanced breast cancer.

A study of efficacy and safety of tranexamic acid versus iodopovidone in pleurodesis via pigtail catheter in management of recurrent pleural effusion

Background

Researches to detect the ideal agent for pleurodesis are still continuous; iodopovidone is one of the best agents for pleurodesis that are commonly used. Tranexamic acid is also considered by many authors as a safe, cheap, and effective agent for pleurodesis.

Results

Group I (patients subjected to pleurodesis using tranexamic acid) had a higher complete response with a success rate 88% compared with 76% for group II (patients subjected to pleurodesis using iodopovidone) at the end of the study in 12 weeks. Complications were nearly equal in both groups. Chest pain, hypotension, and fever were the most common reported complications.

Conclusions

Tranexamic acid and iodopovidone were found to be effective alternative agents for pleurodesis with low cost and minimal complications.

Efficacy of mistletoe for chemical pleurodesis in rats without malignancy

Chemical pleurodesis is an effective treatment modality to reduce recurrence of malignant effusion. Several agents have been used in chemical pleurodesis but, it is not yet clear which is better. Eighteen Sprague-Dawley rats were used and classified into three groups: a group intrapleurally injected normal saline (group A, n=6), 400mg/kg talc (group B, n=6), and 9mg/kg mistletoe extraction (ME) (group C, n=6). Autopsy was performed to evaluate the pleural adhesion, pathologic examination of pleura and lung and bronchoalveolar lavage fluid analysis 4 weeks after pleurodesis. Both group B and C showed an obvious pleural adhesion and there was no significant difference in grade of pleural adhesion between two groups (p=0.58). The parietal pleural thickness in talc group than ME group was significantly thicker (p=0.002) and the visceral pleura of talc group showed marked foreign body reaction with fibrosis and many multinucleated giant cells associated with talc crystal. This study suggests that pleurodesis using ME in condition without malignancy has comparable effect to pleurodesis using talc. However, additional experimental study in large animal or clinical trials would be required to prove a safety and an efficacy of pleurodesis using ME.

The effect of silver nitrate pleurodesis after a failed thoracoscopic talc poudrage

Background. Chemical pleurodesis is the procedure of choice in the management of recurrent malignant pleural effusions (MPE). Talc is probably the most effective sclerosant, with a success rate of 80%. The aim of this study is to demonstrate the effectiveness of silver nitrate solution (SNS) pleurodesis after an unsuccessful thoracoscopic talc poudrage. Methods. Between 2011 and 2013 one hundred and nine patients with unilateral MPE underwent thoracoscopic talc poudrage. Seventeen patients who did not obtain a successful pleurodesis via thoracoscopic procedure were considered for an SNS slurry. The pleural injectate consisted of 100 mL 1% SNS with 10 mL of lidocaine (100 mg/5 mL). The SNS procedure was undertaken once and repeated with the same dose in 5 patients. Results. The duration of follow-up period was 30 days. Subjective pain was low and the same before and after SNS procedure (P value = NS). The mean daily fluid drainage was statistically different (P = 0.001) comparing values before (597.0 ± 122.8 mL) and after SNS procedure (109.1 ± 22.3 mL). After 30 days from SNS procedure recurrence of pleural effusion was observed in 2 patients (11%). Conclusions. The present study demonstrates that SNS is an effective agent for producing pleurodesis after a failed thoracoscopic talc poudrage.

Beneficial impact of CCL2 and CCL12 neutralization on experimental malignant pleural effusion

Using genetic interventions, we previously determined that C-C motif chemokine ligand 2 (CCL2) promotes malignant pleural effusion (MPE) formation in mice. Here we conducted preclinical studies aimed at assessing the specific therapeutic potential of antibody-mediated CCL2 blockade against MPE. For this, murine MPEs or skin tumors were generated in C57BL/6 mice by intrapleural or subcutaneous delivery of lung (LLC) or colon (MC38) adenocarcinoma cells. Human lung adenocarcinoma cells (A549) were used to induce MPEs in severe combined immunodeficient mice. Intraperitoneal antibodies neutralizing mouse CCL2 and/or CCL12, a murine CCL2 ortholog, were administered at 10 or 50 mg/kg every three days. We found that high doses of CCL2/12 neutralizing antibody treatment (50 mg/kg) were required to limit MPE formation by LLC cells. CCL2 and CCL12 blockade were equally potent inhibitors of MPE development by LLC cells. Combined CCL2 and CCL12 neutralization was also effective against MC38-induced MPE and prolonged the survival of mice in both syngeneic models. Mouse-specific CCL2-blockade limited A549-caused xenogeneic MPE, indicating that host-derived CCL2 also contributes to MPE precipitation in mice. The impact of CCL2/12 antagonism was associated with inhibition of immune and vascular MPE-related phenomena, such as inflammation, new blood vessel assembly and plasma extravasation into the pleural space. We conclude that CCL2 and CCL12 blockade are effective against experimental MPE induced by murine and human adenocarcinoma in mice. These results suggest that CCL2-targeted therapies may hold promise for future use against human MPE.

Malignant pleural effusion: tumor-host interactions unleashed

Malignant pleural effusion (MPE) poses a significant clinical problem. Current nonetiologic management is suboptimal in terms of efficacy and safety. In light of recent research progress, we propose herein a new view of MPE development, which may rapidly translate into meaningful changes in therapeutics. In addition to tumor-induced impairment of pleural fluid drainage, pertinent findings point toward another pathway to MPE formation: a vicious loop of interactions between pleural-based tumor cells and the host vasculature and immune system that results in increased net fluid production via enhanced plasma extravasation into the pleural space. The ability of tumor cells to trigger this cascade likely rests on a specific and distinct transcriptional repertoire, which results in important vasoactive events in the pleural space. Although the characterization of tumor-derived factors responsible for MPE development is in the making, an additional, indirect path to MPE was recently demonstrated: tumor cells recruit and co-opt host cells and mediators, which, in turn, amplify tumor cell-primed fluid leakage and impact tumor cell functions. Importantly, recent evidence suggests that the biologic events that culminate in clinical MPE are likely amenable to therapeutic inhibition and even prevention. In this perspective, the scientific basis for an update of current concepts of MPE formation is highlighted. Key questions for future research are posed. Finally, a vision for novel, effective, safe, and convenient treatment modalities that can be offered to outpatients with MPE is set forth.

Secreted phosphoprotein-1 directly provokes vascular leakage to foster malignant pleural effusion

Secreted phosphoprotein-1 (SPP1) promotes cancer cell survival and regulates tumor-associated angiogenesis and inflammation, both central to the pathogenesis of malignant pleural effusion (MPE). Here, we examined the impact of tumor- and host-derived SPP1 in MPE formation and explored the mechanisms by which the cytokine exerts its effects. We used a syngeneic murine model of lung adenocarcinoma-induced MPE. To dissect the effects of tumor- versus host-derived SPP1, we intrapleurally injected wild-type and SPP1-knockout C57/BL/6 mice with either wild-type or SPP1-deficient syngeneic lung cancer cells. We demonstrated that both tumor- and host-derived SPP1 promoted pleural fluid accumulation and tumor dissemination in a synergistic manner (P<0.001). SPP1 of host origin elicited macrophage recruitment into the cancer-affected pleural cavity and boosted tumor angiogenesis, whereas tumor-derived SPP1 curtailed cancer cell apoptosis in vivo. Moreover, the cytokine directly promoted vascular hyper-permeability independently of vascular endothelial growth factor. In addition, SPP1 of tumor and host origin differentially affected the expression of proinflammatory and angiogenic mediators in the tumor microenvironment. These results suggest that SPP1 of tumor and host origin impact distinct aspects of MPE pathobiology to synergistically promote pleural fluid formation and pleural tumor progression. SPP1 may present an attractive target of therapeutic interventions for patients with MPE.