Intercellular communication in malignant pleural mesothelioma: properties of tunneling nanotubes

Abstract

Malignant pleural mesothelioma is a particularly aggressive and locally invasive malignancy with a poor prognosis despite advances in understanding of cancer cell biology and development of new therapies. At the cellular level, cultured mesothelioma cells present a mesenchymal appearance and a strong capacity for local cellular invasion. One important but underexplored area of mesothelioma cell biology is intercellular communication. Our group has previously characterized in multiple histological subtypes of mesothelioma a unique cellular protrusion known as tunneling nanotubes (TnTs). TnTs are long, actin filament-based, narrow cytoplasmic extensions that are non-adherent when cultured in vitro and are capable of shuttling cellular cargo between connected cells. Our prior work confirmed the presence of nanotube structures in tumors resected from patients with human mesothelioma. In our current study, we quantified the number of TnTs/cell among various mesothelioma subtypes and normal mesothelial cells using confocal microscopic techniques. We also examined changes in TnT length over time in comparison to cell proliferation. We further examined potential approaches to the in vivo study of TnTs in animal models of cancer. We have developed novel approaches to study TnTs in aggressive solid tumor malignancies and define fundamental characteristics of TnTs in malignant mesothelioma. There is mounting evidence that TnTs play an important role in intercellular communication in mesothelioma and thus merit further investigation of their role in vivo.

Tunneling nanotubes: an alternate route for propagation of the bystander effect following oncolytic viral infection

“…24,37,38 To determine whether mesothelioma cells infected with HSV are capable of transferring virally encoded proteins between cells via TNTs, we infected mesothelioma cells from each cell line separately with NV1066, a mutant HSV strain that encodes the readily-expressed viral enhanced green fluorescence protein (eGFP) transgene. 39–42 After consistent formation of TNTs between malignant mesothelioma cells was observed, NV1066 was added.…”

“…22,24,25,27,38,59 Briefly, these parameters included (i) lack of adherence to the substratum of tissue culture plates, including visualization of TNTs passing over adherent cells; (ii) TNTs connecting two cells or extending from one cell were counted if the width of the extension was estimated to be <1,000 nm; and (iii) a narrow base at the site of extrusion from the plasma membrane. Cellular extensions not clearly consistent with the above parameters were excluded.…”

Intercellular mitochondrial transfer: bioenergetic crosstalk between cells

“…In vitro transfer of mitochondria elicited a chemoresistant phenotype in MCF7 cells. Other investigators show that mitochondrial transfer occurs between cultured human mesothelioma cells (Ady, Desir et al 2014) and human laryngeal squamous carcinoma cells (Antanaviciute, Rysevaite et al 2014). Antanavicuite et al suggest that the mitochondrial transfer might contribute to tumor proliferation.…”

Defining the momiome: Promiscuous information transfer by mobile mitochondria and the mitochondrial genome

“…However, technical limitations in the study of live imaging of mitochondrial transfer through TNTs remains a bottleneck for further characterization of the process in vivo . Recent studies have established a methodology for confocal microscope imaging of TNTs in tumor samples [273, 274]. Technical advancements in intravital confocal imaging would provide further support in identifying the mechanisms of intercellular mitochondrial transfer in and between tumor cells and cells of the tumor microenvironment.…”