Biophysical studies of cancer cells' traverse-vessel behaviors under different pressures revealed cells' motion state transition

Significance of circulating tumor cells in lung cancer: a narrative review

Background and Objective

In cancer patients, circulating tumor cells (CTCs) are employed as "Liquid Biopsy" for tumor detection, prognosis and assessment of the response to therapy. CTCs are responsible for tumor dissemination but the mechanisms involved in intravasation, survival in the circulation and extravasation at secondary sites to establish metastases are not fully characterized. In lung cancer patients, CTCs are present in very high numbers in small cell lung cancer (SCLC) that is found disseminated in most patients upon first presentation and has a dismal prognosis. This review aims at the discussion of recent work on metastatic SCLC and novel insights into the process of dissemination derived from the access to a panel of unique SCLC CTC lines.

Methods

PubMed and Euro PMC were searched from January 1st, 2015 to September 23th, 2022 using the following key words: "SCLC", "NSCLC", "CTC" and "Angiogenesis" and supplemented by data from our own work.

Key Content and Findings

Experimental and clinical data indicate that the intravasation of single, apoptotic or clustered CTCs occur via leaky neoangiogenetic vessels in the tumor core and not via crossing of the adjacent tumor stroma after EMT. Furthermore, in lung cancer only EpCAM-positive CTCs have been found to have prognostic impact. All our established SCLC CTC lines form spontaneously EpCAM-positive large and chemoresistant spheroids (tumorospheres) that may become trapped in microvessels in vivo and are suggested to extravasate by physical force. The rate-limiting step of the shedding of CTCs is most likely the presence of irregular and leaky tumor vessels or in case of SCLC, also via vessels formed by vasculogenic mimicry. Therefore, lower microvessel densities (MVD) in NSCLC can explain the relative rarity of CTCs in NSCLC versus SCLC.

Conclusions

The detection of CTCs lacks standardized techniques, is difficult in non-metastatic patients and important cell biological mechanisms of dissemination need still to be resolved, especially in respect to the actual metastasis-inducing cells. Expression of VEGF and the MVD are key prognostic indicators for tumors and ultimately, enumeration of CTCs seems to reflect neoangiogenetic vascular supply of tumors and prognosis.

Pneumatic Cell Stretching Chip to Generate Uniaxial Strain Using an Elastomeric Membrane with Ridge Structure

Cyclic mechanical stretching, including uniaxial strain, has been manifested to regulate the cell morphology and functions directly. In recent years, many techniques have been developed to apply cyclic mechanical stretching to cells in vitro. Pneumatically actuated stretching is one of the extensively used methods owing to its advantages of integration, miniaturization, and long-term stretching. However, the intrinsic difficulty in fabrication and adjusting the strain mode also impedes its development and application. In this study, inspired by the topological defects principle, we incorporated a ridge structure into the membrane surface of a traditional pneumatic cavity stretching chip to regulate the strain mode. Our results showed that the surface ridge structure can directly change the equiaxial stretching mode to the standard uniaxial strain, and it is ridge width-independent. The uniaxial strain mode was further proved by the cell orientation behavior under cyclic stretching stimulation. Moreover, it is easy to realize the multimodal strain fields by controlling the width and height of the ridge and to achieve high-throughput testing by creating a cavity array using microfabrication. Together, we propose a smart method to change the surface strain field and introduce a simple, yet effective, high-throughput pneumatically actuated uniaxial stretching platform, which can not only realize the multimodal mechanical stimulation but also achieve multiscale mechanosensing behaviors of single-cell or multi-cell (tissue and/or organoid) mechanobiology applications.