Ex-vivo expansion of disseminated cancer cells is associated with progression of the disease in patients

Lung cancer is one of the most common tumor diseases in Europe and the most common cause of cancer-related deaths worldwide. There appears to be a correlation between the occurrence of disseminated cancer cells (DCCs) in the lymph nodes or bone marrow, the functional and molecular properties of these cells, and later incidences of metastasis. The presence of these epithelial cells can be detected primarily by means of the markers cytokeratin or EpCAM (epithelial cell adhesion molecule). Ex-vivo expansion of these cells has yet to be adequately investigated and so far, it has not been studied in the context of increased metastasis. To detect the cells that metastasis originates from and to gain a better understanding of the cellular basis of metastasis, researchers in a recent study used a cultivation method that does not rely on markers, focusing instead on sphere formation and characterization (Treitschke, S. et al., 2023: DOI 10.1002/ijc.34658).

A total of 131 lung cancer patients were recruited for this study, in collaboration with the University Hospital Regensburg and the hospital Krankenhaus Barmherzige Brüder Regensburg. The scientists took 199 lymph node biopsies and used them to generate cell suspensions, which were then analyzed using different methods in parallel. In one of these methods, immunocytological quantification was used to test the cell suspensions for the presence of EpCAM-positive DCCs, while in another, the specimens were cultivated in non-adherent, serum-free sphere cell culture conditions for a period of weeks. Sphere formation was observed in 35 percent of all the cultures in the study (69/199). The spheres formed in ex-vivo conditions and their cellular composition were then characterized using a wide range of analysis methods from molecular biology, such as gene expression signatures, the detection of typical lung cancer mutations and the identification of genome aberrations. Interestingly, a correlation was shown between sphere formation and the detection of DCCs, along with significantly poorer prognoses for patient survival. In addition, the researchers showed that the prognostic impact of sphere formation was strongly associated with high numbers of EpCAM-positive DCCs and aberrant genotypes in the expanded spheres. While there were some individual cases where sphere formation was observed in patients that showed no signs of cell dissemination in their lymph nodes, these spheres only showed infrequent expression of signature genes and did not exhibit typical lung cancer mutations or copy number variations. However, they may be linked to disease progression more than five years after curative surgery.

In conclusion, the study showed that ex-vivo expansion of DCCs from the lymph nodes of lung cancer patients could be used to identify cells that are associated with the progression of metastasis.