Short-Term Ex Vivo Culture of CTCs From Advance Breast Cancer Patients: Clinical Implications

Abstract

Background: Circulating tumor cells (CTC) have relevance as prognostic markers in breast cancer. However, the functional properties of CTCs or their molecular characterization have not been well-studied. Experimental models indicate that only a few cells can survive in the circulation and eventually metastasize. Thus, it is essential to identify these surviving cells capable of forming such metastases. Methods: We isolated viable CTCs from 50 peripheral blood samples obtained from 35 patients with advanced metastatic breast cancer using RosetteSepTM for ex vivo culture. The CTCs were seeded and monitored on plates under low adherence conditions and with media supplemented with growth factors and Nanoemulsions. Phenotypic analysis was performed by immunofluorescence and gene expression analysis using RT-PCR and CTCs counting by Cellsearch® system. Results: We found that in 75% of samples the CTC cultures lasted more than 23 days, predicting a shorter Progression-Free Survival in these patients, independently of having ≥ 5 CTC by Cellsearch®. We also observed that CTCs before and after culture showed a different gene expression profile. Conclusions: the cultivability of CTCs is a predictive factor. Furthermore, the subset of cells capable of growing ex vivo show stem or mesenchymal features and may represent the CTC population with metastatic potential in vivo.

Genome-wide in vivo screen of circulating tumor cells identifies SLIT2 as a regulator of metastasis

“…Our approach however, allowed genome-wide in vivo CRISPR screening to be performed on fresh CTCs directly collected from liquid biopsy without extensive culturing. Avoiding ex vivo culturing of CTCs is important to prevent possible changes in morphology and proliferation of CTC subpopulations 18,19 , which could affect representations of subsets of sgRNAs in the library. Our in vivo CTC CRISPR KO screen elucidated SLIT2 as a secreted factor that promoted the epithelial-to-mesenchymal transition (EMT) of tumor cells, resulting in enhanced intravasation.…”

Genome-wide in vivo screen of circulating tumor cells identifies SLIT2 as a regulator of metastasis

“…Our approach, however, allowed genome-wide in vivo CRISPR screening to be performed on fresh CTCs directly collected from liquid biopsy without extensive culturing. Avoiding ex vivo culturing of CTCs is important to prevent possible changes in morphology and proliferation of CTC subpopulations ( 19 , 20 ), which could affect representations of subsets of sgRNAs in the library. Our in vivo CTC CRISPR KO screen elucidated Slit Guidance Ligand 2 (SLIT2) as a secreted factor that promoted the epithelial-to-mesenchymal transition (EMT) of tumor cells, resulting in enhanced intravasation.…”