Purpose: Circulating tumor cells (CTCs) can provide a potentially minimal invasive source for monitoring chemotherapeutic effects. However, detailed in vivo dynamics of CTC after chemotherapy remain largely unknown.
Methods: We monitored CTC number and morphology early after chemotherapy using a newly developed cytology-based CTC detection device and triple-negative breast cancer mouse CTC models with spontaneous lung metastatic potential.
Results: Paclitaxel inhibited cell growth of breast cancer cells by mainly G2/M cell cycle arrest and partly apoptosis, whereas doxorubicin inhibited cell growth mainly by apoptosis and partly G2 cell cycle arrest in vitro. The number of CTCs was significantly increased 3-10 days after paclitaxel and doxorubicin chemotherapy and decreased thereafter in two mouse CTC models. The transiently increased CTCs early post-chemotherapy consisted of not only G2/M arrested cells (apoptotic cells), but also morphologically near-intact live cells. This heterogeneous cell population of CTCs was similar to that of primary tumor tissue after chemotherapy.
Conclusions: These results indicate that CTCs can be mobilized from the primary tumor in rapid response to chemotherapy and suggest the possibility that CTC monitoring from both numerical and morphological viewpoints early after chemotherapy using a cytology-based CTC detection device would be a useful diagnostic tool for predicting drug sensitivity/resistance in preclinical and clinical setting.
Keywords: Breast cancer; CTC; Chemotherapy; Cytology; In vivo dynamics; Preclinical study.