BackgroundThe cell microenvironment, especially extracellular matrix proteins, plays an important role in tumor cell response to chemotherapeutic drugs. The present study was designed to investigate whether this microenvironment can influence the antimigratory effect of an anthracycline drug, doxorubicin, when tumor cells are grown in a matrix of type I collagen, a three-dimensional (3D) context which simulates a natural microenvironment.MethodsTo this purpose, we studied the migratory parameters, the integrin expression, and the activation state of focal adhesion kinase (FAK) and GTPase RhoA involved in the formation of focal adhesions and cell movement. These parameters were evaluated at non toxic concentrations which did not affect HT1080 cell proliferation.ResultsWe show that while doxorubicin decreased cell migration properties by 70% in conventional two-dimensional (2D) culture, this effect was completely abolished in a 3D one. Regarding the impact of doxorubicin on the focal adhesion complexes, unlike in 2D systems, the data indicated that the drug neither affected β1 integrin expression nor the state of phosphorylation of FAK and RhoA.ConclusionThis study suggests the lack of antiinvasive effect of doxorubicin in a 3D environment which is generally considered to better mimic the phenotypic behaviour of cells in vivo. Consistent with the previously shown resistance to the cytotoxic effect in a 3D context, our results highlight the importance of the matrix configuration on the tumor cell response to antiinvasive drugs.

In solid tumors, the cell microenvironment appears to be a key determinant in the emergence of drug resistance, a major obstacle to the successful use of antitumor drugs. Our aim was to determine whether type I collagen and fibronectin, proteins of the extracellular matrix, were able to influence the antimigratory properties induced by the antitumor drug doxorubicin. These properties were investigated at doxorubicin concentrations of 10 and 20 nM, which do not affect cell proliferation on a 24 h drug exposure. Using videomicroscopy, we found that these subtoxic doses of doxorubicin were sufficient to inhibit individual tumor cell motion on two-dimensional plastic surfaces. Such a drug treatment induced a dramatic disturbance of actin stress fiber formation and of vinculin distribution in 80% of cells. In contrast, on extracellular matrix proteins, cell speed was unaffected by drug and perturbation of both actin network and vinculin distribution was detected in only 50% of cells, suggesting a protective effect of the microenvironment. In addition, the phosphorylation of focal adhesion kinase and GTPase RhoA was less affected by doxorubicin with cells cultured on extracellular matrix proteins. In conclusion, our findings indicate that the cell microenvironment prevents drug-dependent inhibition of cell migration in vitro. A n increasing body of evidence indicates that the tumor cell microenvironment is a key determinant of cell response to cytotoxic drugs. The environmental causes that contribute to cancer cell survival after initial therapy, allowing resistant cells to proliferate are multifactorial. They include particularly limited drug penetration, tumor cell adaptation to hypoxia, acidic extracellular pH, and direct contact between cancer cells and the ECM or adjacent cells.(1) Concerning ECM proteins, fibronectin or collagen type I and IV have been shown to have the potential to confer resistance to diverse chemotherapeutic agents in cancer cell lines originated from both hematopoietic and solid tumors. (2,3) This has led to the concept of CAM-DR, a form of de novo drug resistance which may play an important role in the acquisition of a multidrug resistance phenotype. (4,5) Studies on the impact of the microenvironment on drug response have focused exclusively on the cytotoxic or proapoptotic effects induced by an extensive panel of well-known chemotherapeutics, either microtubule-disturbing agents such as vinca-alcaloids, taxoids, or DNA-damaging compounds such as nitrogen mustards and anthracyclines. (6,7) However, with chemotherapeutics such as anthracyclines, beyond their well-known antitumor activity, it has been recently demonstrated that they may display potent anti-invasive effects. Indeed, doxorubicin has been shown to inhibit cell escape from multicellular spheroids with cells of prostate, colon, breast, or lung carcinoma.(8) Using the highly mobile fibrosarcoma cell line HT1080 it has been shown that DA-125, a new analog of doxorubicin, inhibits the invasion of these cells by downregulating MMP.(9...

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