G protein‑mediated EGFR transactivation is a common mechanism through which the CXCL12 receptors, CXCR4 and CXCR7, control human cancer cell migration

C‑X‑C motif chemokine 12 (CXCL12) promotes metastasis of several tumors by affecting cell migration and invasion via its receptors, C‑X‑C chemokine receptor type (CXCR)4 and CXCR7. Current therapeutic approaches focus on the selective inactivation of either CXCR4 or CXCR7 in patients with cancer. Alternative strategies may emerge from the analysis of downstream events that mediate the migratory effects of CXCL12 in cancer cells. While CXCR4 activates cell signaling through both G proteins and arrestins, CXCR7 is believed to preferentially signal through arrestins. The present study analyzed the CXCL12‑dependent chemotaxis of A549, C33A, DLD‑1, MDA‑MB‑231 and PC‑3 cells, in which either the activity of G proteins, EGFR or Src kinase was inhibited pharmacologically or the expression of arrestins was inhibited by RNA interference. The results demonstrated that CXCL12‑induced migration of A549, C33A, DLD‑1, MDA‑MB‑231 and PC‑3 cells was attenuated by the Gαi/o‑inhibitor pertussis toxin (PTX), but was unaffected by small interfering RNA‑mediated gene silencing of β‑arrestin1/2. In particular, the sensitivity of DLD‑1 migration to PTX was unexpected, as it is solely dependent on the non‑classical chemokine receptor, CXCR7. Furthermore, chemotactic responses to CXCL12 were additionally prevented by inhibiting EGFR activity via AG1478 and Src kinase activity via Src inhibitor‑1. In conclusion, the results of the present study suggest that G protein‑ and Src‑dependent transactivation of EGFR is a common mechanism through which CXCL12‑bound CXCR4 and/or CXCR7 control cancer cell migration and metastasis. These findings highlight EGFR as a potential therapeutic target that interferes with CXCL12‑induced cancer expansion.

Comparative Analysis of Cytotoxic Activity of New Nitrosyl Iron-Sulfur Complexes in Human Tumor Cells In Vitro

We studied cytotoxic activity of new tetranitrosyl NO-generating binuclear iron-sulfur [Fe-S] complexes containing different ligands in the molecule against tumor cells in vitro. Cytotoxic activity of the most active complex with cysteamine (CysAm) was compared with that of antitumor drug cisplatin. Caspase activation and morphological changes in cells were visualized by fluorescence microscopy. Fluorescence of active caspases 3 and 7 and changes in nuclear DNA in cells in the presence of CyAm were detected by using fluorochrome-labeled inhibitor of caspases (FLICA) and Hoechst and propidium iodide reagents. Similar cytotoxic activities of CyAm and cisplatin were demonstrated in various human tumor cell lines of different histogenesis. Therefore, a new class of NO-donating [Fe-S] complexes can provide the base of potential drugs for chemotherapy with a new mechanism of action.

Cytotoxic Effects of Diterpenoid Alkaloids Against Human Cancer Cells

Diterpenoid alkaloids are isolated from plants of the genera Aconitum, Delphinium, and Garrya (Ranunculaceae) and classified according to their chemical structures as C18-, C19- or C20-diterpenoid alkaloids. The extreme toxicity of certain compounds, e.g., aconitine, has prompted a thorough investigation of how structural features affect their bioactivities. Therefore, natural diterpenoid alkaloids and semi-synthetic alkaloid derivatives were evaluated for cytotoxic effects against human tumor cells [A549 (lung carcinoma), DU145 (prostate carcinoma), MDA-MB-231 (triple-negative breast cancer), MCF-7 (estrogen receptor-positive, HER2-negative breast cancer), KB (identical to cervical carcinoma HeLa derived AV-3 cell line), and multidrug-resistant (MDR) subline KB-VIN]. Among the tested alkaloids, C19-diterpenoid (e.g., lipojesaconitine, delcosine and delpheline derivatives) and C20-diterpenoid (e.g., kobusine and pseudokobusine derivatives) alkaloids exhibited significant cytotoxic activity and, thus, provide promising new leads for further development as antitumor agents. Notably, several diterpenoid alkaloids were more potent against MDR subline KB-VIN cells than the parental drug-sensitive KB cells.

Antiproliferative Activity of a New Nitrosyl Iron Complex with Cysteamine in Human Tumor Cells In Vitro

We studied cytotoxic activity of a new NO-releasing tetranitrosyl binuclear iron complex with cysteamine (CysAm) for human tumor cells, the relationship between the expression of O6-methylguanine-DNA methyltransferase (MGMT) and cell sensitivity to CysAm, and apoptosis-inducing capacity of this preparation. It was found that histogenetically different cell lines are characterized by different sensitivity to CysAm, and this parameter correlated with the basal level of MGMT. CysAm induced apoptosis via activation of caspases 3 and 7. These data suggest that CysAm can be considered as a potential antitumor agent, but definitive conclusions can be made after preclinical trials.

Cancer stem cell characteristics of circulating tumor cells

PURPOSE

To review the results from previous studies aiming at the molecular characterization of circulating tumor cells (CTC), to specifically address the role of epithelial-mesenchymal-transition (EMT) and stemness features of CTC in their contribution to tumor progression and to summarize potential interference of CTC with the efficacy of radiotherapy.

CONCLUSIONS

Detection of CTC has been reported for most epithelial tumors and has been associated with an increased risk of local and regional recurrence as well as the development of distant metastases. Given a causal relationship between the presence of CTC and tumor progression at the primary or distant sites, several distinct features have to be postulated for these cells: First, a change from an epithelial to a mesenchymal cell-like phenotype which should alleviate the disconnection of individual tumor cells from tight cell-to-cell junctions within the epithelial cell layer and endow single tumor cells with the capacity to migrate into blood vessels; secondly, the presence of stem-cell properties which contribute to the re-establishment of bulk tumor tissue at the primary or metastatic site upon tumor recurrence or distant progression, respectively. Indeed, EMT and stem-cell features were frequently observed in CTC and the phenotype of CTC was established as a stronger predictor of outcome than sole enumeration of CTC in a defined volume of blood. The exploitation of CTC above their use as prognostic marker is still a subject of many ongoing investigations as are the identification of suitable therapeutic targets for this small cell subpopulation.

Dipyridamole combined with tumor necrosis factor-alpha enhances inhibition of proliferation in human tumor cell lines

In the search for cytokines whose antiproliferative action could be enhanced by combination with dipyridamole, 2,6-bis(diethanolamino)-4,8-dipiperidinopyrimido[5,4-d]pyrim idine, the combination of tumor necrosis factor-alpha (TNF-alpha) with this agent was evaluated in various human tumor cell lines. Inhibition of the proliferation of human melanoma cell lines MM-1CB and HMV-1 by TNF-alpha (1-10(2) U/ml) was enhanced in culture dishes by combination treatment with dipyridamole (0.1-10 microM). The enhancement effect was also detected in other tumor cell lines: T98 (glioma), SCC-1CB (squamous cell carcinoma), HAC-2 (ovarian clear-cell carcinoma), HLE (hepatoma), HEC-1 (endometrial adenocarcinoma) and HOC-21 (ovarian serous cystadenocarcinoma). The incorporation of [14C]amino acids and [3H]uridine into acid-insoluble cell materials in the combination-treated cells was not significantly different from that in cells treated with TNF-alpha or dipyridamole. However, the incorporation of [3H]thymidine was specifically inhibited in all cell lines examined after more than 12 h of the TNF-alpha and dipyridamole combination treatment, although neither agent alone inhibited this incorporation. On the other hand, the growth of tumors induced by the injection of MM-1CB and HMV-1 cells into nude mice was more markedly inhibited by the subcutaneous administration of TNF-alpha in combination with orally administered dipyridamole than by either agent alone. The results presented suggested that dipyridamole is beneficial in assuring the effectiveness of anti-cancer cytokine therapy.