Combined targeting of endothelin A receptor and epidermal growth factor receptor in ovarian cancer shows enhanced antitumor activity

Epidermal growth factor-induced enhancement of glioblastoma cell migration in 3D arises from an intrinsic increase in speed but an extrinsic matrix- and proteolysis-dependent increase in persistence

Epidermal growth factor (EGF) receptor-mediated cell migration plays a vital role in invasion of many tumor types. EGF receptor ligands increase invasiveness in vivo, but it remains unclear how consequent effects on intrinsic cell motility behavior versus effects on extrinsic matrix properties integrate to result in net increase of translational speed and/or directional persistence of migration in a 3D environment. Understanding this convolution is important for therapeutic targeting of tumor invasion, as key regulatory pathways for intrinsic versus extrinsic effects may not be coincident. Accordingly, we have undertaken a quantitative single-cell imaging study of glioblastoma cell movement in 3D matrices and on 2D substrata across a range of collagen densities with systematic variation of protease-mediated matrix degradation. In 3D, EGF induced a mild increase in cell speed and a strong increase in directional persistence, the latter depending heavily on matrix density and EGF-stimulated protease activity. In contrast, in 2D, EGF induced a similarly mild increase in speed but conversely a decrease in directional persistence (both independent of protease activity). Thus, the EGF-enhanced 3D tumor cell migration results only partially from cell-intrinsic effects, with override of cell-intrinsic persistence decrease by protease-mediated cell-extrinsic reduction of matrix steric hindrance.

Integrin alphavbeta3 mediates upregulation of epidermal growth-factor receptor expression and activity in human ovarian cancer cells

Upon overexpression of integrin alphavbeta3 and its engagement by vitronectin, we previously showed enhanced adhesion, proliferation, and motility of human ovarian cancer cells. By studying differential expression of genes possibly related to these tumor biological events, we identified the epidermal growth-factor receptor (EGF-R) to be under control of alphavbeta3 expression levels. Thus in the present study we characterized alphavbeta3-dependent changes of EGF-R and found significant upregulation of its expression and activity which was reflected by prominent changes of EGF-R promoter activity. Upon disruption of DNA-binding motifs for the transcription factors p53, ETF, the repressor ETR, p50, and c-rel, respectively, we sought to identify DNA elements contributing to alphavbeta3-mediated EGF-R promoter induction. Both, the p53- and ETF-mutant, while exhibiting considerably lower EGF-R promoter activity than the wild type promoter, retained inducibility by alphavbeta3. Mutation of the repressor motif ETR, as expected, enhanced EGF-R promoter activity with a further moderate increase upon alphavbeta3 elevation. The p50-mutant displayed EGF-R promoter activity almost comparable to that of the wild type promoter with no impairment of induction by alphavbeta3. However, the activity of an EGF-R promoter mutant displaying a disrupted c-rel-binding motif did not only prominently decline, but, moreover, was not longer responsive to enhanced alphavbeta3, involving this DNA element in alphavbeta3-dependent EGF-R upregulation. Moreover, alphavbeta3 did not only increase the EGF-R but, moreover, also led to obvious co-clustering on the cancer cell surface. By studying alphavbeta3/EGF-R-effects on the focal adhesion kinase (FAK) and the mitogen activated protein kinases (MAPK) p44/42 (erk(-1)/erk(-2)), having important functions in synergistic crosstalk between integrins and growth-factor receptors, we found for both significant enhancement of expression and activity upon alphavbeta3/VN interaction and cell stimulation by EGF. Upregulation of the EGF-R by integrin alphavbeta3, both receptor molecules with a well-defined role as targets for cancer treatment, might represent an additional mechanism to adapt synergistic receptor signaling and crosstalk in response to an altered tumor cell microenvironment during ovarian cancer progression.

Akt1 is necessary for the vascular maturation and angiogenesis during cutaneous wound healing

Previous in vivo and in vitro studies have shown that Akt1 serves as a crucial regulator of vascular maturation, extracellular matrix composition, and angiogenesis in tumors. Hence, we hypothesized that Akt1 may be necessary for other angiogenesis-dependent processes, including wound healing. Using Akt1 (-/-) and Akt2 (-/-) mice, we demonstrate that deficiency of Akt1, but not Akt2, results in impaired assembly of collagen in skin wounds and around the blood vessels. Wounds in Akt1 (-/-) mice, but not in Akt2 (-/-) mice, were characterized by reduced vascular area as well as impaired vascular maturation as evidenced by reduced smooth muscle cell recruitment. Expression level of a major angiogenic growth factor, VEGF, was significantly lower in wound tissues of Akt1 (-/-) mice as compared to WT. However, despite the impaired collagen assembly and reduced angiogenesis in Akt1 (-/-) wounds, no significant difference in migration of fibroblasts into the wound area was observed between WT and Akt1 (-/-) mice. Importantly, the dynamics of wound closure were similar between WT, Akt1 (-/-), and Akt2 (-/-) mice. Thus, it appears that although the lack of Akt1 impairs VEGF expression, wound angiogenesis, and subsequent maturation of vasculature, it has no effect on the wound closure. These findings may have clinical applications for the improvement of treatment procedures with reported history of wound healing complications.

Endothelin-1 enhances proliferation of lung cancer cells by increasing intracellular free Ca2+

Endothelin-1 (ET-1), the most potent vasoconstrictor, has been shown to be mitogenic in many tumor cells as well as in vascular cells. It was previously reported that the mRNA of ET-1 and endothelin receptors (ETRs) are expressed in lung cancer cells. However, their biological role in lung cancer remains to be explored. The purpose of this study was to determine whether ET-1 stimulates proliferation of the human lung adenocarcinoma cell SPC-A1 and probe its cellular mechanism. Reverse-transcription polymerase chain reaction and Western blot analysis showed that both the mRNA and protein of ET-1, ET A R and ET B R are expressed in SPC-A1 cells. Application of ET-1 at 10(-15)-10(-8) M caused a dose-dependent cell proliferation and an increase in intracellular free Ca2+ concentration ([Ca2+]i). This ET-1-induced cell proliferation and [Ca2+]i increase were completely abolished by BQ123, a selective ET A R antagonist, but not by BQ788, a selective ET B R antagonist. Furthermore, it was significantly reduced by U73122, a specific inhibitor of phospholipase C (PLC), but not by U73433, the structural isomer of U73122. Chelating extracellular Ca2+ or blocking voltage dependent calcium channels by nifedipine also significantly reduced the mitogenic effect of ET-1 and [Ca2+]i increase in SPC-A1 cells. These results indicate that ET-1 acts as an autocrine growth factor and enhances proliferation of SPC-A1 cells via activation of ET A R. The phosphoinositol/Ca2+ pathway and Ca2+ influx through voltage dependent Ca2+ channels activated by ET A R contribute to this process.