Breast cancer angiogenesis: therapy target and prognostic factor

A Comprehensive Review and Perspective on Anticancer Mechanisms of Withaferin A in Breast Cancer

Withaferin A (hereafter abbreviated as WA) is a promising anticancer steroidal lactone abundant in a medicinal plant (Withania somnifera) native to Asia. The root/leaf extract of Withania somnifera, which belongs to the Solanaceae family, continues to be included in the Ayurvedic medicine formulations of alternative medicine practice. Numerous chemicals are detectable in the root/leaf extract of Withania somnifera [e.g., withanolides (WA, withanone, withanolide A, etc.), alkaloids, sitoindosides, etc.], but the anticancer effect of this medicinal plant is largely attributed to WA. Anticancer effect of WA was initially reported in the early 70s in the Ehrlich ascites tumor cell model in vitro Since then, numerous preclinical studies have been performed using cellular and animal models of different cancers including breast cancer to determine cancer therapeutic and chemopreventive effects of WA. Chemoprevention, a word first introduced by Dr. Michael B. Sporn, was intended to impede, arrest, or reverse carcinogenesis at its earliest stages with pharmacologic agents. This review succinctly summarizes the published findings on anticancer pharmacology of WA in breast cancer focusing on pharmacokinetic behavior, in vivo efficacy data in preclinical models in a therapeutic and chemoprevention settings, and its known effects on cancer-relevant cellular processes (e.g., growth arrest, apoptosis induction, autophagy, metabolic adaptation, immune function, etc.) and molecular targets (e.g., suppression of oncogenes such as estrogen receptor-α, STAT3, etc.). Potential gaps in knowledge as well as future research directions essential for clinical development of WA for chemoprevention and/or treatment of breast cancer are also discussed.

Assessment of vascularity in glioblastoma and its implications on patient outcomes

There is little data on why glioblastomas (GBM) hemorrhage and how it may affect patient outcomes. The aim of this study was to investigate the mechanisms of hemorrhage in glioblastoma by examining molecular and genetic features by immunohistochemistry (IHC) and mRNA expression profiles in association with imaging and clinical outcomes. An observational retrospective cohort analysis was performed on 43 FFPE GBM tissue samples. MR images were assessed for the presence of hemorrhage and extent of resection. Specimens were examined for CD34 and CD105 expression using IHC. Tumor mRNA expression profiles were analyzed for 92 genes related to angiogenesis and vascularity. Forty-three specimens were analyzed, and 20 showed signs of hemorrhage, 23 did not. The average OS for patients with GBM with hemorrhage was 19.12 months (95% CI 10.39-27.84), versus 13.85 months (95% CI 8.85-18.85) in those without hemorrhage (p > 0.05). Tumors that hemorrhaged had higher IHC staining for CD34 and CD105. mRNA expression analysis revealed tumor hemorrhage was associated with increased expression of HIF1α and MDK, and decreased expression of F3. Hemorrhage in GBM was not associated with worsened OS. Increased expression of angiogenic factors and increased CD34 and CD105 IHC staining in tumors with hemorrhage suggests that increased hypoxia-induced angiogenesis and vessel density may play a role in glioblastoma hemorrhage. Characterizing tumors that are prone to hemorrhage and mechanisms behind the development of these hemorrhages may provide insights that can lead to the development of targeted, individualized therapies for glioblastoma.

Targeting the tumor blood vessel network to enhance the efficacy of radiation therapy

It has been well established that the vascularization of solid tumors is a prerequisite if a clinically relevant size is to be reached. For progressive tumor growth, the vessel network must continuously expand to satisfy the neoplastic cells' nutritional needs and waste product removal requirements. This utter reliance of the tumor on its vasculature provides a logical target for new approaches to cancer therapy. Indeed, there currently exists a great deal of enthusiasm for the development of interventions that compromise the growth and/or function of the tumor neovasculature. Two primary directions are being pursued. Inhibitors of angiogenesis seek to interrupt the angiogenic process to prevent new vessel formation. Antivascular approaches aim to cause direct damage to the tumor endothelium and thus lead to extensive secondary neoplastic cell death. The application of such strategies as adjuvants to conventional radiation treatments offers unique opportunities to develop more effective cancer therapies.

Targeting tumor blood vessels: an adjuvant strategy for radiation therapy

BACKGROUND AND PURPOSE

The neovascularization of tumor cells is a prerequisite if a clinically relevant tumor size is to be reached. A continuously expanding vessel network supplying nutritional requirements and removing waste products is essential for continued tumor development, growth and survival.

RESULTS

In many tumors, the growing endothelium is unable to fully support the demands of the neoplastic cell population. As a consequence of the inadequacies of the resulting aberrant vasculature, microenvironmental conditions develop in tumors which are not only detrimental to the response of tumors to conventional anticancer treatments, but may lead to or predispose cells to genetic modifications resulting in more aggressive phenotypes and higher metastatic potential. Yet the utter dependence of the tumor on its induced vessel formation for growth, survival and spread has also created a great deal of enthusiasm for developing therapeutic approaches to specifically targeting the tumor microcirculation.

CONCLUSIONS

The application of such strategies as adjuvants to conventional radiation treatments offers unique opportunities to develop more effective cancer therapies.

Angiostatin induces mitotic cell death of proliferating endothelial cells

Angiostatin is an inhibitor of tumor angiogenesis that induces regression of experimental tumors and enhances the antitumor effects of radiation therapy. We report that the cytotoxic effects of angiostatin are restricted to the proliferating endothelial cell population. In addition, angiostatin and ionizing radiation (IR) interact by inducing death of dividing endothelial cells. We also show that angiostatin and IR interact to inhibit endothelial cell migration. These findings demonstrate that angiostatin targets the proliferating tumor vasculature and provide a mechanistic basis for the cytotoxic interaction of angiostatin and IR.

The urokinase-type plasminogen activator system in cancer metastasis: a review

The urokinase-type plasminogen activator (u-PA) system consists of the serine proteinases plasmin and u-PA; the serpin inhibitors alpha2-anti-plasmin, PAI-1 and PAI-2; and the u-PA receptor (u-PAR). Two lines of evidence have strongly suggested an important and apparently causal role for the u-PA system in cancer metastasis: results from experimental model systems with animal tumor metastasis and the finding that high levels of u-PA, PAI-1 and u-PAR in many tumor types predict poor patient prognosis. We discuss here recent observations related to the molecular and cellular mechanisms underlying this role of the u-PA system. Many findings suggest that the system does not support tumor metastasis by the unrestricted enzyme activity of u-PA and plasmin. Rather, pericellular molecular and functional interactions between u-PA, u-PAR, PAI-1, extracellular matrix proteins, integrins, endocytosis receptors and growth factors appear to allow temporal and spatial re-organizations of the system during cell migration and a selective degradation of extracellular matrix proteins during invasion. Differential expression of components of the system by cancer and non-cancer cells, regulated by paracrine mechanisms, appear to determine the involvement of the system in cancer cell-directed tissue remodeling. A detailed knowledge of these processes is necessary for utilization of the therapeutic potential of interfering with the action of the system in cancers.