Extracellular HSP70 blocks CD40L-induced apoptosis and tubular formation in endothelial cells

The complex function of hsp70 in metastatic cancer

Elevated expression of the inducible heat shock protein 70 (Hsp70) is known to correlate with poor prognosis in many cancers. Hsp70 confers survival advantage as well as resistance to chemotherapeutic agents, and promotes tumor cell invasion. At the same time, tumor-derived extracellular Hsp70 has been recognized as a "chaperokine", activating antitumor immunity. In this review we discuss localization dependent functions of Hsp70 in the context of invasive cancer. Understanding the molecular principles of metastasis formation steps, as well as interactions of the tumor cells with the microenvironment and the immune system is essential for fighting metastatic cancer. Although Hsp70 has been implicated in different steps of the metastatic process, the exact mechanisms of its action remain to be explored. Known and potential functions of Hsp70 in controlling or modulating of invasion and metastasis are discussed.

Serum heat shock protein 70 levels in relation to circulating cytokines, chemokines, adhesion molecules and angiogenic factors in women with preeclampsia

BACKGROUND

We have previously reported that serum levels of 70 kDa heat shock protein (Hsp70, HSPA1A) are increased and reflect systemic inflammation, oxidative stress and hepatocellular injury in preeclampsia. The purpose of this study was to determine whether increased serum Hsp70 concentrations in women with preeclampsia are related to circulating levels of cytokines, chemokines, adhesion molecules and angiogenic factors, the key players in the pathogenesis of the disease.

METHODS

Sixty preeclamptic patients and 60 normotensive, healthy pregnant women were involved in this case-control study. Levels of Hsp70 (HSPA1A) and transforming growth factor (TGF)-beta1 in maternal sera were assessed by ELISA. Serum levels of interleukin (IL)-1 beta, IL-1 receptor antagonist, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p40, IL-12p70, IL-18, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interferon-gamma-inducible protein (IP)-10, monocyte chemotactic protein (MCP)-1, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 were determined by multiplex suspension array. Serum total soluble fms-like tyrosine kinase-1 (sFlt-1) and biologically active placental growth factor (PlGF) levels were measured by electrochemiluminescence immunoassay. For statistical analyses, the Mann-Whitney U-test, the Fisher exact and Pearson chi-square tests, the Spearman rank order correlation, multiple linear regression and logistic regression were applied.

RESULTS

Serum levels of Hsp70 were significantly higher in preeclamptic patients than in healthy pregnant women. Additionally, most of the measured inflammatory variables differed significantly between the two study groups except for serum IL-1 beta and TGF-beta1 levels and IL-18/IL-12p70 and IL-12p70/IL-12p40 ratios, indicating a bias toward a pro-inflammatory status in preeclampsia. Preeclamptic patients had significantly higher sFlt-1 levels and sFlt-1/PlGF ratio and significantly lower PlGF concentrations as compared to healthy pregnant women. In the preeclamptic group, serum Hsp70 concentrations showed significant correlations with serum levels of IL-12p40 (R=0.59, p<0.001), MCP-1 (R=0.43, p<0.001), ICAM-1 (R=0.39, p=0.0020) and VCAM-1 (R=0.46, p<0.001). Furthermore, elevated serum Hsp70 level and sFlt-1/PlGF ratio had a synergistic (joint) effect in the risk of preeclampsia, as shown by the substantially higher odds ratios of their combination than of either alone.

CONCLUSIONS

Increased serum Hsp70 concentrations in women with preeclampsia were associated with pro-inflammatory changes in circulating cytokine profile, suggesting that circulating Hsp70 might contribute to the development of the excessive systemic inflammatory response characteristic of the maternal syndrome of the disease.

The regulatory mechanism of extracellular Hsp90{alpha} on matrix metalloproteinase-2 processing and tumor angiogenesis

Heat shock protein 90α (Hsp90α) is a ubiquitously expressed molecular chaperone that is essential for eukaryotic homeostasis. Hsp90α can also be secreted extracellularly, where it has been shown to be involved in tumor metastasis. Extracellular Hsp90α interacts with and promotes the proteolytic activity of matrix metalloproteinase-2 (MMP-2). However, the regulatory mechanism of Hsp90α on MMP-2 activity is still unknown. Here we show that Hsp90α stabilizes MMP-2 and protects it from degradation in tumor cells. Further investigation reveals that this stabilization effect is isoform-specific, ATP-independent, and mediated by the interaction between the Hsp90α middle domain and the MMP-2 C-terminal hemopexin domain. Moreover, this mechanism also applies to endothelial cells that secrete more Hsp90α in their proliferating status. Furthermore, endothelial cell transmigration, Matrigel plug, and tumor angiogenesis assays demonstrate that extracellular Hsp90α promotes angiogenesis in an MMP-2-dependent manner. In sum, this study provides new insights into the molecular mechanism of how Hsp90α regulates its extracellular client proteins and also reveals for the first time the function of extracellular Hsp90α in promoting tumor angiogenesis.