HSP27 Regulation of Breast Tumor Blood Vessel Growth

Institution: Scripps Research Institute
Investigator(s): Randolph Piotrowicz, Ph.D. -
Award Cycle: 1995 (Cycle I) Grant #: 1FB-0367 Award: $75,570
Award Type: Postdoctoral Fellowship
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease

Initial Award Abstract (1995)
The growth and spread of breast cancer is dependent on the establishment of a blood supply to the cancerous tumor. This is accomplished by the extension of existing blood vessels into the tumor mass by the migration and growth of the endothelial cells which line the intruding blood vessels. Highly vascularized tumors are generally larger and more likely to spread to other organs. The extent of tumor vascularization, therefore, is correlative with the risk of morbidity. Understanding how the generation of a tumor blood supply is regulated is essential to the understanding of the progression of the disease and may provide future avenues of prevention. Work in our laboratory has identified a small heat shock protein (HSP27) as a potential regulator of vessel growth. Increasing HSP27 levels by placing the human gene into bovine arterial endothelial cells results in enhanced growth and migration. HSP27 has been of interest to cancer researchers and oncologists because estrogen treatment of certain breast cancer cells, which causes accelerated growth of these cells, also causes increased HSP27 production. Since endothelial cell HSP27 is also responsive to estrogen, we propose that endothelial cell HSP27 regulates the vascularization of tumors which generate estrogen and/or grow in a milieu where estrogen is a key regulatory factor, e.g., breast carcinoma.

To test this hypothesis, the following is proposed. First, the effects of estrogen treatment or the co-culture of breast cancer cells on the growth and migration of endothelial cells producing elevated HSP27 levels or mutant HSP27 will be measured. In addition, the effect of lowering endothelial cell HSP27 levels (through the infection of adenovirus vectors carrying anti-sense DNA) on these processes will be tested. Second, culture conditions will be modified to support the formation of capillary-like structures. The effect of estrogen or co-cultured breast tumor cells on the generation of these structures will be measured. Finally, mice expressing human HSP27 in addition to mouse HSP27 will be used to test the effect of elevated endothelial cell HSP27 levels on the formation of new blood vessels. The effect of elevated circulating and local estrogen levels (the latter approximating the effect of tumor-generated estrogen) will also be assessed. These studies address the complex communications which occur between breast tumor cells and invading vascular cells and will delineate the role of a key player in breast tumor vascularization.

Final Report (1997)
The generation of a blood supply to a tumor positively affects its growth, progression, and spread (metastasis). Endothelial cells, the cells that line blood vessels, are therefore a focus of research designed to understand and control tumor vascularization. This study specifically addresses the role of the endothelial cell protein HSP27 in the generation of a tumor blood supply (angiogenesis). In order for a breast tumor to grow beyond a small mass of cells, the tumor must recruit existing breast capillaries into the tumor. While many of the key factors that regulate endothelial cell growth and migration have been well characterized, few cellular proteins which respond to these regulators and induce changes in endothelial cell behavior that result in the generation of new blood vessels have been identified. Endothelial cell HSP27, whose synthesis is enhanced in response to estrogen (a key factor in breast tumor growth and angiogenesis), contributes to the regulation of angiogenic processes by providing mechanisms which can either enhance or inhibit endothelial cell migration.

In our project we study, (i) the role of normal and mutant HSP27 protein in regulating endothelial cell migration and (ii) the role of estrogen and breast tumor cell lines in affecting HSP27-dependent endothelial cell migration. To assess endothelial cell migration, we use a tissue culture model system that measures the movement of bovine endothelial cells into an area scraped clean of cells. Cells containing the human gene for HSP27 (and therefore producing elevated levels of HSP27) migrate faster into the area devoid of cells than control cells. Production of a mutant form of HSP27 inhibited cell migration. Endothelial cells producing either of these gene products have aberrant structural components that give the cell its shape and also function in many other processes including cell migration. That the enhanced migration rate of HSP27-producing cells is due to the effect HSP27 has on these structural elements is currently being tested.

In contrast, HSP27 can also inhibit cell migration by mediating the release of a growth factor (known as high molecular weight basic-fibroblast growth factor, HMW b-FGF) when the cells are treated with estrogen. Purified HMW b-FGF or that released by estrogen-treated HSP27-producing cells stimulates the growth of breast tumor and endothelial cells, but inhibits the migration of cells in the culture assay. Importantly, we have also recently demonstrated that this factor inhibits the migration of tumor cells, and thus may have a role in regulating tumor metastasis. How HMW b-FGF functions to inhibit endothelial cell migration and the exact role of HSP27 in mediating its release are currently being elucidated.

Since the incidence of metastasis and death increases as breast tumors become vascularized, the identification of mechanisms that regulate tumor blood vessel growth has impact on current therapies and may lead to new treatment avenues.

Fluid shear stress induces the phosphorylation of small heat shock proteins in vascular endothelial cells
Periodical:American Journal of Physiology
Index Medicus: Am J Physiol
Authors: Li S, Piotrowicz, Levin EG, Shyy YJ, Chien S
Yr: 1996 Vol: 271 Nbr: Abs: Pg:994-1000

Basolateral membrane-associated 27-kDa heat shock protein and microfilament polymerization
Periodical:Journal of Biological Chemistry
Index Medicus: J Biol Chem
Authors: Piotrowicz RS, Levin EG
Yr: 1997 Vol: 272 Nbr: 41 Abs: Pg:25920-7

The 27-kDa heat shock protein facilitates basic fibroblast growth factor release from endothelial cells.
Periodical:Journal of Biological Chemistry
Index Medicus: J Biol Chem
Authors: Piotrowicz RS, Martin JL, Dillman WH, Levin EG.
Yr: 1997 Vol: 272 Nbr: 11 Abs: Pg:7042-7

Dual activities of 22-24 kDa basic-fibroblast growth factor: Inhibition of migration and stimulation of proliferation
Periodical:FASEB Journal
Index Medicus: FASEB J
Authors: Piotrowicz RS, PA Maher and EG Levin
Yr: 1998 Vol: 12 Nbr: Abs: Pg:1481-1490