Pre-Clinical Study, Oncology group Extracellular matrix and pituitary tumorogenesis I

GRACIELA DÍAZ DE TORGA

2008-03-12

2010-03-30

Biológica

Prom.Gral.del Conoc.-Cs.Medicas

<!-- /* Font Definitions */ @font-face {font-family:Wingdings; panose-1:5 0 0 0 0 0 0 0 0 0; mso-font-charset:2; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:0 268435456 0 0 -2147483648 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; mso-layout-grid-align:none; punctuation-wrap:simple; text-autospace:none; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US; mso-fareast-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} /* List Definitions */ @list l0 {mso-list-id:671033530; mso-list-type:hybrid; mso-list-template-ids:-760822498 1928077764 201981955 201981957 201981953 201981955 201981957 201981953 201981955 201981957;} @list l0:level1 {mso-level-start-at:0; mso-level-number-format:bullet; mso-level-text:-; mso-level-tab-stop:36.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @list l0:level2 {mso-level-number-format:bullet; mso-level-text:o; mso-level-tab-stop:72.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:"Courier New";} @list l0:level3 {mso-level-number-format:bullet; mso-level-text:; mso-level-tab-stop:108.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:Wingdings; mso-bidi-font-family:"Times New Roman";} @list l0:level4 {mso-level-number-format:bullet; mso-level-text:; mso-level-tab-stop:144.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:Symbol; mso-bidi-font-family:"Times New Roman";} @list l0:level5 {mso-level-number-format:bullet; mso-level-text:o; mso-level-tab-stop:180.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:"Courier New";} @list l0:level6 {mso-level-number-format:bullet; mso-level-text:; mso-level-tab-stop:216.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:Wingdings; mso-bidi-font-family:"Times New Roman";} @list l0:level7 {mso-level-number-format:bullet; mso-level-text:; mso-level-tab-stop:252.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:Symbol; mso-bidi-font-family:"Times New Roman";} @list l0:level8 {mso-level-number-format:bullet; mso-level-text:o; mso-level-tab-stop:288.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:"Courier New";} @list l0:level9 {mso-level-number-format:bullet; mso-level-text:; mso-level-tab-stop:324.0pt; mso-level-number-position:left; text-indent:-18.0pt; font-family:Wingdings; mso-bidi-font-family:"Times New Roman";} ol {margin-bottom:0cm;} ul {margin-bottom:0cm;} --> The main objetive of our whole proyect is to study the processes involved in pituitary tumorogenesis, in order to obtain new therapeutic targets in treatments against tumour growth, invasion and metastasis. During the last decade lots of studies have demonstrated a strong association between  tumour  growth and an alterated regulation and function of angiogenic factors, metalloproteinases (MMPs) and extracellular matrix (EM) components (3, 4). On this basis, we want to study the expression, localization, function and interaction of angiogenic and antiangiogenic factors, growth factors (GFs), MMPs and EM components in a tumor model that, in general, does NOT develop metastasis: prolactinomas.  This special characteristic is surely regulated by mechanisms involving all components mentioned above. The knowledge of this regulatory mechanisms that lead to a phenotype that “does not develop metastasis” would be a  key tool  not only to look for new therapeutic treatments in resistant prolactinomas, but in therapies for a diversity of aggressive and metastasic tumours. Pituitary adenoma growth, as in all tumors, depends on adequate neovascularization. Angiogenesis is regulated by stimulators and inhibitors and involve multiple biological processes including endothelial cell proliferation, migration, cell-cell and cell-matrix adhesion, assembly into tube structures as well as apoptosis. In rats it has been shown that estrogen-induced prolactin-secreting pituitary tumors are highly angiogenic (5), and furthermore, tumor growth can be blocked by antiangiogenic agents (6;7). Cytokines and growth factors are important modulators of angiogenesis. We have recently described the involvement of  three main angiogenic factors: VEGF, FGF2 and Pttg  (see 9, 10 and 11 respectively) in prolactinoma development in an experimental mouse model..   A- In the same line, we are now interested in studing the expression, function and the interaction with GFs  of one of the main antiangiogenic factors: Thrombospondin 1  (TSP1) in pituitary tumorogenesis. These studies will be developed in two different experimental models of lactotrope hyperplasia with altered dopaminergic control of the pituitary: -          the dopaminergic receptor 2 (D2R)  knockout female mouse -          the estrogen-treated rat.  These models share the characteristics of increased pituitary weight, hyperprolactinemia, lactotrope hyperplasia and reduced or absent dopaminergic action at the pituitary level. The estrogen-treated rat is an interesting and well known model of pituitary hyperplasia induced by chronic estrogen stimulation. Estradiol not only increases lactotrope proliferation rate, but induces angiogenic factor local expression  (VEGF and FGF2) (12, 13, 14). <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; mso-layout-grid-align:none; punctuation-wrap:simple; text-autospace:none; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US; mso-fareast-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> On the other hand, the D2R female knockout mouse is an excellent model to study prolactinoma development. Female KO mice develop lactotrope hyperplasia followed by lactotrope tumor formation according to the lack of dopaminergic inhibitory control (8, 15, 16). In a previous work we demonstrated that pituitary glands of the female D2R knockout mice  have markedly increased number of cells containing prolactin. Furthermore, we described increased pituitary VEGF-A expression in correlation with increased peliosis and vascularization of the gland (9).   Thrombospondin-1 (TSP-1), a multifunctional matrix glyco-protein, is secreted by most epithelial cells and acts as a multifunctional inhibitor of angiogenesis controlling tumor growth in various tissues (17).  It has direct effects via CD36 on activated endothelial cells, inhibiting migration, inducing apoptosis and inhibiting growth factor mobilization/ access to the cell surface; it may also downregulate cell survival pathways. Thus, TSP-1 significantly attenuates tumor progression and metastasis. The  endogenous angiogenic inhibitor TSP1 participates  in mammary tumor progression. This was studied  generating mammary tumor-prone mice that either lack, or specifically overexpress, TSP1 in the mammary gland. Tumor burden and vasculature were significantly increased in TSP1-deficient animals, and capillaries within the tumor appeared distended and sinusoidal. In contrast, TSP1 overexpressors showed delayed tumor growth or lacked frank tumor development; tumor capillaries showed reduced diameter and were less frequent. Interestingly, absence of TSP1 resulted in increased association of VEGF with its receptor VEGFR2 and higher levels of active matrix metalloproteinase-9 (MMP9), a molecule previously shown to facilitate both angiogenesis and tumor invasion. In vitro, enzymatic activation of proMMP9 was suppressed by TSP1. Together these results argue for a protective role of endogenous inhibitors of angiogenesis in tumor growth and implicate TSP1 in the in vivo regulation of metalloproteinase-9 activation and VEGF signaling (18).