Molecular pathways regulated by the ETV5 transcription factor in the invasion of endometrial cancer

Abstract

Endometrial cancer is the most frequent malignancy of the female genital tract in Western countries. The early appearance of symptoms [1], contributes to the earlier detection of this malignancy and results in better survival rates. However, in 20% of cases the diagnosis is delayed and patients present with myometrial infiltration and/or lymph node affectation. Myometrial invasion, an initial event that signals tumour invasion is one of the most valuable prognostic factors and it determines increased recurrence rates after the first surgical treatment and decreased 5-year survival. Consequently, unravelling the initial steps associated with myometrial infiltration is fundamental to identify new therapeutic agents for the prevention of cancer dissemination. To this end, the major scientific aim of our group during the past few years has been the identification of the molecular mechanisms involved in endometrial cancer invasion and dissemination. We identified ETV5 transcription factor as an important agent of myometrial invasion by endometrial tumour cells. ETV5 is specifically upregulated in invasive endometrial tumours and is able to [2] activate the metalloproteinase MMP2, thus promoting cell migration and invasion in vitro and in vivo [3]. In addition, we demonstrated the role of ETV5 on the induction of EMT, which result in the acquisition of migratory and invasive capabilities. The main objective of this thesis is to identify new molecules involved in the myometrial invasion of endometrial cancer. In particular, we have focused on the identification of new ETV5 downstream targets that mediate the role of ETV5 in the endometrial tumour cells’ acquisition of migratory and invasive properties. To further characterise the initial steps of myometrial invasion regulated by the ETV5 transcription factor, we analysed by gene expression microarray technology those genes whose expression was altered in Hec1A endometrial cancer cells with stable overexpression of a fusion GFP-ETV5 protein, compared with Hec1A control cells. In particular, we have identified NID1 and NUPR1 as direct transcriptional targets of ETV5. NID1 is a ubiquitous protein component of the BM and a partner of laminin [4]. NUPR1 is a HMG protein and its principal role in the cell is to bind to the chromatin promoters to modify the accessibility of chromatin in gene regulation [5]. We wanted to examine the role of NID1 and NUPR1 as a mediator of ETV5 functions in Hec1A endometrial cancer cells in vitro and in vivo using an orthotopic mouse model [6]. Our results suggest that NID1 regulation by ETV5 enhances cell invasion and cell adhesion to the extracellular matrix, and that NUPR1 regulation by ETV5 enhances cell migration in endometrial cancer cells in vitro. We propose that NID1 and NUPR1 regulation of cell migration and invasion may be in part mediated by the regulation of N-cadherin. We also observed that the mice injected with cells with NID1 silenced, generated a small size tumours compared with mice injected with control cells. Moreover, we found that mice injected with cells with NID1 or NUPR1 inhibition produced a decreased number of metastases compared with mice injected with control cells. These results suggest that the regulation of NID1 and NUPR1 by ETV5 contributes to the tumour progression and dissemination in vivo. Finally, in order to confirm the regulation of NID1 or NUPR1 by ETV5, we wanted to examine the role of both NID1 and NUPR1 genes in human endometrial tumour samples and their association with clinical and pathological characteristics In previous studies, ETV5 was upregulated in human endometrial tumour samples compared with control tissue, in particular in the invasion front of endometrial tumours [7]. We found that the expression of NID1 and ETV5 were clinically correlated in human endometrial tumour samples at mRNA level and at the protein level. Moreover, we observed a upregulation of NID1 and NUPR1 in invasion front of the tumour. In conclusion, the data presented in this thesis contributes to the elucidation of the molecular mechanisms involved in endometrial cancer dissemination. Understanding the molecular basis of myometrial invasion in endometrial cancer will contribute to the development of more specific and more effective therapeutic strategies.

Date of Award	19 Mar 2013
Original language	English
Supervisor	Jaime Reventos Puigjaner (Director) & Anna Ruiz (Director)