Loss of Kaiso expression in breast cancer cells prevents intra-vascular invasion in the lung and secondary metastasis.

Jacek M Kwiecien,Blessing I Bassey-Archibong,Wojciech Dabrowski,Lyndsay G Rayner,Juliet M Daniel,Alexandra R Lucas

doi:10.1371/journal.pone.0183883

Jacek M Kwiecien, Blessing I Bassey-Archibong + Show 4 more

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https://doi.org/10.1371/journal.pone.0183883

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Abstract

The metastatic activity of breast carcinomas results from complex genetic changes in epithelial tumor cells and accounts for 90% of deaths in affected patients. Although the invasion of the local lymphatic vessels and veins by malignant breast tumor cells and their subsequent metastasis to the lung, has been recognized, the mechanisms behind the metastatic activity of breast tumor cells to other distal organs and the pathogenesis of metastatic cancer are not well understood. In this study, we utilized derivatives of the well-established and highly metastatic triple negative breast cancer (TNBC) cell line MDA-MB-231 (MDA-231) to study breast tumor metastasis in a mouse model. These MDA-231 derivatives had depleted expression of Kaiso, a POZ-ZF transcription factor that is highly expressed in malignant, triple negative breast cancers. We previously reported that Kaiso depletion attenuates the metastasis of xenografted MDA-231 cells. Herein, we describe the pathological features of the metastatic activity of parental (Kaisopositive) versus Kaisodepleted MDA-231 cells. Both Kaisopositive and Kaisodepleted MDA-231 cells metastasized from the original tumor in the mammary fat pad to the lung. However, while Kaisopositive cells formed large masses in the lung parenchyma, invaded large pulmonary blood vessels and formed secondary metastases and large tumors in the distal organs, Kaisodepleted cells metastasized only to the lung where they formed small metastatic lesions. Importantly, intravascular invasion and secondary metastases in distal organs were not observed in mice xenografted with Kaisodepleted cells. It thus appears that the lung may constitute a barrier for less invasive breast tumors such as the Kaisodepleted TNBC cells; this barrier may limit tumor growth and prevents Kaisodepleted TNBC cells from invading the pulmonary blood vessels and forming secondary metastases in distal organs.

Highlights

An estimated 90% of medical fatalities in cancer patients are due to metastases [1]
epithelial-to-mesenchymal transformation (EMT) is frequently accompanied by loss of the epithelial marker E-cadherin, concurrent with elevated expression of vimentin [41,42,43,44,45], an intermediate filament that participates in cell motility [46], as well as increased expression of matrix metalloproteases-2 and -9 (MMP-2, MMP-9) [27,28,29,30,31,32] that are often assessed in the determination of poor prognosis in breast cancer patients [33,34,35,36]
To gain insight into the mechanisms involved in breast tumor metastases to distant organs, we studied the pathogenesis of secondary metastases of parental, Kaisopositive and experimental Kaisodepleted MDA-231 triple negative breast cancer (TNBC) cells in immunocompromised mice [53]

Summary

Introduction

An estimated 90% of medical fatalities in cancer patients are due to metastases [1]. Carcinomas of the mammary gland [2,3], prostate gland [4], liver [5,6,7,8,9], pancreas [10], endometrium [11], thyroid gland [12,13] and Merkel cell [14] have been shown to invade lymphoid vessels and blood vessels [2,6,8,9,11,12,13,14] resulting in metastases to distant organs, the lung [7,9]. Characterization of the mechanisms of malignant mammary carcinoma indicates that in the primary tumor, a small population of cells travel towards the blood vessels, and invade them in a complex process involving enhanced activity of genes regulating the dynamics of the actin cytoskeleton, e.g. Mena [2,15,16,17] and LIM kinase1 [18]. EMT is frequently accompanied by loss of the epithelial marker E-cadherin, concurrent with elevated expression of vimentin [41,42,43,44,45], an intermediate filament that participates in cell motility [46], as well as increased expression of matrix metalloproteases-2 and -9 (MMP-2, MMP-9) [27,28,29,30,31,32] that are often assessed in the determination of poor prognosis in breast cancer patients [33,34,35,36]. Tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA) are known to activate pro-enzyme forms of MMP-2 and MMP-9 to active forms [37,38] and tPA and uPA have been proposed as markers for breast cancer progression [39,40]

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