Extravasation during bladder cancer metastasis requires cortactin-mediated invadopodia formation

Abstract

Abstract. Invasive cancer cells form the filamentous actin-based membrane protrusions known as invadopodia. Invadopodia are thought to play a critical role in cancer cell invasion and metastasis due to their ability to degrade the extracellular matrix. The present study assessed whether invadopodia formation is essential in extravasation of circulating bladder cancer cells and lung metastasis. To analyze the importance of invadopodia, bladder cancer cell lines with reduced invadopodia formation were established by silencing the expression of cortactin, an essential component of invadopodia, using cortactin short hairpin RNA. Bladder cancer cells with cortactin knockdown demonstrated a markedly decreased ability to form invadopodia, secrete matrix metalloproteinases and invade the extracellular matrix. In addition, the knockdown cells exhibited a reduced transendothelial invasion capacity and decreased formation of metastatic foci in the lungs. The present study demonstrated that bladder cancer cells with cortactin knockdown have a reduced capacity to extravasate into the lung from the circulation, due to the decreased invasive character of invadopodia. This suggests that invadopodia formation is a critical process for cancer cell extravasation. IntroductionThe majority of cancer mortalities are caused by metastasis. Hematogenous metastasis includes multiple steps. First, invasive cancer cells escape from the primary site into nearby blood vessels (intravasation) and disseminate around the body through the host circulation. Following this, the circulating cancer cells exit the vessels to cross the endothelia and invade secondary organ tissue (extravasation), where they proliferate to form metastases (1). It is vital to elucidate the detailed processes of these steps to prevent metastasis, however, at present, the molecular mechanisms underlying each step remain poorly understood.In order to invade surrounding tissues, invasive cancer cells form invadopodia, the filamentous actin (F-actin)-based membrane protrusions required for degradation of the extracellular matrix (ECM) and migration through the tissues (2-4). It has been reported that invadopodia play an essential role in the intravasation of cancer cells from the primary site into the blood vessels (5). However, the importance of invadopodia formation in extravasation from the blood vessels into the target organs during metastasis, remains poorly understood.In patients with aggressive bladder cancer, the most common site of hematogenous metastasis is the lungs (6). The circulating bladder cancer cells exit the lung microvessels by transendothelial invasion, to enter the lung tissue. The present study assessed whether invadopodia formation is involved in extravasation by analyzing lung metastasis of aggressive bladder cancer cells. Materials and methods Cells, reagents and antibodies.A human invasive and high-grade bladder cancer cell line, YTS-1, was provided by Dr H. Kakizaki (Yamagata University, Yamagata, Japan). YTS-1 cells were maintained in RPMI-1640 m...

LPP is a Src substrate required for invadopodia formation and efficient breast cancer lung metastasis

“…Emerging data also reveals a critical role for invadopodia in augmenting cancer cell extravasation during metastasis1325. Thus, we next investigated the potential role of LPP in promoting tumour cell extravasation using an ex ovo chick chorioallantoic membrane (CAM) assay.…”

“…Increasing evidence demonstrates that TGFβ signalling can enhance podosome formation in non-transformed cells and invadopodia formation in cancer cells153233. Invadopodia are crucial cellular structures that allow breast cancer cells to escape the primary tumour by degrading ECM components, enabling cancer cell intravasation into the circulatory system and extravasation into secondary organs12132534. Mounting evidence suggests a direct correlation between the propensity of cancer cells to form invadopodia and poor prognosis in breast cancer patients.…”

Invadosomes are coming: new insights into function and disease relevance

“…In another related study, cortactin was knocked down in a bladder cancer cell model . Invadopodia formation was significantly decreased in the cortactin knockdown cell lines, and upon tail vein injection into nude mice for an in vivo lung metastasis assay, significantly fewer metastases were detected in the lungs, providing more support for the importance of invadopodia in the extravasation process ; although it should be noted that cortactin is not exclusively localized to invadopodia.…”

“…However, podosomes have also been observed in a number of other normal cell types, including osteoclasts , aortic endothelial cells , myoblasts , bronchial epithelial cells , neural crest cells , and in neuronal growth cones . Similarly, many cancer cell types form invadopodia, including pancreatic , ovarian , prostate , brain , skin , bladder , head and neck , breast , and melanoma .…”

“…However, podosomes have also been observed in a number of other normal cell types, including osteoclasts [52,53], aortic endothelial cells [31,54], myoblasts [55], bronchial epithelial cells [56], neural crest cells [22], and in neuronal growth cones [57]. Similarly, many cancer cell types form invadopodia, including pancreatic [58], ovarian [59], prostate [16,60], brain [61], skin [62], bladder [63][64][65], head and neck [66], breast [24], and melanoma [34]. Using the proteolytic activity of its invadosomes, the cell is able to degrade the gelatin matrix (represented as cleaved, red ECM proteins).…”