SPOCK1 promotes breast cancer progression via interacting with SIX1 and activating AKT/mTOR signaling pathway

Abstract

SPOCK1 is highly expressed in many types of cancer, which has been recognized as a promoter of cancer progression, while its regulatory mechanism remains to be clear in breast cancer (BC). This study aimed to explore the precise function of SPOCK1 in BC progression and the mechanism by which SPOCK1 was involved in cell proliferation and epithelial-mesenchymal transition (EMT).Immunohistochemistry (IHC) and database analysis displayed that high expression of SPOCK1 was positively associated with histological grade, lymph node metastasis (LN) and poor clinical prognosis in BC. A series of assays both in vitro and in vivo elucidated that altering SPOCK1 level led to distinctly changes in BC cell proliferation and metastasis. Investigations of potential mechanisms revealed that SPOCK1 interacted with SIX1 could enhance cell proliferation, cell cycle and EMT process by activating the AKT/mTOR pathway, whereas inhibition of AKT/mTOR pathway or depletion of SIX1 reversed the effects of SPOCK1 overexpression.Furthermore, SPOCK1 and SIX1 were highly expressed in BC and might indicate poor prognoses. Altogether, SPOCK1/SIX1 promoted BC progression by activating AKT/mTOR pathway to accelerate cell proliferation and metastasis in BC, and SPOCK1/SIX1 might be promising clinical therapeutic targets to prevent BC progression. IMPORTANCE:The incidence of BC is alarmingly high and many patients initially diagnosed without detectable metastases will eventually develop metastatic lesions. The occurrence of metastasis is responsible for the death of many patients, which also represents a big challenge for researchers to improve the survival rates of BC patients.Hence the scientific community pays more attention on cancer targeted therapy. This research is significant for identifying the underlying mechanisms and capabilities of SPOCK1-induced BC activities, which will greatly apply novel targets and new treatment strategies for clinicians, leading to broader biomedical impacts. KEYWORDS: SPOCK1; SIX1; EMT; Breast cancer; AKT/mTOR signaling pathwayBreast cancer (BC), the most frequently diagnosed lethal gynecologic malignancy in women worldwide (1), which is an increasing concern because of its rising incidence. Despite major advances in BC therapy, the prognosis for most patients would be significantly worse once spread metastasized occurs (2). Metastasis is the mainspring for most patient death and represents the fundamental challenge of the clinical treatment for the patients with BC. The initiation and metastasis of BC are intricate processes, which triggered by multiple genes and intracellular signal transduction cross-talks. Thus, looking for valid molecular hallmarks and understanding the mechanisms of BC initiation and metastasis process are urged to put on the agenda. Sparc/osteonectin, cwcv and kazal-like domains proteoglycan 1 (SPOCK1), is also known as TIC1; SPOCK; TESTICAN, belongs to multidomain testicular proteoglycan family (3). This protein family includes SPARC, TESTICAN-2, and TESTICAN-3, which are associated with ...

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“…It is also associated with tumor-associated kinases, microRNAs, and transcription factors [37]. NUSAP1 can inhibit the proliferation, migration, and invasion and promote the apoptosis of tumor cells by inhibiting the AKT/mTOR signaling pathway in lung cancer cells [38]. The downregulation of NUSAP1 promotes apoptosis and inhibits proliferation, migration, and invasion in NSCLC cells, which is associated with the regulation of the BTG2/PI3K/Akt signaling pathway [39].…”