Abstract
Simple SummaryColorectal cancer (CRC) is one of the most common malignancies in the digestive system. We have previously shown that the proprotein convertase Furin is involved in calcium regulation in cancer cells. In this study, we revealed that the malignant phenotype of colon cancer stem cells is repressed by Furin inhibition that is associated with reduced expression of LGR5 and Nanog and dysregulated expression of several calcium regulators involved in colon cancer. Our data support the idea that targeting Furin in colorectal cancer stem cells may constitute a potential therapeutic approach.Proprotein convertases or PCs are known to regulate the malignant phenotype of colon cancer cells by different mechanisms, but their effects on cancer stem cells (CSCs) have been less widely investigated. Here, we report that PCs expression is altered in colon CSCs, and the inhibition of their activity reduced colon CSCs growth, survival, and invasion in three-dimensional spheroid cultures. In vivo, repression of PCs activity by the general PC inhibitors α1-PDX, Spn4A, or decanoyl-RVKR-chloromethylketone (CMK) significantly reduced tumor expression levels of the stem cell markers LGR5 and NANOG that are associated with reduced tumor xenografts. Further analysis revealed that reduced tumor growth mediated by specific silencing of the convertase Furin in KRAS or BRAF mutated-induced colon tumors was associated with reduced expression of LGR5 and NANOG compared to wild-type KRAS and BRAF tumors. Analysis of various calcium regulator molecules revealed that while the calcium-transporting ATPase 4 (ATP2B4) is downregulated in all the Furin-silenced colon cancer cells, the Ca2+-mobilizing P2Y receptors, was specifically repressed in BRAF mutated cells and ORAI1 and CACNA1H in KRAS mutated cells. Taken together, our findings indicate that PCs play an important role in the malignant phenotype of colon CSCs and stem cell markers’ expression and highlight PCs repression, particularly of Furin, to target colon tumors with KRAS or BRAF mutation.
Highlights
Colorectal cancer (CRC) is the second leading cause of mortality among cancer patients in the world and is the third most diagnosed cancer globally [1]
To determine whether proprotein convertases (PCs) expression in cancer stem cells (CSCs) is altered, spheres were generated from the parental colon cancer cells SW480 (Figure 1a), SW620 (Figure 1b), HT-29, (Figure 1c), and CT-26 (Figure 1d)
Since CSC markers, LGR5 and NANOG have been shown to be progressively expressed during carcinogenesis and promote cancer cell proliferation and tumor formation [22,39], we evaluated the impact of PCs repression in tumor cells on LGR5 and NANOG expression during tumor progression
Summary
Colorectal cancer (CRC) is the second leading cause of mortality among cancer patients in the world and is the third most diagnosed cancer globally [1]. No single cause for CRC has been identified but it results from the cumulative effects of multiple and sequential genetic alterations These include mutations of the tumor suppressor gene adenomatous polyposis coli (APC) and the proto-oncogene KRAS, allowing the activation of Wnt/βcatenin and Ras/ERK pathways, respectively [2,3,4]. CSCs were reported to derive from oncogenic reprogramming of normal stem cells, where various stemness factors, such as NANOG and LGR5, which play a key role are expressed Altered expression of these stemness factors was found to mediate CSCs malignant phenotype acquisition and tumor progression [11,12,13]. NANOG overexpression in colorectal CSCs was found to promote tumorigenicity in preclinical models [19]
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