Abstract
CD133, known as prominin1, is a penta-span transmembrane glycoprotein presumably a cancer stem cell marker for carcinomas, glioblastomas, and melanomas. We showed that CD133(+) ‘melanoma-initiating cells’ are associated with chemoresistance, contributing to poor patient outcome. The current study investigates the role(s) of CD133 in invasion and metastasis. Magnetic-activated cell sorting of a melanoma cell line (BAKP) followed by transwell invasion assays revealed that CD133(+) cells are significantly more invasive than CD133(−) cells. Conditional reprogramming of BAKP CD133(+) cells maintained stable CD133 overexpression (BAK-R), and induced cancer stem cell markers, melanosphere formation, and chemoresistance to kinase inhibitors. BAK-R cells showed upregulated CD133 expression, and consequently were more invasive and metastatic than BAK-P cells in transwell and zebrafish assays. CD133 knockdown by siRNA or CRISPR-Cas9 (BAK-R-T3) in BAK-R cells reduced invasion and levels of matrix metalloproteinases MMP2/MMP9. BAK-R-SC cells, but not BAK-R-T3, were metastatic in zebrafish. While CD133 knockdown by siRNA or CRISPR-Cas9 in BAK-P cells attenuated invasion and diminished MMP2/MMP9 levels, doxycycline-induced CD133 expression in BAK-P cells enhanced invasion and MMP2/MMP9 concentrations. CD133 may therefore play an essential role in invasion and metastasis via upregulation of MMP2/MMP9, leading to tumor progression, and represents an attractive target for intervention in melanoma.
Highlights
IntroductionMelanoma is a deadly form of cancer, with 23,000 cases and 7320 deaths in the United States
Melanoma is a deadly form of cancer, with 23,000 cases and 7320 deaths in the United States.In 16 other countries such as Australia and New Zealand, melanoma incidence and death rates are even higher [1]
BRAFWT /NRASQ61K melanoma cells were derived from a patient (BAK parental (BAK-P) cell line), and separated by magnetic-activated cell sorting (MACS) into CD133(+) and CD133(−) subpopulations
Summary
Melanoma is a deadly form of cancer, with 23,000 cases and 7320 deaths in the United States. In 16 other countries such as Australia and New Zealand, melanoma incidence and death rates are even higher [1]. Patient survival decreases with progression of the disease. Hallmarks of progression, are key factors that determine clinical outcomes. Some genes alter the course of early stages of tumorigenesis along with metastasis, while others exert their effects on progression alone [5]. Some inducers of metastasis, such as BMI, induce sets of genes that generate a cancer stem cell phenotype [4], indicating a connection between stemness and cancer progression
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