Discussion
Many studies have shown that miRNAs have an important role in the
development of human cancers. For example, miRNAs can regulate cancer
metastasis by affecting cancer cell migration, invasion, angiogenesis
and proliferation.18 MiRNAs also regulate macrophages,
a crucial component in the innate immune system, to control cell
differentiation, phagocytosis and apoptosis, implying a promising
therapy target to fight against cancers.19 At present,
miRNAs have been used as diagnostic and prognostic biomarkers in
different cancers, including colorectal cancer, digestive tract cancers,
hepatic cancer stem cells and oesophageal cancer.20 In
hypopharyngeal cancer , there has been some studies reporting roles of
miRNAs. Fukumoto et al. discovered that miR-451a was significantly
inhibited in hypopharyngeal cancer.21 Kikkawa et al.
showed that miR-489 could suppress tumor development by targeting PTPN11
in hypopharyngeal cancer.22 The role of miR-21 has not
yet been revealed in hypopharyngeal cancer although abnormal increase of
miRNA-21 expression level has been detected in a variety of tumor
specimens and cell lines, including breast cancer, cervical cancer, lung
cancer, pancreatic cancer, prostate cancer, colorectal cancer and
glioma. Here, we demonstrated that the expression of miR-21
significantly increased in human hypopharyngeal cancer tissues, and this
increase was closely related to the transition of hBMSCs to CAFs.
We firstly found that miR-21 was up-regulated in hypopharyngeal cancer
tissue and FaDu cells. Further understanding of this novel biomarker
miR-21 and its associated function could potentially provide new
insights into future applications to the prevention of the
hypopharyngeal cancer. Our continued studies found that exosomes from
FaDu cells could mediate induction of CAF-like features in hBMSCs after
co-culture of FaDu cell exosomes and hBMSCs. In this experiment, we
detected high expression level of CAF-related markers, includingα-SMA
and FAP, and increased number of CAF-like cells. Flow cytometry results
showed that the cell proportion of G1 phase in FaDu-exo+BMSC group was
significantly decreased, while the cell proportion of G2 phase was
significantly increased compared to the control.
Our findings further confirmed that it’s miR-21 that mediated induction
of CAF-like features in hBMSCs. We co-cultured BMSCs and exosomes in
which miR-21 was knocked out and found that expression level of α-SMA
and FAP decreased and the number of CAF-like cells was significantly
decreased. Flow cytometry results showed that the cell proportion of G1
phase in miR-21 inhibitor-treated group was significantly increased,
while the cell proportion of G2 phase was significantly decreased
compared to the control.