MiR-505 mediates methotrexate resistance in colorectal
cancer by targeting RASSF8
, Li Bian
and Yingmei Zhang
Department of Oncology, The Fifth People’s Hospital of Ji’nan, and
Department of Science and Education, Shandong Cancer Hospital Afﬁliated
to Shandong University, Shandong Academy of Medical Sciences, Ji’nan, China
colorectal cancer; methotrexate; miR-505;
Yalin Chen, Department of Oncology, The
Fifth People’s Hospital of Ji’nan, No. 24297
Jingshi Road, Huaiyin District, Ji’nan
250022, Shandong, China.
Received September 29, 2017
Accepted January 12, 2018
Objective To investigate the relationship between miR-505 and RASSF8 as well
as the effect of miR-505 on methotrexate (MTX) resistance of human colorectal
Methods Microarray was used to select differentially expressed miRNAs. QRT-
PCR and western blot were performed to assess miR-505 and RASSF8 mRNA
levels in MTX-sensitive and MTX-resistant CRC tissues and cells. Cell viability,
propagation and apoptosis were conﬁrmed by MTT, colony formation assays
and ﬂow cytometry. Transwell and wound healing assays were conducted on
cancerous cells to determine cell metastasis. The target relationship between
miR-505 and RASSF8 was validated using dual-luciferase reporter gene assay.
Key ﬁndings MiR-505 expression signiﬁcantly increased in resistant tissues com-
pared with sensitive tissues. Down-regulation of miR-505 expression weakened
the proliferation ability of LS174T and LS174T/MTX cells, induced cell cycle
arrest and apoptosis rate. RASSF8 was a target of miR-505 and overexpression of
miR-505 down-regulated RASSF8 mRNA and protein expression. Overexpression
of RASSF8 could affect the cycle of CRC cells, accelerate apoptosis as well as
restrain migration and invasion. Moreover, miR-505 advanced MTX-induced
LS174T cells migration and invasiveness as well as depressed LS174T/MTX cell
apoptosis through the down-regulation of RASSF8.
Conclusion MiR-505 mediated MTX resistance, propagation, cell cycle and
metastasis by targeting RASSF8 in colorectal cancer.
Colorectal cancer (CRC) is the fourth most prevalent and
one of the most fatal human malignancies all over the
with the incidence rates increasing rapidly in
Anti-cancer drugs have been created to
improve the prognosis outcomes of CRC patients. How-
ever, the recurrence of colon cancer remains a higher level
partially owing to the stronger drug resistance. Many mech-
anisms have also been considered to be responsible for drug
resistance, such as inhibition of apoptosis, alternations in
cell cycle, activation of detoxiﬁcation and so on.
theless, the mechanisms pertinent to underlying therapy
resistance CRC still need to be further elucidated.
MiRNAs are short (19–25 nt long) non-coding RNA
molecules that modulate gene expression by transcriptional
repression of mRNA.
In various types of human cancers,
miRNAs have been demonstrated to be involved in critical
stages of cancer progression and the regulatory processes of
gene expression, such as cell proliferation, apoptosis and
migration, suggesting their potential oncogenic or tumour
suppressive roles in cancer progression.
studies have also substantiated that dysregulation of
miRNA is correlated with cancer cell growth and metasta-
sis. For instance, miR-506 was reported to overexpress in
human colorectal cancer cells, thereby inhibiting cancer cell
while miR-9 was suggested to inhibit cell
invasiveness by down-regulating TM4SF1 in CRC
et al. also veriﬁed that miR-505 up-regulation suppressed
cervical cancer proliferation and invasion.
RASSF8 is one of the 10 members of the Ras-association
domain family (RASSF), several of which are thought to be
tumour suppressor genes,
including RASSF8. Previous
study has shown that RASSF8 is ubiquitously expressed in
© 2018 Royal Pharmaceutical Society, Journal of Pharmacy and Pharmacology, 70 (2018), pp. 937–951