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2017 ; 16
(1
): 67
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TRIM8 restores p53 tumour suppressor function by blunting N-MYC activity in
chemo-resistant tumours
#MMPMID28327152
Mastropasqua F
; Marzano F
; Valletti A
; Aiello I
; Di Tullio G
; Morgano A
; Liuni S
; Ranieri E
; Guerrini L
; Gasparre G
; Sbisą E
; Pesole G
; Moschetta A
; Caratozzolo MF
; Tullo A
Mol Cancer
2017[Mar]; 16
(1
): 67
PMID28327152
show ga
BACKGROUND: TRIM8 plays a key role in controlling the p53 molecular switch that
sustains the transcriptional activation of cell cycle arrest genes and response
to chemotherapeutic drugs. The mechanisms that regulate TRIM8, especially in
cancers like clear cell Renal Cell Carcinoma (ccRCC) and colorectal cancer (CRC)
where it is low expressed, are still unknown. However, recent studies suggest the
potential involvement of some microRNAs belonging to miR-17-92 and its paralogous
clusters, which could include TRIM8 in a more complex pathway. METHODS: We used
RCC and CRC cell models for in-vitro experiments, and ccRCC patients and
xenograft transplanted mice for in vivo assessments. To measure microRNAs levels
we performed RT-qPCR, while steady-states of TRIM8, p53, p21 and N-MYC were
quantified at protein level by Western Blotting as well as at transcript level by
RT-qPCR. Luciferase reporter assays were performed to assess the interaction
between TRIM8 and specific miRNAs, and the potential effects of this interaction
on TRIM8 expression. Moreover, we treated our cell models with conventional
chemotherapeutic drugs or tyrosine kinase inhibitors, and measured their response
in terms of cell proliferation by MTT and colony suppression assays. RESULTS: We
showed that TRIM8 is a target of miR-17-5p and miR-106b-5p, whose expression is
promoted by N-MYC, and that alterations of their levels affect cell
proliferation, acting on the TRIM8 transcripts stability, as confirmed in ccRCC
patients and cell lines. In addition, reducing the levels of
miR-17-5p/miR-106b-5p, we increased the chemo-sensitivity of RCC/CRC-derived
cells to anti-tumour drugs used in the clinic. Intriguingly, this occurs, on one
hand, by recovering the p53 tumour suppressor activity in a TRIM8-dependent
fashion and, on the other hand, by promoting the transcription of miR-34a that
turns off the oncogenic action of N-MYC. This ultimately leads to cell
proliferation reduction or block, observed also in colon cancer xenografts
overexpressing TRIM8. CONCLUSIONS: In this paper we provided evidence that TRIM8
and its regulators miR-17-5p and miR-106b-5 participate to a feedback loop
controlling cell proliferation through the reciprocal modulation of p53, miR-34a
and N-MYC. Our experiments pointed out that this axis is pivotal in defining drug
responsiveness of cancers such ccRCC and CRC.