Antitumor and off-target effects of cholesterol-conjugated let-7a mimics in an orthotopic hepatocellular carcinoma xenograft nude mouse model
Authors: Guan Jian , Liu Mingyang , Li Xin , Zhou Liangrui , Dong Xueyu , Dai Wei , Xia Yu , Yang Tao , Guo Shaojuan , Li Xingqi , Han Yehua , Luo Yufeng 
Published: August 2021

Objective:

To explore the antitumor and potential off-target effects of systemically delivered cholesterol-conjugated
let-7a
mimics
(Chol-let-7a)
and control mimics
(Chol-miRCtrl)
on hepatocellular carcinoma
in vivo.

Methods:

The antitumor effects of two intravenous dosing regimens of
Chol-let-7a
on heptocellular carcinoma growth were compared using an orthotopic xenograft mouse model. Off-targets were analyzed with histopathological and ultrapathological features of heparenal tissue and cells in the
Chol-let-7a-, Chol-miRCtrl-,
and saline-treated (blank) xenograft mice and normal control mice. Then,
let-7
a abundance in orthotopic tumors, corresponding paracancerous hepatic tissue, and normal liver tissue from healthy nude mice was examined by reverse transcription-polymerase chain reaction. The distribution of
Chol-let-7a
and
Chol-miRCtrl in vivo
was examined by whole-animal imaging and frozen-sections observation. The experiments were approved by the Institutional Research Board of Peking Union Medical College Hospital.

Results:

Continuous treatment with
Chol-let-7a
resulted in tumors that were 35.86% and 40.02% the size of those in the
Chol-miRCtrl
and blank xenograft group (
P
< 0.01 and
P
< 0.01, respectively), while intermittent dosing with
Chol-let-7a
resulted in tumors that were 65.42% and 56.66% the size of those in the
Chol-miRCtrl
and the blank control group, respectively (
P
< 0.05 and
P
< 0.05). In addition, some histopathological and ultrapathological features were only observed after treatment with the two cholesterol-conjugated molecules, however mild with intermittent dosing
Chol-let-7a
treatment, such as diffuse sinusoidal dilation and edema, primarily around the centrolobular vein in heptic tissues; mild hypercellularity with dilated capillary lumens in the renal tissue; and some organelle abnormalities found in heptic and renal cells. Furthermore, whole-animal imaging showed that
Chol-let-7a
and
Chol-miRCtrl
were predominantly distributed in the liver, kidney, and bladder regions after injection, and that the concentration of
Chol-let-7a
and
Chol-miRCtrl
in the kidney and the bladder decreased much slowly in the xenograft animals, especially in the
Chol-miRCtrl
group. Finally, RT-PCR analysis showed that
let-7a
levels were significantly increased in Chol-let-7a-treated xenografts compared with
Chol-miRCtrl
group (
P
=0.003) and blank xenograft group (
P
=0.001); however, the level was only equivalent to 50.6% and 40.7% of that in paracancerous hepatic tissue and hepatic tissue in normal mice, respectively.

Conclusions:

Chol-let-7a,
administered either continuously or intermittently, showed effective antitumor efficacy.
Chol-let-7a
had some off-target effects, such as mild acute hepatitis-like inflammation and non-specific drug-induced kidney injury. The intermittent dosing regimen resulted in less damage than the continuous regimen, while maintaining relatively satisfactory antitumor efficacy, which could be useful for the investigation and possible clinical use of miRNA treatment regimens in the future.