Andrographolide Causes p53-independent HCC Cell Death through p62
Accumulation and Impaired DNA Damage Repair
Hepatocellular carcinoma (HCC) is a deadly cancer, with the dominant
driver mutations such as p53 yet undruggable. There is urgent demand to
search for novel agents and therapeutic targets for HCC treatment.
Andrographolide (Andro, a clinical-available anti-inflammation
phytochemical agent) could inhibit different types of cancer including
HCC, but the molecular mechanisms involved are yet unclear. The present
study thus determined how Andro mechanistically cause HCC cell death in
both in vitro and in vivo models. Andro dose- and time-dependently
induced HCC cell death but spared normal hepatocyte HL-7702.
Furthermore, Andro caused ROS-mediated DNA damage, which was critical
for cell death. Since p53 could induce G2/M cell cycle arrest, the
p53-present tumour cells were found to be more resistant to
Andro-induced cell death, compared to the p53-deficient cells. Notably,
Andro-induced p62 aggregation promoted proteasomal degradation of RAD51
and 53BP1, two essential proteins involved in DNA damage repair. As a
result, either silencing or knocking-out p62 promoted DNA damage repair
and consequently protected HCC cells from Andro- induced cell death.
Consistently, xenograft tumour developed by p62-knockout cells were more
resistant to Andro treatment. In addition, p53 and p62 were independent
with each other, since disrupting any one protein did not affect
expression of the other protein. Taken together, the present study may
shed light on repurposing Andro in the treatment of both p53-present and