2017Joint Usage and Research Report
Title of Research Project

Elucidation of the chemoresistance mechanism of ANT2 and its
therapeutic potential in cancer chemotherapy

ApplicantVisiting

Institution

Harbin Institute of Technology, China

Job title

Postdocand name

Kai LiName

Kai Liresearcher
Purpose of the Research Project

It has been reported that IFNs play a multifaceted role in the induction of(approx. 250 words)

antitumor immunity. In addition to their direct cytotoxic effects on tumor,
targeting low doses of type I IFNs to the tumor microenvironment also
promotes the maturation and antigen presentation of DCs and boosts
endogenous NK or CD8+ T cell-mediated antitumor immune responses.
Endoplasmic-reticulum (ER)-membrane protein STING is thought tofunction as an adaptor protein, which links upstream DNA sensors todownstream IRF-3 and NF-κB pathway activation. Recent studies havedemonstrated that STING plays a key role in antitumor immune response.
After transplantation of immunogenic tumors in STING-deficient mice,the tumors grow more rapidly than transplantation in wild-type mice orTRIF-deficient mice. Spontaneous CD8+ T cell priming against tumors
was also defective in mice lacking STING, but not in those lacking TLRs,
MyD88 or MAVS, suggesting cytosolic DNA sensing pathway is involvedin controlling tumor growth. Results from our ongoing project showthat ANT2 has an inhibitory function on cGAS-STING signaling
pathway. Therefore, we hypothesize that ANT2 may negatively
regulate STING-mediated antitumor response during cancer
chemotherapy, targeting ANT2 to boost antitumor activity ofSTING will hopefully provide a promising therapeutic strategy
against tumor progression.
In conclusion, the main purposes of the collaboration are:1.

Elucidating

theroleANT2andSTING

inchemotherapy-induced cell death.
2. Investigating the detail mechanism of ANT2 negatively
regulating SING pathway.
3. Understanding the role of ANT2 in chemoresistance and its
relationship with innate immune signaling pathway.
Development of the Research

Research Project

Project and Results

The role of STING and its role in innate immune response is(approx.. 850 words)

well characterized. And recent works also reported that activationof STING by tumor-derived DNA for IFNs production and DC-mediatedcross-priming is critical for generating adaptive antitumor immunity. In
additional, activation of STING pathway results in production of IFNs forinducing ISGs to prompt cell death, it also can cause cell death via
IFNs-independent manner, which is through STING-mediated IRF-3
interaction with Bcl-2-associated X protein (Bax) on mitochondria toactivate the mitochondrial apoptosis pathway dependent on caspases 9and 3. Therefore, triggering of STING signaling can directly induce
cancer cell death and may provide a new cancer therapy option. However,it has been demonstrated that apoptotic caspases suppress the activation ofSTING pathway. Hence, a feedback regulation between STING andapoptosis signaling pathway may exist; trying to release this inhibitory
effect of apoptotic caspases on STING may enhance the anticancer
activity of STING. ANT2 (Adenine Nucleotide Translocase-2) is a
mitochondrial protein that facilitates the exchange of ADP and ATP acrossthe mitochondrial membrane. Previous studies have indicated that theexpression of ANT2 is upregulated in several types of cancer, knockdownof ANT2 showed decreased cancer cell migration/invasion and enhanced
sensitivity of cancer cells to anticancer drugs. These results suggested thatANT2 is a key player in tumor progression and a promising target forcancer therapy. However, the tumor-supportive mechanisms of ANT2 arestill poorly understood. Our previous study indicated that ANT2 is a novel
repressor of STING signaling pathway. Therefore, the goal of this projectis to investigate the role of STING repressor-ANT2 in chemotherapy
induced cell death and clarify the novel chemoresistance mechanismof ANT2.
Progress and results
1) By using in vitro cell model and in vivo mice model, we foundthatchemotherapy(Doxorubicin,CisplatinandEtoposide)treatment induces the expression of interferons(IFNs) andcytokines (by using qRT-PCR and ELISA detection), and thisinduction is dependent on cGAS-STING signaling pathway (byusing cGAS/STING knockdown cell line or STING KO mice). An
elevatus expression of interferons(IFNs) and cytokines areobserved in ANT2 knock out cells or mice upon chemotherapy
treatment and cause a more serious cell death compare withwild type. ANT2 is induced by chemotherapy treatment in vitro
and in vivo (not only mRNA level but also protein level) but thisinduction is not dependent on STING pathway and also p53

pathway. ANT2 interacts with STING and represses its
downstrean signaling transduction.
2) A high impact journal manuscript “ANT2 functions as anegative regulator in the DNA sensing pathway via STING andprotects hepatocytes from chemotherapy-driven liver damage”
Kai Li, Seiichi Sato, Kozo Ishikawa, Chikashi Obuse, Naohiro
Terada, Akinori Takaoka et al., 2018 is in preparation.
Remaining Work and Expected Results
1) The mechanism of ANT2 induction upon chemotherpy is stillunknow. To fullly understand this, we will analyze the promoterof ANT2 and identify the factors involved in the induction ofANT2.
2) To fully understand the mechanism of ANT2 repressing
STING signaling pathway and STING-mediated innate immune
response, we will clarify the role ANT2 on STING-cGAMP
interaction. Due to the interaction site of ANT2 with STING isoverlap with cGAMP binding site, therefore, we specurate that
ANT2 may inhibit cGAMP binds to STING.
Publication【Conference, symposium, workshop etc.】*Enter the names of conferenceor journal and its vol. No. where
the above work was presented.
【Journals】