A dual-functional oncolytic adenovirus ZD55-aPD-L1 scFv armed with PD-L1 inhibitor potentiates its antitumor activity
Shengsheng Mei1, Shanshan Peng1, Eu Gene Vong1
1Department of Biochemistry, Cancer Institute of the Second Affiliated Hospital (Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education), School of Medicine, Zhejiang University, Hangzhou, China.
Background:
Clinical data indicate that a substantial portion of cancer patients, though eligible for immune checkpoint inhibitor (ICI) therapy, cannot fully benefit from ICI monotherapy due to the poor immunogenicity of tumors and lack of tumor-infiltrating lymphocytes within the 'cold' tumor microenvironment (TME). In addition to poor antibody penetrance into the TME, systemic delivery of ICIs is associated with immune-related adverse events (irAEs) among recipients, some of which are life-threatening. Oncolytic virotherapy is a potentially viable approach to improving the efficacy of ICI therapy because of their ability to selectively replicate and lyse tumor cells, release tumor-associated antigens (TAAs), induce inflammatory response and promote lymphocyte infiltration in tumors.
Methods:
A recombinant oncolytic adenoviruses (OAd), denoted ZD55-aPD-L1 scFv, which carried the expression cassette for anti-PD-L1 scFv was constructed by molecular cloning. Western blot and ELISA assay were performed to detect aPD-L1 scFv expression. Flow cytometry were used to analyse PD-L1 expression and count tumor cells. Co-culture assay of human peripheral blood mononuclear cells (PBMCs) with tumor cells in vitro and triple-negative breast cancer (TNBC) MDA-MB-231 tumor-bearing model in vivo were evaluated the antitumor effects of recombinant oncolytic adenoviruses ZD55-aPD-L1 scFv.
Results:
We found that cells infected with recombinant oncolytic adenovirus ZD55-aPD-L1 scFv can effectively express aPD-L1 scFv, which function similarly to its full-length anti-PD-L1 antibody. PBMCs have inherently very limited killing effect on tumor cells even with administration of anti-PD-L1 antibody as observed from our in vitro co-cultures. Treatment consisting of ZD55 alone or ZD55 combined with anti-PD-L1 antibody yielded mediocre antitumor efficacy in subsequent in vitro and in vivo investigations, but were all substantially surpassed by the synergistic antitumor effects observed with ZD55-aPD-L1 scFv treatment. We show that the concomitant direct oncolysis by the recombinant OAd and localized autocrine/paracrine interception of PD-1:PD-L1 checkpoint interaction mediated by ZD55-aPD-L1 scFv-infected cells is exceedingly superior to co-administration of ZD55 and anti-PD-L1 antibody in the human TNBC mice model.
Conclusions:
Our results provided evidence for the development of novel strategies, in this case an anti-PD-L1 scFv-armed OAd, to bolster immune responses to 'cold' tumors and to improve therapeutic responsiveness to ICIs.
Insights
A novel oncolytic adenovirus armed with anti-PD-L1 scFv effectively targets cold tumors. This combined therapy shows superior antitumor effects compared to traditional immune checkpoint inhibitors.
Area of Science:
- Oncolytic virotherapy
- Immunotherapy
- Cancer microenvironment modulation
Background:
- Many cancer patients are ineligible for immune checkpoint inhibitor (ICI) therapy due to cold tumors.
- Poor tumor immunogenicity and lymphocyte infiltration limit ICI efficacy.
- Systemic ICI delivery causes adverse events and has limited tumor penetration.
Purpose of the Study:
- To develop a novel oncolytic adenovirus (OAd) carrying an anti-PD-L1 single-chain variable fragment (scFv).
- To evaluate the antitumor efficacy of the engineered OAd (ZD55-aPD-L1 scFv).
- To assess the potential of this strategy to overcome resistance to ICI therapy in cold tumors.
Main Methods:
- Construction of recombinant oncolytic adenovirus ZD55-aPD-L1 scFv via molecular cloning.
- Verification of aPD-L1 scFv expression using Western blot and ELISA.
- Assessment of PD-L1 expression and tumor cell counts via flow cytometry.
- In vitro co-culture assays with human PBMCs and tumor cells.
- In vivo evaluation in a triple-negative breast cancer (TNBC) mouse model.
Main Results:
- ZD55-aPD-L1 scFv effectively expressed functional anti-PD-L1 scFv.
- Combined therapy with ZD55-aPD-L1 scFv demonstrated synergistic antitumor effects.
- This approach significantly outperformed monotherapy or combination of ZD55 and anti-PD-L1 antibody in vivo.
- Localized PD-1:PD-L1 checkpoint blockade by infected cells combined with oncolysis proved highly effective.
Conclusions:
- An anti-PD-L1 scFv-armed OAd is a promising strategy for 'cold' tumors.
- This approach can enhance anti-tumor immune responses.
- It offers a novel therapeutic avenue to improve responsiveness to immune checkpoint inhibitors.
