Targeting ATAD3A-PINK1-mitophagy Axis Overcomes Chemoimmunotherapy Resistance By Redirecting PD-L1 To Mitochondria

Breast cancer is the most common malignant tumor in women.Triple-negative breast cancer(TNBC),classified by estrogen receptor(ER),progesterone receptor(PR)and human epidermal growth factor receptor-2(HER2)negativity,represents approximately 15% to 20%of all primary breast cancers.Due to lack of specific molecular targets for therapy and its aggressive biological behavior,the median overall survival of patients with TNBC is only around 13-to 18-months after metastasis.Therefore,TNBC treatment remains a great challenge.Clinical treatment option for triple-negative breast cancer is limited,utilizing the chemodrugs such as paclitaxel remains current standard therapeutic strategy for which.With the success of immune checkpoint inhibitor(ICI)therapy in various malignancies,PD-1/PD-L1 targeting strategies have been approved to treat patients with TNBC recently.However,the efficacy of PD-1/PD-L1 antibodies monotherapy is low,which in patients with PD-L1-positive tumors is less than 25%.Then,the chemo-drug nab-paclitaxel expected to enhance the efficacy of ICI is utilized to combine with anti-PD-L1 antibody atezolizumab in TNBC therapy.However,the combination therapy only results in a modest improvement in progression-free survival(PFS)and no statistical significance in improvement of overall survival(OS)of TNBC patients in IMpassion130 clinical trial.Another phase 3 IMpassion131 trial of combining paclitaxel with atezolizumab is more disappointing to show no benefit at its primary endpoint of PFS even in PD-L1-positive TNBC population.Therefore,it is in need of better understanding of the resistance mechanisms of ICI in combination with paclitaxel chemotherapy which remain unmet challenges.PD-L1 not only plays an important role in evasion from antitumor immunity,but also is a crucial target of ICI treatment.Multiple strategies,including transcriptional,translational or posttranslational downregulation of PD-L1,aim to overcome immunosuppressive status and enhance the efficacy of ICI.In addition to the modulation of protein levels,subcellular redistribution of PD-L1 is associated with T cell-mediated killing.These observations call for further investigation of linking subcellular redistribution pattern of PD-L1 to the efficacy of immunotherapy.Mitochondria,the power houses and metabolic centers,play essential role in multiple cellular biological processes.Additionally,mitochondria are also appreciated for regulating the responses of the immunity system.Besides,mitochondria-mediated cellular events support for immune cells development and activation.They also act as organelles responsible for signal transduction in innate immune responses.However,it is unclear whether mitochondria participate in chemoimmunotherapy response and efficacy of ICI therapy.In our immunotherapy cohorts,we discovered that chemoimmunotherapy response of TNBC patients was related to their subcellular redistribution of PD-L1.Tumor samples from responders showed significant localization of PD-L1 at mitochondria,while non-responders contained increased accumulation of it on tumor cell membrane instead of mitochondria.Furthermore,our results also revealed that ATAD3A-PINK1 mitophagy axis is in charge of regulating subcellular distribution pattern of PD-L1.Mechanistically,PD-L1 was recruited to mitochondria by mitophagy-initiating regulator PINK1 and was subsequently degraded in a mitophagy-dependent pathway.Importantly,chemo-drug paclitaxel encouraged ATAD3 A to restrain PINK1-dependent mitophagy,resulting in disrupted proteostasis network of PD-L1.Moreover,patients with high-ATAD3 A expressing tumors developed resistance to chemoimmunotherapy.Preclinical results revealed that inhibition of ATAD3 A reset a favorable antitumor immune microenvironment and improved the efficacy of combination therapy of ICI plus paclitaxel.The main results of this study are as follows:1.Mitochondrial redistribution of PD-L1 in patients with TNBC is associated with therapeutic responses to ICI.2.ATAD3 A level correlates with ICI resistance by preventing PD-L1 redistributing to mitochondria.3.ATAD3A-PINK1 mitophagy axis is involved in regulating mitochondrial redistribution and degradation pathway of PD-L1.4.Paclitaxel upregulates ATAD3 A to suppress PINK1-dependent mitophagy to promote immunotherapy resistance.5.ATAD3 A inhibition evokes a favorable tumor immune microenvironment.6.Inhibition of ATAD3 A improves the efficacy of ICI plus paclitaxel combination therapy.In summary,our results indicate that ATAD3 A serves not only as a chemoimmunotherapy resistant factor through preventing PD-L1 mitochondrial redistribution,but also as a promising target for increasing the therapeutic responses of ICI plus paclitaxel.