FIP200 Suppresses Immune Checkpoint Therapy Responses in Breast Cancers by Limiting AZI2/TBK1/IRF Signaling Independent of Its Canonical Autophagy Function

TBK1 is paradoxical in tumor development: a focus on the pathway mediating IFN-I expression

TANK-binding kinase 1 (TBK1) is a member of the IKK family and plays a crucial role in the activation of non-canonical NF-κB signaling and type I interferon responses. The aberrant activation of TBK1 contributes to the proliferation and survival of various types of tumor cells, particularly in specific mutational or tumorous contexts. Inhibitors targeting TBK1 are under development and application in both in vivo and in vitro settings, yet their clinical efficacy remains limited. Numerous literatures have shown that TBK1 can exhibit both tumor promoting and tumor inhibiting effects. TBK1 acts as a pivotal node within the innate immune pathway, mediating anti-tumor immunity through the activation of innate immune responses. Facilitating interferon-I (IFN-I) production represents a critical mechanism through which TBK1 bridges these processes. IFN has been shown to exert both beneficial and detrimental effects on tumor progression. Hence, the paradoxical role of TBK1 in tumor development may necessitate acknowledgment in light of its downstream IFN-I signaling cascade. In this paper, we review the signaling pathways mediated by TBK1 in various tumor contexts and summarize the dual roles of TBK1 and the TBK1-IFN pathways in both promoting and inhibiting tumor progression. Additionally, we highlight the significance of the TBK1-IFN pathway in clinical therapy, particularly in the context of immune response. We anticipate further advancements in the development of TBK1 inhibitors as part of novel cancer treatment strategies.

Role of Tumor Cell Intrinsic and Host Autophagy in Cancer

Macroautophagy (autophagy hereafter) is an intracellular nutrient scavenging pathway induced by starvation and other stressors whereby cellular components such as organelles are captured in double-membrane vesicles (autophagosomes), whereupon their contents are degraded through fusion with lysosomes. Two main purposes of autophagy are to recycle the intracellular breakdown products to sustain metabolism and survival during starvation and to eliminate damaged or excess cellular components to suppress inflammation and maintain homeostasis. In contrast to most normal cells and tissues in the fed state, tumor cells up-regulate autophagy to promote their growth, survival, and malignancy. This tumor-cell-autonomous autophagy supports elevated metabolic demand and suppresses tumoricidal activation of the innate and adaptive immune responses. Tumor-cell-nonautonomous (e.g., host) autophagy also supports tumor growth by maintaining essential tumor nutrients in the circulation and tumor microenvironment and by suppressing an antitumor immune response. In the setting of cancer therapy, autophagy is a resistance mechanism to chemotherapy, targeted therapy, and immunotherapy. Thus, tumor and host autophagy are protumorigenic and autophagy inhibition is being examined as a novel therapeutic approach to treat cancer.

Beyond self‑eating: Emerging autophagy‑independent functions for the autophagy molecules in cancer (Review)

Autophagy is a conserved catabolic process that controls organelle quality, removes misfolded or abnormally aggregated proteins and is part of the defense mechanisms against intracellular pathogens. Autophagy contributes to the suppression of tumor initiation by promoting genome stability, cellular integrity, redox balance and proteostasis. On the other hand, once a tumor is established, autophagy can support cancer cell survival and promote epithelial‑to‑mesenchymal transition. A growing number of molecules involved in autophagy have been identified. In addition to their key canonical activity, several of these molecules, such as ATG5, ATG12 and Beclin‑1, also exert autophagy‑independent functions in a variety of biological processes. The present review aimed to summarize autophagy‑independent functions of molecules of the autophagy machinery and how the activity of these molecules can influence signaling pathways that are deregulated in cancer progression.

Role of NuMA1 in breast cancer stem cells with implications for combination therapy of PIM1 and autophagy inhibition in triple negative breast cancer

Background

Nuclear mitotic apparatus protein 1 (NuMA1) is a cell cycle protein and upregulated in breast cancer. However, the role of NuMA1 in TNBC and its regulation in heterogenous populations remains elusive.

Methods

We performed CRISPR mediated deletion of NuMA1 in mouse TNBC cells, BF3M. FACS was utilized to isolate BCSCs, and bulk cells based on CD29 and CD61 markers. Cell viability, migration, and invasion ability of BCSCs and bulk cells was evaluated using MTT, wound healing and transwell invasion assays, respectively. In vivo mouse breast cancer and lung metastatic models were generated to evaluate the combination treatment of SMI-4a and Lys-o5 inhibitors.

Results

We identified that high expression of NuMA1 associated with poor survival of breast cancer patients. Further, human tissue microarray results depicted high expression of NuMA1 in TNBC relative to non-adjacent normal tissues. Therefore, we performed CRISPR mediated deletion of NuMA1 in a mouse mammary tumor cell line, BF3M and revealed that NuMA1 deletion reduced mammary tumorigenesis. We also showed that NuMA1 deletion reduced ALDH+ and CD29hiCD61+ breast cancer stem cells (BCSCs), indicating a role of NuMA1 in BCSCs. Further, sorted and characterized BCSCs from BF3M depicted reduced metastasis with NuMA1 KO cells. Moreover, we found that PIM1, an upstream kinase of NuMA1 plays a preferential role in maintenance of BCSCs associated phenotypes, but not in bulk cells. In contrast, PIM1 kinase inhibition in bulk cells depicted increased autophagy (FIP200). Therefore, we applied a combination treatment strategy of PIM1 and autophagy inhibition using SMI-4a and Lys05 respectively, showed higher efficacy against cell viability of both these populations and further reduced breast tumor formation and metastasis. Together, our study demonstrated NuMA1 as a potential therapeutic target and combination treatment using inhibitors for an upstream kinase PIM1 and autophagy inhibitors could be a potentially new therapeutic approach for TNBC.

Conclusions

Our study demonstrated that combination treatment of PIM1 inhibitor and autophagy inhibitor depicted reduced mammary tumorigenesis and metastasis by targeting NuMA1 in BCSCs and bulk cells of TNBC, demonstrating this combination treatment approach could be a potentially effective therapy for TNBC patients.

AZI2 mediates TBK1 activation at unresolved selective autophagy cargo receptor complexes with implications for CD8 T-cell infiltration in breast cancer

Most breast cancers do not respond to immune checkpoint inhibitors and there is an urgent need to identify novel sensitization strategies. Herein, we uncovered that activation of the TBK-IFN pathway that is mediated by the TBK1 adapter protein AZI2 is a potent strategy for this purpose. Our initial observations showed that RB1CC1 depletion leads to accumulation of AZI2, in puncta along with selective macroautophagy/autophagy cargo receptors, which are both required for TBK1 activation. Specifically, disrupting the selective autophagy function of RB1CC1 was sufficient to sustain AZI2 puncta accumulation and TBK1 activation. AZI2 then mediates downstream activation of DDX3X, increasing its interaction with IRF3 for transcription of pro-inflammatory chemokines. Consequently, we performed a screen to identify inhibitors that can induce the AZI2-TBK1 pathway, and this revealed Lys05 as a pharmacological agent that induced pro-inflammatory chemokine expression and CD8+ T cell infiltration into tumors. Overall, we have identified a distinct AZI2-TBK1-IFN signaling pathway that is responsive to selective autophagy blockade and can be activated to make breast cancers more immunogenic.Abbreviations: AZI2/NAP1: 5-azacytidine induced 2; CALCOCO2: calcium binding and coiled-coil domain 2; DDX3X: DEAD-box helicase 3 X-linked; FCCP: carbonyl cyanide p-triflouromethoxyphenylhydrazone; a protonophore that depolarizes the mitochondrial inner membrane; ICI: immune checkpoint inhibitor; IFN: interferon; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SQSTM1/p62: sequestosome 1; TAX1BP1: Tax1 binding protein 1; TBK1: TANK binding kinase 1.

In vivo CRISPR knockout screen identifies p47 as a suppressor of HER2+ breast cancer metastasis by regulating NEMO trafficking and autophagy flux

Autophagy is a conserved cellular process, and its dysfunction is implicated in cancer and other diseases. Here, we employ an in vivo CRISPR screen targeting genes implicated in the regulation of autophagy to identify the Nsfl1c gene encoding p47 as a suppressor of human epidermal growth factor receptor 2 (HER2)+ breast cancer metastasis. p47 ablation specifically increases metastasis without promoting primary mammary tumor growth. Analysis of human breast cancer patient databases and tissue samples indicates a correlation of lower p47 expression levels with metastasis and decreased survival. Mechanistic studies show that p47 functions in the repair of lysosomal damage for autophagy flux and in the endosomal trafficking of nuclear factor κB essential modulator for lysosomal degradation to promote metastasis. Our results demonstrate a role and mechanisms of p47 in the regulation of breast cancer metastasis. They highlight the potential to exploit p47 as a suppressor of metastasis through multiple pathways in HER2+ breast cancer cells.

Autophagy-amplifying nanoparticles evoke immunogenic cell death combined with anti-PD-1/PD-L1 for residual tumors immunotherapy after RFA

Incomplete radiofrequency ablation (IRFA) triggers mild protective autophagy in residual tumor cells and results in an immunosuppressive microenvironment. This accelerates the recurrence of residual tumors and causes resistance to anti-PD-1/PDL1 therapy, which bringing a great clinical challenge in residual tumors immunotherapy. Mild autophagy activation can promote cancer cell survival while further amplification of autophagy contributes to immunogenic cell death (ICD). To this regard, we constructed active targeting zeolitic imidazolate framework-8 (ZIF-8) nanoparticles (NPs) loaded with STF62247 or both STF62247 and BMS202, namely STF62247@ZIF-8/PEG-FA (SZP) or STF62247-BMS202@ZIF-8/PEG-FA (SBZP) NPs. We found that SZP NPs inhibited proliferation and stimulated apoptosis of residual tumor cells exposed to sublethal heat stress in an autophagy-dependent manner. Further results discovered that SZP NPs could amplify autophagy in residual tumor cells and evoke their ICD, which dramatically boosted the maturation of dendritic cells (DCs). Through vaccination experiments, we found for the first time that vaccination with heat + SZP treatment could efficiently suppress the growth of new tumors and establish long-term immunological memory. Furthermore, SBZP NPs could remarkably promote the ICD of residual tumor cells, obviously activate the anti-tumor immune microenvironment, and significantly inhibit the growth of residual tumors. Thus, amplified autophagy coupled with anti-PD-1/PDL1 therapy is potentially a novel strategy for treating residual tumors after IRFA.

Autophagy and autophagy-related pathways in cancer

Maintenance of protein homeostasis and organelle integrity and function is critical for cellular homeostasis and cell viability. Autophagy is the principal mechanism that mediates the delivery of various cellular cargoes to lysosomes for degradation and recycling. A myriad of studies demonstrate important protective roles for autophagy against disease. However, in cancer, seemingly opposing roles of autophagy are observed in the prevention of early tumour development versus the maintenance and metabolic adaptation of established and metastasizing tumours. Recent studies have addressed not only the tumour cell intrinsic functions of autophagy, but also the roles of autophagy in the tumour microenvironment and associated immune cells. In addition, various autophagy-related pathways have been described, which are distinct from classical autophagy, that utilize parts of the autophagic machinery and can potentially contribute to malignant disease. Growing evidence on how autophagy and related processes affect cancer development and progression has helped guide efforts to design anticancer treatments based on inhibition or promotion of autophagy. In this Review, we discuss and dissect these different functions of autophagy and autophagy-related processes during tumour development, maintenance and progression. We outline recent findings regarding the role of these processes in both the tumour cells and the tumour microenvironment and describe advances in therapy aimed at autophagy processes in cancer.

Regulation of RB1CC1/FIP200 stability and autophagy function by CREBBP-mediated acetylation in an intrinsically disordered region

RB1CC1/FIP200 is an essential macroautophagy/autophagy protein that plays an important role in a variety of biological and disease processes through its canonical autophagy-dependent and -independent functions. However, it remains largely unknown whether post-translational modifications could regulate RB1CC1 and its associated autophagy functions. Here, we report acetylation of several lysine residues of RB1CC1 by acetyltransferase CREBBP (CREB binding protein), with K276 as the major CREBBP acetylation site. K276 is also identified as a ubiquitination site by mass spectrometry, and acetylation at this site reduces ubiquitination of RB1CC1 to inhibit its ubiquitin-dependent degradation. We also find that RB1CC1 contains an N-terminal intrinsically disordered region (IDR) capable of forming liquid-liquid phase separation (LLPS) in vitro, which may drive formation of RB1CC1 puncta with LLPS properties in cells independent of SQSTM1/p62 and other autophagy receptors CALCOCO2/NDP52, NBR1, TAX1BP1 and OPTN. Mutational analysis shows that both K276 acetylation and the N-terminal IDR containing it are important for maintaining canonical autophagy function of RB1CC1 in breast cancer cells. Our findings demonstrate regulation of RB1CC1 by a new post-translational mechanism and suggest potential therapeutic application of inducing RB1CC1 degradation through blocking K276 acetylation in the treatment of cancer and other diseases.Abbreviations: Baf-A1: bafilomycin A1; CREBBP/CBP: CREB binding protein; CHX: cycloheximide; EP300/p300: E1A binding protein p300; FRAP: fluorescence recovery after photobleaching; HADCs: histone deacetylases; IDR: intrinsically disordered region; LLPS: liquid-liquid phase separation; KAT2A/GCN5: lysine acetyltransferase 2A; KAT2B/PCAF: lysine acetyltransferase 2B; KAT5/TIP60: lysine acetyltransferase 5; KAT8/MOF: lysine acetyltransferase 8; NAM: nicotinamide; PAS: phagophore assembly site; PEG-8000: polyethylene glycol 8000; RB1CC1/FIP200: RB1 inducible coiled-coil 1; TSA: trichostatin A.

Impact of context-dependent autophagy states on tumor progression

Macroautophagy is a cellular quality-control process that degrades proteins, protein aggregates and damaged organelles. Autophagy plays a fundamental role in cancer where, in the presence of stressors (for example, nutrient starvation, hypoxia, mechanical pressure), tumor cells activate it to degrade intracellular substrates and provide energy. Cell-autonomous autophagy in tumor cells and cell-nonautonomous autophagy in the tumor microenvironment and in the host converge on mechanisms that modulate metabolic fitness, DNA integrity and immune escape and, consequently, support tumor growth. In this Review, we will discuss insights into the tumor-modulating roles of autophagy in different contexts and reflect on how future studies using physiological culture systems may help to understand the complexity and open new therapeutic avenues.

Autophagy inhibition prevents lymphatic malformation progression to lymphangiosarcoma by decreasing osteopontin and Stat3 signaling

Lymphatic malformation (LM) is a vascular anomaly originating from lymphatic endothelial cells (ECs). While it mostly remains a benign disease, a fraction of LM patients progresses to malignant lymphangiosarcoma (LAS). However, very little is known about underlying mechanisms regulating LM malignant transformation to LAS. Here, we investigate the role of autophagy in LAS development by generating EC-specific conditional knockout of an essential autophagy gene Rb1cc1/FIP200 in Tsc1^iΔEC mouse model for human LAS. We find that Fip200 deletion blocked LM progression to LAS without affecting LM development. We further show that inhibiting autophagy by genetical ablation of FIP200, Atg5 or Atg7, significantly inhibited LAS tumor cell proliferation in vitro and tumorigenicity in vivo. Transcriptional profiling of autophagy-deficient tumor cells and additional mechanistic analysis determine that autophagy plays a role in regulating Osteopontin expression and its down-stream Jak/Stat3 signaling in tumor cell proliferation and tumorigenicity. Lastly, we show that specifically disrupting FIP200 canonical autophagy function by knocking-in FIP200-4A mutant allele in Tsc1^iΔEC mice blocked LM progression to LAS. These results demonstrate a role for autophagy in LAS development, suggesting new strategies for preventing and treating LAS.

Autophagy and tumorigenesis

Autophagy is a catabolic process that captures cellular waste and degrades them in the lysosome. The main functions of autophagy are quality control of cytosolic proteins and organelles, and intracellular recycling of nutrients in order to maintain cellular homeostasis. Autophagy is upregulated in many cancers to promote cell survival, proliferation, and metastasis. Both cell-autonomous autophagy (also known as tumor autophagy) and non-cell-autonomous autophagy (also known as host autophagy) support tumorigenesis through different mechanisms, including inhibition of p53 activation, sustaining redox homeostasis, maintenance of essential amino acids levels in order to support energy production and biosynthesis, and inhibition of antitumor immune responses. Therefore, autophagy may serve as a tumor-specific vulnerability and targeting autophagy could be a novel strategy in cancer treatment.

Regulation of autophagy fires up the cold tumor microenvironment to improve cancer immunotherapy

Immunotherapies, such as immune checkpoint inhibitors (ICIs) and chimeric antigen receptor (CAR) T cells, have revolutionized the treatment of patients with advanced and metastatic tumors resistant to traditional therapies. However, the immunosuppressed tumor microenvironment (TME) results in a weak response to immunotherapy. Therefore, to realize the full potential of immunotherapy and obstacle barriers, it is essential to explore how to convert cold TME to hot TME. Autophagy is a crucial cellular process that preserves cellular stability in the cellular components of the TME, contributing to the characterization of the immunosuppressive TME. Targeted autophagy ignites immunosuppressive TME by influencing antigen release, antigen presentation, antigen recognition, and immune cell trafficking, thereby enhancing the effectiveness of cancer immunotherapy and overcoming resistance to immunotherapy. In this review, we summarize the characteristics and components of TME, explore the mechanisms and functions of autophagy in the characterization and regulation of TME, and discuss autophagy-based therapies as adjuvant enhancers of immunotherapy to improve the effectiveness of immunotherapy.

TRIM27 cooperates with STK38L to inhibit ULK1-mediated autophagy and promote tumorigenesis

Autophagy represents a fundamental mechanism for maintaining cell survival and tissue homeostasis in response to physiological and pathological stress. Autophagy initiation converges on the FIP200-ATG13-ULK1 complex wherein the serine/threonine kinase ULK1 plays a central role. Here, we reveal that the E3 ubiquitin ligase TRIM27 functions as a negative regulatory component of the FIP200-ATG13-ULK1 complex. TRIM27 directly polyubiquitinates ULK1 at K568 and K571 sites with K48-linked ubiquitin chains, with proteasomal turnover maintaining control over basal ULK1 levels. However, during starvation-induced autophagy, TRIM27 catalyzes non-degradative K6- and K11-linked ubiquitination of the serine/threonine kinase 38-like (STK38L) kinase. In turn, STK38L ubiquitination promotes its activation and phosphorylation of ULK1 at Ser495, rendering ULK1 in a permissive state for TRIM27-mediated hyper-ubiquitination of ULK1. This cooperative mechanism serves to restrain the amplitude and duration of autophagy. Further evidence from mouse models shows that basal autophagy levels are increased in Trim27 knockout mice and that Trim27 differentially regulates tumorigenesis and metastasis. Our study identifies a key role of STK38L-TRIM27-ULK1 signaling axis in negatively controlling autophagy with relevance established in human breast cancer.

AZI2 positively regulates the induction of type I interferon in influenza-trigger pediatric pneumonia

5-azacytidine-induced protein 2 (AZI2) is known to have a crucial role in antiviral innate immunity. This study aims to explore the roles of AZI2 in influenza-trigger pediatric pneumonia and its molecular mechanism. qPCR and immunoblotting assays were used to determine the levels of target genes and proteins. The lung infection mouse model was established by using PR8 H1N1 virus in AZI2 germline knockout (AZI2-/-) and wide-type (WT) mice. In addition, HEK293T cell-based luciferase reporter assays were used to investigate the regulatory effects of AZI2 on type I interferon. Immune precipitation and immunofluorescence staining were used to evaluate the interactions between AZI2 and TANK binding kinase 1 (TBK1). We observed an elevation in the expressions of IFN-I and AZI2 in peripheral blood mononuclear cells from the pneumonia patients with mild symptoms. Interestingly, AZI2 deficiency deteriorated the influenza-induced pathological symptoms in the lung as well as reduced the survival rate. It was further showed that AZI2 positively regulated the expressions of type I interferon, inflammatory cytokines, and IFN production-related genes. The molecular mechanism data revealed that AZI2 regulated the interactions between TBK1 and TANK. In summary, AZI2 positively regulates type I interferon production in influenza-induced pediatric pneumonia by promoting the interactions between TBK1 and TANK.

Biglycan Promotes Cancer Stem Cell Properties, NFκB Signaling and Metastatic Potential in Breast Cancer Cells

Simple Summary

Breast cancer stem cells (BCSCs) are a small sub-population of cells within tumors with high metastatic potential. We identified biglycan (BGN) as a prospective molecular target in BCSCs that regulates the aggressive phenotypes of these cells. These findings establish a foundation for the development of therapeutics against BGN to eliminate BCSCs and prevent metastatic breast cancer.

Abstract

It is a major challenge to treat metastasis due to the presence of heterogenous BCSCs. Therefore, it is important to identify new molecular targets and their underlying molecular mechanisms in various BCSCs to improve treatment of breast cancer metastasis. Here, we performed RNA sequencing on two distinct co-existing BCSC populations, ALDH⁺ and CD29^hi CD61⁺ from PyMT mammary tumor cells and detected upregulation of biglycan (BGN) in these BCSCs. Genetic depletion of BGN reduced BCSC proportions and tumorsphere formation. Furthermore, BCSC associated aggressive traits such as migration and invasion were significantly reduced by depletion of BGN. Glycolytic and mitochondrial metabolic assays also revealed that BCSCs exhibited decreased metabolism upon loss of BGN. BCSCs showed decreased activation of the NFκB transcription factor, p65, and phospho-IκB levels upon BGN ablation, indicating regulation of NFκB pathway by BGN. To further support our data, we also characterized CD24⁻/CD44⁺ BCSCs from human luminal MCF-7 breast cancer cells. These CD24⁻/CD44⁺ BCSCs similarly exhibited reduced tumorigenic phenotypes, metabolism and attenuation of NFκB pathway after knockdown of BGN. Finally, loss of BGN in ALDH⁺ and CD29^hi CD61⁺ BCSCs showed decreased metastatic potential, suggesting BGN serves as an important therapeutic target in BCSCs for treating metastasis of breast cancer.

Non-canonical function of FIP200 is required for neural stem cell maintenance and differentiation by limiting TBK1 activation and p62 aggregate formation

FIP200 is an essential autophagy gene implicated in the regulation of postnatal neural progenitor/stem cells (NSCs). However, the contribution of FIP200's canonical-autophagy function and its non-canonical functions to postnatal NSC maintenance remains unclear. Utilizing a recently generated Fip200-4A allele that specifically impairs FIP200's canonical-autophagy function, we found that non-canonical functions of FIP200 was required for regulation of mouse NSC maintenance and neurogenesis in vivo. Ablating the non-canonical functions of FIP200, but not its autophagy function, increased TBK1 activation and p62 phosphorylation at S403 in NSCs. Phosphorylation of p62 was dependent on TBK1 kinase activity and increased the propensity of p62 aggregate formation specifically in FIP200-null NSCs. Accordingly, inhibition of TBK1 by amlexanox reduced p62 aggregates and restored NSC maintenance and differentiation in Fip200^hGFAP cKO mice. These results reveal a mechanism for the non-canonical functions of FIP200 in NSC maintenance and differentiation by limiting TBK1 activation and subsequently, p62 aggregate formation.

Crosstalk between autophagy inhibitors and endosome-related secretory pathways: a challenge for autophagy-based treatment of solid cancers

Autophagy is best known for its role in organelle and protein turnover, cell quality control, and metabolism. The autophagic machinery has, however, also adapted to enable protein trafficking and unconventional secretory pathways so that organelles (such as autophagosomes and multivesicular bodies) delivering cargo to lysosomes for degradation can change their mission from fusion with lysosomes to fusion with the plasma membrane, followed by secretion of the cargo from the cell. Some factors with key signalling functions do not enter the conventional secretory pathway but can be secreted in an autophagy-mediated manner.Positive clinical results of some autophagy inhibitors are encouraging. Nevertheless, it is becoming clear that autophagy inhibition, even within the same cancer type, can affect cancer progression differently. Even next-generation inhibitors of autophagy can have significant non-specific effects, such as impacts on endosome-related secretory pathways and secretion of extracellular vesicles (EVs). Many studies suggest that cancer cells release higher amounts of EVs compared to non-malignant cells, which makes the effect of autophagy inhibitors on EVs secretion highly important and attractive for anticancer therapy. In this review article, we discuss how different inhibitors of autophagy may influence the secretion of EVs and summarize the non-specific effects of autophagy inhibitors with a focus on endosome-related secretory pathways. Modulation of autophagy significantly impacts not only the quantity of EVs but also their content, which can have a deep impact on the resulting pro-tumourigenic or anticancer effect of autophagy inhibitors used in the antineoplastic treatment of solid cancers.

Role of autophagy on cancer immune escape

Autophagy is catabolic process by degradation of intracellular components in lysosome including proteins, lipids, and mitochondria in response to nutrient deficiency or stress such as hypoxia or chemotherapy. Increasing evidence suggests that autophagy could induce immune checkpoint proteins (PD-L1, MHC-I/II) degradation of cancer cells, which play an important role in regulating cancer cell immune escape. In addition to autophagic degradation of immune checkpoint proteins, autophagy induction in immune cells (macrophages, dendritic cells) manipulates antigen presentation and T cell activity. These reports suggest that autophagy could negatively or positively regulate cancer cell immune escape by immune checkpoint protein and antigens degradation, cytokines release, antigens generation. These controversial phenomenon of autophagy on cancer cell immune evasion may be derived from different experimental context or models. In addition, autophagy maybe exhibit a role in regulating host excessive immune response. So rational combination with autophagy could enhance the efficacy of cancer immunotherapy. In this review, the current progress of autophagy on cancer immune escape is discussed.

FIP200 controls the TBK1 activation threshold at SQSTM1/p62-positive condensates

The protein kinase TBK1 is a central regulator of innate immune responses and autophagy, and ablation of either function has been linked to neuroinflammatory or degenerative diseases. Autophagy is an intracellular process that recycles old or damaged proteins and organelles. In recent years, the TBK1-dependent regulation of autophagy pathways has been characterized. However, the autophagy-dependent regulation of TBK1 activity awaits further clarification. Here, we observed that TBK1 is recruited to SQSTM1/p62-containing aggregates via the selective autophagy receptor TAX1BP1. In these aggregates, TBK1 phosphorylates SQSTM1/p62 at serine 403 and thus presumably regulates the efficient engulfment and clearance of these structures. We found that TBK1 activation is strongly increased if FIP200, a component of the autophagy-inducing ULK1 complex, is not present or cannot bind to TAX1BP1. Given our collective findings, we hypothesize that FIP200 ensures the inducible activation of TBK1 at SQSTM1/p62 condensates.

Analysis of Tumor Microenvironment Characteristics in Bladder Cancer: Implications for Immune Checkpoint Inhibitor Therapy

The tumor microenvironment (TME) plays a crucial role in cancer progression and recent evidence has clarified its clinical significance in predicting outcomes and efficacy. However, there are no studies on the systematic analysis of TME characteristics in bladder cancer. In this study, we comprehensively evaluated the TME invasion pattern of bladder cancer in 1,889 patients, defined three different TME phenotypes, and found that different subtypes were associated with the clinical prognosis and pathological characteristics of bladder cancer. We further explored the signaling pathways, cancer-immunity cycle, copy number, and somatic mutation differences among the different subtypes and used the principal component analysis algorithm to calculate the immune cell (IC) score, a tool for comprehensive evaluation of TME. Univariate and multivariate Cox regression analyses showed that ICscore is a reliable and independent prognostic biomarker. In addition, the use of anti-programmed death-ligand (PD-L1) treatment cohort, receiver operating characteristic (ROC) curve, Tumor Immune Dysfunction and Exclusion (TIDE), Subnetwork Mappings in Alignment of Pathways (SubMAP), and other algorithms confirmed that ICscore is a reliable prognostic biomarker for immune checkpoint inhibitor response. Patients with higher ICscore showed a significant therapeutic advantage in immunotherapy. In conclusion, this study improves our understanding of the characteristics of TME infiltration in bladder cancer and provides guidance for more effective personalized immunotherapy strategies.

Autophagy Blockade Limits HER2+ Breast Cancer Tumorigenesis by Perturbing HER2 Trafficking and Promoting Release Via Small Extracellular Vesicles

Autophagy modulation is an emerging strategy for cancer therapy. By deleting an essential autophagy gene or disrupting its autophagy function, we determined a mechanism of HER2+ breast cancer tumorigenesis by directly regulating the oncogenic driver. Disruption of FIP200-mediated autophagy reduced HER2 expression on the tumor cell surface and abolished mammary tumorigenesis in MMTV-Neu mice. Decreased HER2 surface expression was due to trafficking from the Golgi to the endocytic pathways instead of the plasma membrane. Autophagy inhibition led to HER2 accumulation in early and late endosomes associated with intraluminal vesicles and released from tumor cells in small extracellular vesicles (sEVs). Increased HER2 release from sEVs correlated with reduced tumor cell surface levels. Blocking sEVs secretion rescued HER2 levels in tumor cells. Our results demonstrate a role for autophagy to promote tumorigenesis in HER2+ breast cancer. This suggests that blocking autophagy could supplement current anti-HER2 agents for treating the disease.

Role of FIP200 in inflammatory processes beyond its canonical autophagy function

FIP200 (RB1CC1) is a critical regulator of canonical macroautophagy and has also emerged as a crucial regulator of selective autophagy as well as inflammatory processes. The illumination of FIP200's role in autophagy at the molecular level has been accompanied by studies demonstrating the importance of its autophagy function in physiological processes in mammals and pathological contexts such as cancer. However, there is an increasing appreciation that most, if not all of the autophagy genes, also play a role in other processes such as LC3-associated phagocytosis, vesicle trafficking and protein secretion. Consequently, this has led to efforts in generating specific mutants of autophagy genes that are more amenable to dissecting their autophagy versus non-autophagy functions. In this aspect, we have generated a FIP200 knock-in mouse allele that is defective for canonical macroautophagy. This has revealed a canonical-autophagy-independent function of FIP200 that is responsible for limiting pro-inflammatory signaling. In this review, we will discuss FIP200's role in this process, the implications with regards to cancer immunotherapy and highlight key prospective avenues to specifically dissect the distinct functions of FIP200.