PD-L2 mediates tobacco smoking-induced recruitment of regulatory T cells via the RGMB/NFκB/CCL20 cascade.

Programmed cell death ligand 2 (PD-L2), a ligand for the receptor programmed cell death 1 (PD-1), has an identity of 34% with its twin ligand PD-L1 and exhibits higher binding affinity with PD-1 than PD-L1. However, the role of PD-L2 in non-small cell lung cancer (NSCLC) progression, especially tobacco-induced cancer progression, has not been fully understood. Here, we found that PD-L2 promoted tumor growth in murine models with recruitment of regulatory T cells (Tregs). In patients with NSCLC, PD-L2 expression level in tumor samples was higher than in counterpart normal controls and was positively associated with patients' response to anti-PD-1 treatment. Mechanismly, PD-L2 bound its receptor Repulsive guidance molecule B (RGMB) on cancer cells and activated extracellular signal-regulated kinase (Erk) and nuclear factor κB (NFκB), leading to increased production of chemokine CCL20, which recruited Tregs and contributed to NSCLC progression. Consistently, knockdown of RGMB or NFκB p65 inhibited PD-L2-induced CCL20 production, and silencing of PD-L2 repressed Treg recruitment by NSCLC cells. Furthermore, cigarette smoke and carcinogen benzo(a)pyrene (BaP) upregulated PD-L2 in lung epithelial cells via aryl hydrocarbon receptor (AhR)-mediated transcription activation, whose deficiency markedly suppressed BaP-induced PD-L2 upregulation. These results suggest that PD-L2 mediates tobacco-induced recruitment of Tregs via the RGMB/NFκB/CCL20 cascade, and targeting this pathway might have therapeutic potentials in NSCLC.

[Latest Findings on the Role of CD47 in Tumor Immune Evasion and Related Targeted Therapies].

CD47 is an immunoglobulin that is overexpressed on the surface of a variety of cancer cells. CD47 forms a signaling complex with signal regulatory protein alpha (SIRPα), prompting the escape of cancer cells from macrophage-mediated phagocytosis. In recent years, CD47 has been shown to be highly expressed in many types of solid tumors and is associated with poor prognosis in patients. More and more studies have shown that inhibition of the CD47-SIRPα signaling pathway can promote adaptive immune responses and enhance the phagocytosis of tumor cells by macrophages. Humanized anti-CD47 IgG4 monoclonal antibody has been studied in clinical trials for the treatment of a variety of advanced solid tumors and lymphomas, demonstrating a sound safety profile and achieving partial remission in some patients. In this review we discuss the structure and function of CD47 and the mechanism of CD47 regulation in tumors, summarize the research progress in therapeutic antibody drugs targeting CD47 and a bottleneck in research that targeted drugs are more prone to result in serious adverse effects, and evaluated the potential of the applying CD47-SIRPα signaling pathway in anti-cancer therapy.

Upregulation of wild-type p53 by small molecule-induced elevation of NQO1 in non-small cell lung cancer cells.

The tumor suppressor p53 is usually inactivated by somatic mutations in malignant neoplasms, and its reactivation represents an attractive therapeutic strategy for cancers. Here, we reported that a new quinolone compound RYL-687 significantly inhibited non-small cell lung cancer (NSCLC) cells which express wild type (wt) p53, in contract to its much weaker cytotoxicity on cells with mutant p53. RYL-687 upregulated p53 in cells with wt but not mutant p53, and ectopic expression of wt p53 significantly enhanced the anti-NSCLC activity of this compound. RYL-687 induced production of reactive oxygen species (ROS) and upregulation of Nrf2, leading to an elevation of the NAD(P)H:quinoneoxidoreductase-1 (NQO1) that can protect p53 by inhibiting its degradation by 20S proteasome. RYL-687 bound NQO1, facilitating the physical interaction between NQO1 and p53. NQO1 was required for RYL-687-induced p53 accumulation, because silencing of NQO1 by specific siRNA or an NQO1 inhibitor uridine, drastically suppressed RYL-687-induced p53 upregulation. Moreover, a RYL-687-related prodrug significantly inhibited tumor growth in NOD-SCID mice inoculated with NSCLC cells and in a wt p53-NSCLC patient-derived xenograft mouse model. These data indicate that targeting NQO1 is a rational strategy to reactivate p53, and RYL-687 as a p53 stabilizer bears therapeutic potentials in NSCLCs with wt p53.

Transcriptional regulation and small compound targeting of ACE2 in lung epithelial cells.

Angiotensin-converting enzyme 2 (ACE2) is the receptor of COVID-19 pathogen SARS-CoV-2, but the transcription factors (TFs) that regulate the expression of the gene encoding ACE2 (ACE2) have not been systematically dissected. In this study we evaluated TFs that control ACE2 expression, and screened for small molecule compounds that could modulate ACE2 expression to block SARS-CoV-2 from entry into lung epithelial cells. By searching the online datasets we found that 24 TFs might be ACE2 regulators with signal transducer and activator of transcription 3 (Stat3) as the most significant one. In human normal lung tissues, the expression of ACE2 was positively correlated with phosphorylated Stat3 (p-Stat3). We demonstrated that Stat3 bound ACE2 promoter, and controlled its expression in 16HBE cells stimulated with interleukin 6 (IL-6). To screen for medicinal compounds that could modulate ACE2 expression, we conducted luciferase assay using HLF cells transfected with ACE2 promoter-luciferase constructs. Among the 64 compounds tested, 6-O-angeloylplenolin (6-OAP), a sesquiterpene lactone in Chinese medicinal herb Centipeda minima (CM), represented the most potent ACE2 repressor. 6-OAP (2.5 µM) inhibited the interaction between Stat3 protein and ACE2 promoter, thus suppressed ACE2 transcription. 6-OAP (1.25-5 µM) and its parental medicinal herb CM (0.125%-0.5%) dose-dependently downregulated ACE2 in 16HBE and Beas-2B cells; similar results were observed in the lung tissues of mice following administration of 6-OAP or CM for one month. In addition, 6-OAP/CM dose-dependently reduced IL-6 production and downregulated chemokines including CXCL13 and CX3CL1 in 16HBE cells. Moreover, we found that 6-OAP/CM inhibited the entry of SARS-CoV-2 S protein pseudovirus into target cells. These results suggest that 6-OAP/CM are ACE2 inhibitors that may potentially protect lung epithelial cells from SARS-CoV-2 infection.

CXCL13 Signaling in the Tumor Microenvironment.

Chemokines have emerged as important players in tumorigenic process. An extensive body of literature generated over the last two or three decades strongly implicate abnormally activated or functionally disrupted chemokine signaling in liaising most-if not all-hallmark processes of cancer. It is well-known that chemokine signaling networks within the tumor microenvironment are highly versatile and context-dependent: exert both pro-tumoral and antitumoral activities. The C-X-C motif chemokine ligand 13 (CXCL13), and its cognate receptor CXCR5, represents an emerging example of chemokine signaling axes, which express the ability to modulate tumor growth and progression in either way. Collateral evidence indicate that CXCL13-CXCR5 axis may directly modulate tumor growth by inducing proliferation of cancer cells, as well as promoting invasive phenotypes and preventing their apoptosis. In addition, CXCL13-CXCR5 axis may also indirectly modulate tumor growth by regulating noncancerous cells, particularly the immune cells, within the tumor microenvironment. Here, we review the role of CXCL13, together with CXCR5, in the human tumor microenvironment. We first elaborate their patterns of expression, regulation, and biological functions in normal physiology. We then consider how their aberrant activity, as a result of differential overexpression or co-expression, may directly or indirectly modulate the growth of tumors through effects on both cancerous and noncancerous cells.

Marine Power on Cancer: Drugs, Lead Compounds, and Mechanisms.

Worldwide, 19.3 million new cancer cases and almost 10.0 million cancer deaths occur each year. Recently, much attention has been paid to the ocean, the largest biosphere of the earth that harbors a great many different organisms and natural products, to identify novel drugs and drug candidates to fight against malignant neoplasms. The marine compounds show potent anticancer activity in vitro and in vivo, and relatively few drugs have been approved by the U.S. Food and Drug Administration for the treatment of metastatic malignant lymphoma, breast cancer, or Hodgkin's disease. This review provides a summary of the anticancer effects and mechanisms of action of selected marine compounds, including cytarabine, eribulin, marizomib, plitidepsin, trabectedin, zalypsis, adcetris, and OKI-179. The future development of anticancer marine drugs requires innovative biochemical biology approaches and introduction of novel therapeutic targets, as well as efficient isolation and synthesis of marine-derived natural compounds and derivatives.

The red wine component ellagic acid induces autophagy and exhibits anti-lung cancer activity in vitro and in vivo.

Red wine consists of a large amount of compounds such as resveratrol, which exhibits chemopreventive and therapeutic effects against several types of cancers by targeting cancer driver molecules. In this study, we tested the anti-lung cancer activity of 11 red wine components and reported that a natural polyphenol compound ellagic acid (EA) inhibited lung cancer cell proliferation at an efficacy approximately equal to that of resveratrol. EA markedly increased the expression of the autophagosomal marker LC3-II as well as inactivation of the mechanistic target of rapamycin signalling pathway. EA elevated autophagy-associated cell death by down-regulating the expression of cancerous inhibitor of protein phosphatase 2A (CIP2A), and CIP2A overexpression attenuated EA-induced autophagy of lung cancer cells. Treating tumour-bearing mice with EA resulted in significant inhibition of tumour growth with suppression of CIP2A levels and increased autophagy. In addition, EA potentiated the inhibitory effects of the natural compound celastrol on lung cancer cells in vitro and in vivo by enhancing autophagy and down-regulating CIP2A. These findings indicate that EA may be a promising chemotherapeutic agent for lung cancer, and that the combination of EA and celastrol may have applicability for the treatment of this disease.

Multiregion sequencing reveals the intratumor heterogeneity of driver mutations in TP53-driven non-small cell lung cancer.

Intratumor heterogeneity (ITH) in non-small cell lung cancer (NSCLC) may account for resistance after a period of targeted therapies because drugs destroy only a portion of tumor cells. The recognition of ITH helps identify high-risk patients to make effective treatment decisions. However, ITH studies are confounded by interpatient heterogeneity in NSCLC and a large amount of passenger mutations. To address these issues, we recruited NSCLC patients carrying TP53 mutations and selected driver mutations within recurrently mutated genes in NSCLC. A total of 12-paired normal-tumor tissues were subjected to whole-genome/whole-exome sequencing. From these, 367 non-silent mutations were selected as driver mutations and deeply sequenced in 61 intratumoral microdissections. We identified a universal prevalence of heterogeneity in all 12 tumors, indicating branched evolution. Although TP53 mutations were observed in single biopsy of all 12 tumors, most tumors consist of both TP53 mutated and non-mutated cells in separate regions within the same tumor. This suggests the late molecular timing of the acquisition of TP53 mutations; therefore, the detection of TP53 mutations in a single biopsy may simply not reflect the early malignant potential. In addition, we identified regions of loss of heterozygosity surrounding TP53 and CDKN2A mutations in tumor 711, which also exhibited heterogeneity in different regional samples. Because the ITH of driver mutations likely has clinical consequences, further efforts are needed to limit the impact of ITH and to improve therapeutic efficiency, which will benefit NSCLC patients receiving targeted treatments.

Skp1: Implications in cancer and SCF-oriented anti-cancer drug discovery.

In the last decade, the ubiquitin proteasome system (UPS), in general, and E3 ubiquitin ligases, in particular, have emerged as valid drug targets for the development of novel anti-cancer therapeutics. Cullin RING Ligases (CRLs), which can be classified into eight groups (CRL1-8) and comprise approximately 200 members, represent the largest family of E3 ubiquitin ligases which facilitate the ubiquitination-derived proteasomal degradation of a myriad of functionally and structurally diverse substrates. S phase kinase-associated protein 1 (Skp1)-Cullin1-F-Box protein (SCF) complexes are the best characterized among CRLs, which play crucial roles in numerous cellular processes and physiological dysfunctions, such as in cancer biology. Currently, there is growing interest in developing SCF-targeting anti-cancer therapies for clinical application. Indeed, the research in this field has seen some progress in the form of cullin neddylation- and Skp2-inhibitors. However, it still remains an underdeveloped area and needs to design new strategies for developing improved form of therapy. In this review, we venture a novel strategy that rational pharmacological targeting of Skp1, a central regulator of SCF complexes, may provide a novel avenue for SCF-oriented anti-cancer therapy, expected: (i) to simultaneously address the critical roles that multiple SCF oncogenic complexes play in cancer biology, (ii) to selectively target cancer cells with minimal normal cell toxicity, and (iii) to offer multiple chemical series, via therapeutic interventions at the Skp1 binding interfaces in SCF complex, thereby maximizing chances of success for drug discovery. In addition, we also discuss the challenges that might be posed regarding rational pharmacological interventions against Skp1.

Celastrol induces proteasomal degradation of FANCD2 to sensitize lung cancer cells to DNA crosslinking agents.

The Fanconi anemia (FA) pathway plays a key role in interstrand crosslink (ICL) repair and maintenance of the genomic stability, while inhibition of this pathway may sensitize cancer cells to DNA ICL agents and ionizing radiation (IR). The active FA core complex acts as an E3 ligase to monoubiquitinate FANCD2, which is a functional readout of an activated FA pathway. In the present study, we aimed to identify FANCD2-targeting agents, and found that the natural compound celastrol induced degradation of FANCD2 through the ubiquitin-proteasome pathway. We demonstrated that celastrol downregulated the basal and DNA damaging agent-induced monoubiquitination of FANCD2, followed by proteolytic degradation of the substrate. Furthermore, celastrol treatment abrogated the G2 checkpoint induced by IR, and enhanced the ICL agent-induced DNA damage and inhibitory effects on lung cancer cells through depletion of FANCD2. These results indicate that celastrol is a FANCD2 inhibitor that could interfere with the monoubiquitination and protein stability of FANCD2, providing a novel opportunity to develop FA pathway inhibitor and combinational therapy for malignant neoplasms.

Bortezomib interferes with C-KIT processing and transforms the t(8;21)-generated fusion proteins into tumor-suppressing fragments in leukemia cells.

The boronic acid dipeptide bortezomib inhibits the chymotrypsin-like activity of the 26S proteasome and shows significant therapeutic efficacy in multiple myeloma. However, recent studies suggest that bortezomib may have more complex mechanisms of action in treating cancer. We report here that the endocytosis and lysosomal degradation of the receptor tyrosine kinase C-KIT are required for bortezomib- but not tyrosine kinase inhibitor imatinib-caused apoptosis of t(8;21) leukemia and gastrointestinal stromal tumor cells, suggesting that C-KIT may recruit an apoptosis initiator. We show that C-KIT binds and phosphorylates heat shock protein 90ß (Hsp90ß), which sequestrates apoptotic protease activating factor 1 (Apaf-1). Bortezomib dephosphorylates pHsp90ß and releases Apaf-1. Although the activated caspase-3 is not sufficient to cause marked apoptosis, it cleaves the t(8;21) generated acute myeloid leukemia 1-eight twenty one (AML1-ETO) and AML1-ETO9a fusion proteins, with production of cleavage fragments that perturb the functions of the parental oncoproteins and further contribute to apoptosis. Notably, bortezomib exerts potent therapeutic efficacy in mice bearing AML1-ETO9a-driven leukemia. These data show that C-KIT-pHsp90ß-Apaf-1 cascade is critical for some malignant cells to evade apoptosis, and the clinical therapeutic potentials of bortezomib in C-KIT-driven neoplasms should be further explored.

Cancerous inhibitor of PP2A is targeted by natural compound celastrol for degradation in non-small-cell lung cancer.

Celastrol binds CIP2A and enhances CIP2A-CHIP interaction, leading to ubiquitination/degradation of CIP2A and inhibition of lung cancer cells in vitro and in vivo. Celastrol potentiates cisplatin's efficacy by suppressing the CIP2A-Akt pathway, and therefore CIP2A inhibitors may represent novel therapeutics for cancer.

Identification of novel bivalent mimetics of annonaceous acetogenins via a scaffold-hopping strategy.

A series of novel bivalent mimetics of annonaceous acetogenins have been designed, synthesized, and evaluated. Among these, compound 7 bearing a homopiperazine ring in the middle region exhibited more potent growth inhibitory activity and higher selectivity against cancer cells over normal cells by comparison with AA005. This work indicates that modification of the middle piperazine ring is a useful optimizing tool for the simplified acetogenin mimetics.

Oncogenic functions and therapeutic potentials of targeted inhibition of SMARCAL1 in small cell lung cancer.

Small cell lung cancer (SCLC) is a recalcitrant cancer characterized by high frequency loss-of-function mutations in tumor suppressors with a lack of targeted therapy due to absence of high frequency gain-of-function abnormalities in oncogenes. SMARCAL1 is a member of the ATP-dependent chromatin remodeling protein SNF2 family that plays critical roles in DNA damage repair and genome stability maintenance. Here, we showed that SMARCAL1 was overexpressed in SCLC patient samples and was inversely associated with overall survival of the patients. SMARCAL1 was required for SCLC cell proliferation and genome integrity. Mass spectrometry revealed that PAR6B was a downstream SMARCAL1 signal molecule which rescued inhibitory effects caused by silencing of SMARCAL1. By screening of 36 FDA-approved clinically available agents related to DNA damage repair, we found that an aza-anthracenedione, pixantrone, was a potent SMARCAL1 inhibitor which suppressed the expression of SMARCAL1 and PAR6B at protein level. Pixantrone caused DNA damage and exhibited inhibitory effects on SCLC cells in vitro and in a patient-derived xenograft mouse model. These results indicated that SMARCAL1 functions as an oncogene in SCLC, and pixantrone as a SMARCAL1 inhibitor bears therapeutic potentials in this deadly disease.

Centipeda minima and 6-O-angeloylplenolin enhance the efficacy of immune checkpoint inhibitors in non-small cell lung cancer.

BACKGROUND: Chemotherapeutic agents including cisplatin, gemcitabine, and pemetrexed, significantly enhance the efficacy of immune checkpoint inhibitors (ICIs) in non-small cell lung cancer (NSCLC) by increasing PD-L1 expression and potentiating T cell cytotoxicity. However, the low response rate and adverse effects limit the application of chemotherapy/ICI combinations in patients. METHODS: We screened for medicinal herbs that could perturb PD-L1 expression and enhance T cell cytotoxicity in the presence of anti-PD-L1 antibody, and investigated the underlying mechanisms. RESULTS: We found that the aqueous extracts of Centipeda minima (CM) significantly enhanced the cancer cell-killing activity and granzyme B expression level of CD8+ T cells, in the presence of anti-PD-L1 antibody. Both CM and its active component 6-O-angeloylplenolin (6-OAP) upregulated PD-L1 expression by suppressing GSK-3ß-ß-TRCP-mediated ubiquitination and degradation. CM and 6-OAP significantly enhanced ICI-induced reduction of tumor burden and prolongation of overall survival of mice bearing NSCLC cells, accompanied by upregulation of PD-L1 and increase of CD8+ T cell infiltration. CM also exhibited anti-NSCLC activity in cells and in a patient-derived xenograft mouse model. CONCLUSIONS: These data demonstrated that the induced expression of PD-L1 and enhancement of CD8+ T cell cytotoxicity underlay the beneficial effects of 6-OAP-rich CM in NSCLCs, providing a clinically available and safe medicinal herb for combined use with ICIs to treat this deadly disease.

CIP2A induces PKM2 tetramer formation and oxidative phosphorylation in non-small cell lung cancer.

Tumor cells are usually considered defective in mitochondrial respiration, but human non-small cell lung cancer (NSCLC) tumor tissues are shown to have enhanced glucose oxidation relative to adjacent benign lung. Here, we reported that oncoprotein cancerous inhibitor of protein phosphatase 2A (CIP2A) inhibited glycolysis and promoted oxidative metabolism in NSCLC cells. CIP2A bound to pyruvate kinase M2 (PKM2) and induced the formation of PKM2 tetramer, with serine 287 as a novel phosphorylation site essential for PKM2 dimer-tetramer switching. CIP2A redirected PKM2 to mitochondrion, leading to upregulation of Bcl2 via phosphorylating Bcl2 at threonine 69. Clinically, CIP2A level in tumor tissues was positively correlated with the level of phosphorylated PKM2 S287. CIP2A-targeting compounds synergized with glycolysis inhibitor in suppressing cell proliferation in vitro and in vivo. These results indicated that CIP2A facilitates oxidative phosphorylation by promoting tetrameric PKM2 formation, and targeting CIP2A and glycolysis exhibits therapeutic potentials in NSCLC.

Potential molecular targets for inhibiting bone invasion by oral squamous cell carcinoma: a review of mechanisms.

Bone invasion is a common characteristic of oral squamous cell carcinoma (OSCC), with adverse affects on patient functionality and survival. Recent studies suggest that it is osteoclasts, rather than malignant keratinocytes themselves, which play the major role in facilitating the entry of the tumour into bone, and its progression within bone. Osteoclasts respond to a variety of local signalling pathways, initiated by products of the malignant epithelial cells. In the present review, we firstly introduce the clinical patterns of bone invasion, and then summarise these signalling pathways and their diverse roles in sequential phases of bone invasion. We also review current researches regarding the incidence and mechanisms of distant metastases to bone, and explain briefly the concept of epithelial-mesenchymal transition, which may generate cancer stem cells and initiate the bone invasion. Finally, we discuss more briefly approaches to the diagnosis and management of OSCC patients with bone invasion. With all these studies and some recent discoveries in our own laboratory, an enhanced understanding of bone invasion will be achieved, which should indicate potential molecular targets for future biotherapies.

Small compound bigelovin exerts inhibitory effects and triggers proteolysis of E2F1 in multiple myeloma cells.

Multiple myeloma (MM) is a currently incurable blood cancer. Here we tested the effects of a small compound bigelovin on MM cells, and reported that it caused cell cycle arrest and subsequently induced apoptosis. Bigelovin triggered proteolysis of E2F1, which could be inhibited by caspase inhibitor. To investigate the clinical relevance, the expression of E2F1 in MM specimens was tested, and the results showed that E2F1 was overexpressed in 25-57% of MM patients and was associated with higher International Staging System (ISS) stage. These results suggest that E2F1 may be important for MM pathogenesis, and bigelovin could serve as a lead compound for the development of E2F1 inhibitor.

From an old remedy to a magic bullet: molecular mechanisms underlying the therapeutic effects of arsenic in fighting leukemia.

Arsenic had been used in treating malignancies from the 18th to mid-20th century. In the past 3 decades, arsenic was revived and shown to be able to induce complete remission and to achieve, when combined with all-trans retinoic acid and chemotherapy, a 5-year overall survival of 90% in patients with acute promyelocytic leukemia driven by the t(15;17) translocation-generated promyelocytic leukemia-retinoic acid receptor α (PML-RARα) fusion. Molecularly, arsenic binds thiol residues and induces the formation of reactive oxygen species, thus affecting numerous signaling pathways. Interestingly, arsenic directly binds the C3HC4 zinc finger motif in the RBCC domain of PML and PML-RARα, induces their homodimerization and multimerization, and enhances their interaction with the SUMO E2 conjugase Ubc9, facilitating subsequent sumoylation/ubiquitination and proteasomal degradation. Arsenic-caused intermolecular disulfide formation in PML also contributes to PML-multimerization. All-trans retinoic acid, which targets PML-RARα for degradation through its RARα moiety, synergizes with arsenic in eliminating leukemia-initiating cells. Arsenic perturbs a number of proteins involved in other hematologic malignancies, including chronic myeloid leukemia and adult T-cell leukemia/lymphoma, whereby it may bring new therapeutic benefits. The successful revival of arsenic in acute promyelocytic leukemia, together with modern mechanistic studies, has thus allowed a new paradigm to emerge in translational medicine.

Air pollution, EGFR mutation, and cancer initiation.

Swanton et al.1 find that PM2.5 exposure is associated with EGFR/KRAS-driven lung cancer incidence. PM2.5 increases EGFR pre-mutated alveolar type II cell progenitor function and tumorigenic activity through interstitial macrophage-secreted IL-1ß, providing potential prevention approaches to inhibit cancer initiation.