Established Tumors Research Articles

From the Editor’s Desk...

From the Editor’s Desk...

Augmentation of antitumor function of tumor-infiltrating lymphocytes against triple-negative breast cancer by PD-1 blockade.

T-cell-based immunotherapy and immune checkpoint blockade have been successfully used to treat several human solid cancers. The present study attempted to investigate the feasibility and efficacy of the antitumor effect of adoptive cell therapy along with programmed cell death protein 1 (PD-1) inhibitor on triple-negative breast cancer (TNBC). Tumor infiltration lymphocytes (TILs) from TNBC mouse tumor tissues were isolated and expanded, and TILs for adoptive cell therapy (TILs-ACT) were applied in combination with a PD-1 inhibitor to the TNBC mouse model. The pre- and post-therapy antitumor efficacy, cytokine secretion, and pathological changes were assessed both in vitro and in vivo. We found that TILs exhibited higher IFN-γ and TNF-α secretion than conventional T cells. The TILs-ACT combined with PD-1 inhibitor promoted active T-cell infiltration into the tumor tissue and exerted a strong antitumor effect in an in vivo model. Additionally, the strategy could downregulate the expression of inhibitory marker PD-1 on TILs. In conclusion, PD-1 blockade regulated T-cell exhaustion that synergized with adoptive TIL transfer immunotherapy, leading to eradication of established TNBC tumors. These findings might be useful in developing a feasible and effective therapeutic approach for TNBC.

Targeting CD70 in cutaneous T-cell lymphoma using an antibody-drug conjugate in patient-derived xenograft models

AbstractCD70 is a member of the tumor necrosis factor receptor superfamily. Emerging data indicate that CD70 may be a suitable target for various malignancies. We investigated the expression of CD70 in cutaneous and systemic T-cell lymphomas and conducted preclinical studies of SGN-CD70A, a CD70-directed antibody-drug conjugate (ADC), using patient-derived xenograft cutaneous T-cell lymphoma (CTCL PDX) models. CD70 expression was examined by immunohistochemical (IHC) stains in 49 diagnostic specimens of T-cell lymphomas. The activities of SGN-CD70A in growth inhibition and apoptosis induction were examined in CTCL cell lines and primary CTCL tumor cells. Using previously established CTCL PDXs, we conducted a dose-finding trial followed by a phase 2-like trial to evaluate the optimal dosing and the efficacy of SGN-CD70A in tumor-bearing PDX animals. The therapeutic efficacy of SGN-CD70A was measured by tumor-associated cell-free DNA (cfDNA) and survival of treated PDXs. We found that CD70 is highly expressed in T-cell lymphomas, especially in CTCL. SGN-CD70A inhibited cell growth and induced apoptosis in CD70-expressing CTCL cell lines and primary tumors cells. Additionally, SGN-CD70A at 100 μg/kg and 300 μg/kg prolonged the survival of PDXs in a dose-dependent manner. Finally, treatment with 3 doses of SGN-CD70A at 300 μg/kg was superior to a single-dose treatment in survival prolongation (median survival: 111 days vs 39 days; P = .017). Most importantly, multiple dosing of SGN-CD70A induced complete eradication of established tumors in PDXs measured by cfDNA. Our results demonstrated marked antitumor activity of SGN-CD70A in CTCL PDXs, providing compelling support for its clinical investigation.

Established Tumour Biomarkers Predict Cardiovascular Events and Mortality in the General Population.

Introduction: Several lines of evidence reveal that cardiovascular disease (CVD) and cancer share similar common pathological milieus. The prevalence of the two diseases is growing as the population ages and the burden of shared risk factors increases. In this respect, we hypothesise that tumour biomarkers can be potential predictors of CVD outcomes in the general population.Methods: We measured six tumour biomarkers (AFP, CA125, CA15-3, CA19-9, CEA and CYFRA 21-1) and determined their predictive value for CVD in the Prevention of Renal and Vascular End-stage Disease (PREVEND) study. A total of 8,592 subjects were enrolled in the study.Results: The levels of CEA significantly predicted CV morbidity and mortality, with hazard ratios (HRs) of HR 1.28 (95% CI 1.08–1.53), respectively. Two biomarkers (CA15-3 and CEA) showed statistical significance in predicting all-cause mortality, with HRs 1.58 (95% CI 1.18–2.12) and HR 1.60 (95% CI 1.30–1.96), when adjusted for shared risk factors and prevalent CVD. Furthermore, biomarkers seem to be sex specific. CYFRA 21-1 presented as an independent predictor of CV morbidity and mortality in female, but not in male gender, with HR 1.82 (95% CI 1.40–2.35). When it comes to all-cause mortality, both CYFRA and CEA show statistical significance in male gender, with HR 1.64 (95% CI 1.28–3.12) and HR 1.55 (95% CI 1.18–2.02), while only CEA showed statistical significance in female gender, with HR 1.64 (95% CI 1.20–2.24). Lastly, CA15-3 and CEA strongly predicted CV mortality with HR 3.01 (95% CI 1.70–5.32) and HR 1.82 (95% CI 1.30–2.56). On another hand, CA 15-3 also presented as an independent predictor of heart failure (HF) with HR 1.67 (95% CI 1.15–2.42).Conclusion: Several tumour biomarkers demonstrated independent prognostic value for CV events and all-cause mortality in a large cohort from the general population. These findings support the notion that CVD and cancer are associated with similar pathological milieus.

HSP90 Inhibition Synergizes with Cisplatin to Eliminate Basal-like Pancreatic Ductal Adenocarcinoma Cells.

Simple SummaryPancreatic cancer is currently difficult to treat, but the drug cisplatin represents one of the most important therapeutic options. We find that cells derived from this cancer fall into two classes regarding their sensitivity towards cisplatin, and we observe that cells with high expression levels of GATA6 and microRNA 200 are mostly sensitive. However, those cells that respond poorly to cisplatin can be sensitized by drugs that inhibit HSP90, a protein that helps other proteins to fold properly. This was also found in a mouse model of pancreatic cancer. Our results suggest that the combination of cisplatin with HSP90-inhibitory drugs might improve the treatment of pancreatic cancer.To improve the treatment of pancreatic ductal adenocarcinoma (PDAC), a promising strategy consists of personalized chemotherapy based on gene expression profiles. Investigating a panel of PDAC-derived human cell lines, we found that their sensitivities towards cisplatin fall in two distinct classes. The platinum-sensitive class is characterized by the expression of GATA6, miRNA-200a, and miRNA-200b, which might be developable as predictive biomarkers. In the case of resistant PDAC cells, we identified a synergism of cisplatin with HSP90 inhibitors. Mechanistic explanations of this synergy include the degradation of Fanconi anemia pathway factors upon HSP90 inhibition. Treatment with the drug combination resulted in increased DNA damage and chromosome fragmentation, as we have reported previously for ovarian cancer cells. On top of this, HSP90 inhibition also enhanced the accumulation of DNA-bound platinum. We next investigated an orthotopic syngeneic animal model consisting of tumors arising from KPC cells (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre, C57/BL6 genetic background). Here again, when treating established tumors, the combination of cisplatin with the HSP90 inhibitor onalespib was highly effective and almost completely prevented further tumor growth. We propose that the combination of platinum drugs and HSP90 inhibitors might be worth testing in the clinics for the treatment of cisplatin-resistant PDACs.

Ephrin Receptors (Ephs) Expression in Thymic Epithelial Tumors: Prognostic Implications and Future Therapeutic Approaches.

Ephrin receptors (Ephs) are receptor tyrosine kinases (RTKs) implicated in tissue development and homeostasis, and they are aberrantly expressed in tumors. Here, immunohistochemical Eph type-A and -B expression in thymic epithelial tumors (TETs) was assessed and correlated with clinicopathological parameters. Tissue microarrays from 98 TETs were stained for EphA1, -A2, -A4 -A6, -B1, -B2, -B4 and -B6. The relationship between neoplastic and lymphoid cell immunoreactivity score (H-score), histopathological parameters (Pearson’s test) and survival of 35 patients (Mantel-Cox model) was explored. Epithelial-rich subtypes showed higher EphA6 cytoplasmic H-score (B2/B3, carcinoma) (p < 0.001) and stronger EphA4 H-score (B3, carcinoma) (p = 0.011). The immature T-cells, especially in subtypes AB/B1, had higher EphB6 H-score than carcinoma-associated mature lymphocytes (p < 0.001); carcinomas had higher lymphocytic EphB1 H-score (p = 0.026). Higher lymphocytic and lower epithelial EphB6 H-score correlated with Masaoka stage ≤II (p = 0.043, p = 0.010, respectively). All cases showed variable epithelial and lymphocytic EphA2 expression, but clinicopathological associations were not reached. Our study confirmed that Eph type-A and -B expression in TETs is associated with established prognostic parameters, i.e., tumor subtype and Masaoka stage, although correlation with patient survival was not reached. Such findings suggest involvement of these RTKs in thymic neoplasia, as well as their potential utility as treatment targets.

Exosomes derived from immunogenically dying tumor cells as a versatile tool for vaccination against pancreatic cancer

Despite tremendous progress achieved in immunotherapy, many critical challenges in treating pancreatic ductal adenocarcinoma (PDAC) persist. Considering the poor vascularization of PDAC, after intramuscular administration exosomes can targeted deliver “cargos” to pancreatic tumors and bypass obstructions of the intrinsic overexpressed stroma through lymphatics. Herein, we propose a strategy to derive exosomes from immunogenically dying tumor cells and exploit their properties for several purposes, including antigen presentation, adjuvant supply, and “cargo” delivery of vaccines against pancreatic cancer via intramuscular injection. To enhance the immunostimulatory effects, the MART-1 peptide is modified to the exosomes to expand T-cell-related responses. Furthermore, CCL22 siRNA is electroporated into the exosomes (referred to as spMEXO) to hinder the CCR4/CCL22 axis between DCs and Tregs, thereby suppressing Treg expansion. Both in vitro and in vivo studies demonstrate that spMEXO can serve as an effective prophylactic vaccine to delay tumor growth, whereas combining spMEXO with PDAC first-line chemotherapeutics (co-administration of gemcitabine with albumin-paclitaxel) demonstrated significantly enhanced therapeutic effects in established PANC-02 tumors. Therefore, the present work provides an effective strategy to employ cancer vaccines through intramuscular injection in PDAC and highlights the potential of exosomes derived from immunogenically dying tumor cells as a versatile tool to develop nanovaccines for immunotherapy.

Intratumoral expression of IL-12 from lentiviral or RNA vectors acts synergistically with TLR4 agonist (GLA) to generate anti-tumor immunological memory.

Systemic interleukin-12 (IL12) anti-tumor therapy is highly potent but has had limited utility in the clinic due to severe toxicity. Here, we present two IL12-expressing vector platforms, both of which can overcome the deficiencies of previous systemic IL12 therapies: 1) an integrating lentiviral vector, and 2) a self-replicating messenger RNA formulated with polyethyleneimine. Intratumoral administration of either IL12 vector platform resulted in recruitment of immune cells, including effector T cells and dendritic cells, and the complete remission of established tumors in multiple murine models. Furthermore, concurrent intratumoral administration of the synthetic TLR4 agonist glucopyranosyl lipid A formulated in a stable emulsion (GLA-SE) induced systemic memory T cell responses that mediated complete protection against tumor rechallenge in all survivor mice (8/8 rechallenged mice), whereas only 2/6 total rechallenged mice treated with intratrumoral IL12 monotherapy rejected the rechallenge. Taken together, expression of vectorized IL12 in combination with a TLR4 agonist represents a varied approach to broaden the applicability of intratumoral immune therapies of solid tumors.

TGF-beta signaling in cancer radiotherapy

Transforming growth factor beta (TGF-β) plays key roles in regulating cellular proliferation and maintaining tissue homeostasis. TGF-β exerts tumor-suppressive effects in the early stages of carcinogenesis, but it also plays tumor-promoting roles in established tumors. Additionally, it plays a critical role in cancer radiotherapy. TGF-β expression or activation increases in irradiated tissues, and studies have shown that TGF-β plays dual roles in cancer radiosensitivity and is involved in ionizing radiation-induced fibrosis in different tumor microenvironments (TMEs). Furthermore, TGF-β promotes radioresistance by inducing the epithelial-mesenchymal transition (EMT), cancer stem cells (CSCs) and cancer-associated fibroblasts (CAFs), suppresses the immune system and facilitates cancer resistance. In particular, the links between TGF-β and the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) axis play a critical role in cancer therapeutic resistance. Growing evidence has shown that TGF-β acts as a radiation protection agent, leading to heightened interest in using TGF-β as a therapeutic target. The future of anti-TGF-β signaling therapy for numerous diseases appears bright, and the outlook for the use of TGF-β inhibitors in cancer radiotherapy as TME-targeting agents is promising.

Abstract P184: Anti-tumor efficacy of an MMAE conjugated antibody targeting cell surface TACE/ADAM17-cleaved Amphiregulin in breast cancer

Abstract The Epidermal Growth Factor Receptor ligand, Amphiregulin, is a key proliferative effector of estrogen receptor signaling in breast cancer and also plays a role in other malignancies. Amphiregulin is a single-pass transmembrane protein proteolytically processed by TACE/ADAM17 to release the soluble EGFR ligand, leaving a residual transmembrane stalk that is subsequently internalized. Here, we report the development of an antibody drug conjugate, GMF-1A3-MMAE, targeting an AREG neo-epitope revealed following ADAM17-mediated cleavage. The antibody does not interact with uncleaved Amphiregulin, providing a novel means of targeting cells with high rates of Amphiregulin shedding. Using fluorescent dye conjugation, we demonstrated that the antibody is internalized by cancer cells in a manner dependent on the presence of cell surface cleaved Amphiregulin. Antibodies conjugated with monomethyl auristatin E (MMAE) were cytotoxic in vitro and induced rapid regression of established breast tumor xenografts in immunocompromised mice. We further demonstrate that these antibodies recognize the Amphiregulin neo-epitope in formalin fixed paraffin embedded tumor tissue, suggesting their utility as a companion diagnostic for patient selection. Citation Format: Kristopher A. Lofgren, Sreeja Sreekumar, Edmund C. Jenkins, Kyle J. Ernzen, Paraic A. Kenny. Anti-tumor efficacy of an MMAE conjugated antibody targeting cell surface TACE/ADAM17-cleaved Amphiregulin in breast cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P184.

Abstract P200: Pre-clinical development of a dopamine receptor 2, PD-1 and CD47 trispecific antibody for treatment of small cell lung cancer

Abstract We developed a single domain VHH multi-specific antibody format. Multispecific antibodies have multiple mechanisms of action which may work independently or together, to achieve better clinical outcomes in cancers with high unmet medical need such as SCLC. Here we describe the preclinical development of a trispecific antibody (KB-436) that targets Dopamine Receptor 2 (DRD2), PD-1 and CD47. DRD2 is a G protein-coupled receptor upregulated in many cancer types where it correlates with decreased patient survival. In pre-clinical studies DRD2 is associated with cancer cell stemness and tumor growth. Clinical responses were achieved with small molecules targeting DRD2 and dopaminergic drugs. In SCLC, representing 15% of lung cancers, 60-70% of patients showed high expression of DRD2. Checkpoint inhibition has shown some efficacy in lung cancer where PD-L1 inhibitors were approved as first line therapy in SCLC . SCLC patients rapidly fail chemotherapy, develop resistance to treatment including to immunotherapy associated with lack of tumor infiltrating immune cells, appearance of metastases and large numbers of circulating tumor cells. These observations suggest a link between DRD2 expression and resistance to treatment, making this receptor an attractive target for a multispecific therapy. CD47 is overexpressed by many cancers and is also expressed on lymphocytes. Here, targeting CD47 is integral to T-cell engagement and redirection, in a mechanism distinct from CD3 mediated T-cell engagement. The VHH modules of KB-436 (anti-DRD2, anti-PD-1 and anti-CD47) mediate multiple mechanisms of action to achieve anti-tumor effect. The anti-DRD2 VHH induces intracellular signaling, the anti-PD-1 VHH restores T cell function, and the anti-CD47 VHH recruits T cells without their generalized activation and blocks interaction of CD47 with SIRPa. Treatment with anti-DRD2 antibody significantly suppressed tumor growth in the DRD2-positive NCI-H510A SCLC model in SCID mice. KB-436 anti-tumor efficacy was tested in several in vivo immuno-oncology xenograft models of human SCLC and other solid tumors , reconstituted with human PBMC or with CD34+ hemopoietic stem cells. Treatment suppressed tumor growth, enhanced the in vivo effect of cisplatin-treatment in a less chemosensitive NCI-H69 variant, blocked metastases formation in CD34+ humanized NCG mice bearing established NCI-H69 tumors, and blocked metastases formation and increased survival in tail vein metastatic models. Trispecific KB-436 has a half-life in mice of around 5 days similar to that of other antibodies. It is produced at high yield (6 g/L) in a manufacturing cell line, conventional purification yields 99% purity and notably displays high stability under accelerated stability testing. In conclusion, the trispecific KB-436 antibody, has strong in vivo anti-tumor activity mediated via multiple mechanisms of action, is easily expressed and purified and is very stable. Together, this data supports the clinical development of KB-436 in advanced metastatic solid cancer indications, including SCLC. Citation Format: Shugang Yao, Yun Cui, Anna Kazanats, Liying Gong, Claire Bonfils, Dominic Hou, Emily Chen, Elijus Undzys, Jacynthe Toulouse, Milica Krstic, Hiba Zahreddine, Israel Matos, Alex Zhou, Aniel Moya-Torres, Richard Wargachuk, Carl Gay, Lauren Byers, Gordon Ngan, Luis da Cruz, David Young. Pre-clinical development of a dopamine receptor 2, PD-1 and CD47 trispecific antibody for treatment of small cell lung cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P200.

Abstract P206: AB521 potently and selectively inhibits pro-tumorigenic gene transcription by Hypoxia-Inducible Factor (HIF)-2α in vitro and in vivo

Abstract Cells in the solid tumor microenvironment are frequently exposed to hypoxic conditions, necessitating molecular adaptations for survival. Of particular importance are transcriptional changes mediated by heterodimeric Hypoxia-Inducible Factor (HIF) proteins that consist of an oxygen-regulated α monomer (either HIF-1α, -2α, and -3α) coupled to a constitutively expressed β monomer (HIF-1β/ARNT). In normal oxygen conditions, HIF-2α is degraded following ubiquitination by the von Hippel-Lindau (pVHL) E3-ubiquitin ligase complex. Exposure to hypoxia, VHL mutation, or epigenetic silencing of pVHL leads to HIF-2α stabilization and transcription of pro-tumorigenic gene sets in both cancer and non-cancer cells. Inhibition of HIF-2α has been shown clinically to be an effective strategy to mitigate tumor growth, particularly in patients suffering from VHL disease or clear cell renal cell carcinoma (ccRCC), a cancer that has a particularly high prevalence of pVHL dysfunction. Applying a pharmacophore mapping and structure-based design approach, we identified a novel and potent small molecule HIF-2α inhibitor, AB521. AB521 avidly binds the HIF-2α PAS-B domain, preventing HIF-2α-mediated gene transcription. AB521 is characterized by a favorable preclinical pharmacokinetic profile and is projected to be suitable for once-daily dosing in humans. When delivered orally in mice, AB521 significantly regressed established 786-O xenograft tumors and decreased pharmacodynamic markers associated with HIF-2α in a dose-dependent manner. In vitro, AB521 potently inhibited HIF-2α-specific luciferase reporter transcription under high-serum conditions, VEGF protein secretion, colony formation in soft agar, and did not exhibit off-target cytotoxicity in 786-O cells. AB521 selectively inhibited HIF-2α-, but not HIF-1α-, mediated gene expression in hypoxic Hep3B hepatocellular carcinoma cells. AB521 also inhibited the transcriptional activity of endogenous HIF-2α in relevant human primary cell types, including endothelial cells and pro-tumorigenic M2-polarized macrophages. Importantly, inhibiting HIF-2α did not impact functionality of activated hypoxic human T cells, suggesting that AB521 would be favorable combination partner for I-O therapeutic agents. Indeed, expression of CD73, the primary enzyme responsible for synthesis of the immunosuppressive metabolite adenosine, was highly correlated with hypoxic signatures across several indications in publicly available bioinformatic datasets, suggesting combinations with adenosine pathway antagonists in ccRCC and beyond. In summary, AB521 is a novel and selective HIF-2α inhibitor with potent anti-tumor activity. Clinical evaluation of this molecule is expected to begin in the latter part of 2021. Citation Format: Kelsey E. Sivick Gauthier, Dana Piovesan, Soonweng Cho, Kenneth V. Lawson, Patrick G. Schweickert, Alejandra Lopez, Suan Liu, Timothy Park, Artur Mailyan, Jeremy T. A. Fournier, Joel W. Beatty, Samuel L. Drew, Jarek Kalisiak, Balint Gal, Guillaume Mata, Zhang Wang, Brandon R. Rosen, Clayton Hardman, Matthaw P. Epplin, Kai Yu, Karl T. Haelsig, Lixia Jin, Elaine Ginn, Jennie Au, Cesar A. Meleza, Joel Tencer, Amber Pham, Hyock J. Kwon, Stephen W. Young, Manmohan Leleti, Jay P. Powers, Matthew J. Walters. AB521 potently and selectively inhibits pro-tumorigenic gene transcription by Hypoxia-Inducible Factor (HIF)-2α in vitro and in vivo [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P206.

Vitamin D and Breast Cancer: Mechanistic Update.

ABSTRACTThe presence of the vitamin D receptor (VDR) in mammary gland and breast cancer has long been recognized, and multiple preclinical studies have demonstrated that its ligand, 1,25‐dihydroxyvitamin D (1,25D), modulates normal mammary gland development and inhibits growth of breast tumors in animal models. Vitamin D deficiency is common in breast cancer patients, and some evidence suggests that low vitamin D status enhances the risk for disease development or progression. Although many 1,25D‐responsive targets in normal mammary cells and in breast cancers have been identified, validation of specific targets that regulate cell cycle, apoptosis, autophagy, and differentiation, particularly in vivo, has been challenging. Model systems of carcinogenesis have provided evidence that both VDR expression and 1,25D actions change with transformation, but clinical data regarding vitamin D responsiveness of established tumors is limited and inconclusive. Because breast cancer is heterogeneous, the relevant VDR targets and potential sensitivity to vitamin D repletion or supplementation will likely differ between patient populations. Detailed analysis of VDR actions in specific molecular subtypes of the disease will be necessary to clarify the conflicting data. Genomic, proteomic, and metabolomic analyses of in vitro and in vivo model systems are also warranted to comprehensively understand the network of vitamin D–regulated pathways in the context of breast cancer heterogeneity. This review provides an update on recent studies spanning the spectrum of mechanistic (cell/molecular), preclinical (animal models), and translational work on the role of vitamin D in breast cancer. © 2021 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Adoptive transfer of tumor-specific Th9 cells eradicates heterogeneous antigen-expressing tumor cells.

In this issue of Cancer Cell, Xue etal. demonstrate that adoptive transfer of tumor-specific Th9 cells can eradicate established tumors containing antigen-loss-variant cells (ALVs) through both direct killing and bystander effects mediated by intratumoral accumulation of extracellular ATP (eATP) that promotes monocyte infiltration and stimulation of IFNα/β production.

Augmenting Adoptive T-cell Immunotherapy by Targeting the PD-1/PD-L1 Axis.

Cancer immunotherapy utilizing checkpoint blockade antibodies or adoptive cellular therapy (ACT) with tumor-specific T cells has led to unprecedented clinical responses in patients with cancer and has been considered one of the most significant breakthroughs in cancer treatment in the past decade. Nevertheless, many cancers remain refractory to these therapies due to the presence of an immunosuppressive tumor microenvironment. This has led to the innovative idea of combining ACT with checkpoint inhibition. A landmark 2004 study by Blank and colleagues published in Cancer Research was one of the original demonstrations that adoptive transfer of T cells lacking the negative T-cell regulator, PD-1, was able to restore functional T-cell antitumor activity, resulting in rapid regression of established tumors in a preclinical model. This work was instrumental in not only driving clinical studies utilizing checkpoint inhibition but also a new wave of recent trials involving checkpoint blockade in the setting of ACT.See related article by Blank and colleagues, Cancer Res 2004;64:1140-5.

Small-molecule inhibitors that disrupt the MTDH-SND1 complex suppress breast cancer progression and metastasis.

Metastatic breast cancer is leading health burden worldwide. Previous studies have shown that Metadherin (MTDH) promotes breast cancer initiation, metastasis and therapy resistance; however, the therapeutic potential of targeting MTDH remains largely unexplored. Here, we used genetically modified mice and demonstrate that genetic ablation of Mtdh inhibits breast cancer development through disrupting the interaction with Staphylococcal nuclease domain-containing 1 (SND1) which is required to sustain breast cancer progression in established tumors. We performed a small molecule compound screening to identify a class of specific inhibitors that disrupt the protein-protein interaction between MTDH-SND1, and show that our lead candidate compounds C26-A2 and C26-A6 suppressed tumor growth and metastasis, and enhanced chemotherapy sensitivity in preclinical models of triple-negative breast cancer. Our results demonstrate a significant therapeutic potential in targeting the MTDH-SND1 complex and identify a new class of therapeutic agents for metastatic breast cancer.

Targeting Innate Immunity in Breast Cancer Therapy: A Narrative Review.

Although breast cancer has been previously considered “cold” tumors, numerous studies are currently conducted to explore the great potentials of immunotherapies in improving breast cancer patient outcomes. In addition to the focus on stimulating adaptive immunity for antitumor responses, growing evidence showed the importance of triggering host innate immunity to eradicate established tumors and/or control tumor metastasis of breast cancer. In this review, we first briefly introduce the breast tumor immune microenvironment. We also discuss innate immune targets and pathways and mechanisms of their synergy with the adaptive antitumor response and other treatment strategies. Lastly, we review clinical trials targeting innate immune pathways for breast cancer therapies.

PRDM5 suppresses oesophageal squamous carcinoma cells and modulates 14-3-3zeta/Akt signalling pathway.

Dysregulation of PR (PRDI-BF1 and RIZ) domain protein 5 (PRDM5) expression has been shown to be associated with the progression of many malignancies. Nevertheless, the role and underlying mechanism of PRDM5 in oesophageal squamous cell carcinoma (ESCC) remain elusive. qRT-PCR was performed to analyze PRDM5 mRNA expression, and western blot was used to determine protein expression of PRDM5, MMP-2, MMP-9, 14-3-3zeta, pan-Akt and phosphorylated Akt expression. CCK-8 staining was employed to evaluate cell proliferation, while wound scratch assay and Transwell assay were carried out to detect cell migration. A tumour xenograft model of ESCC was also established to validate the effect of PRDM5. PRDM5 expression was downregulated in ESCC tissues and positively correlated with the overall survival of ESCC patients. Silencing PRDM5 expression promoted cell proliferation in ESCC cells, while overexpressing PRDM5 inhibited cell proliferation. Moreover, the migratory abilities of ESCC cells were promoted by PRDM5 knockdown but were attenuated by PRDM5 overexpression. Importantly, 14-3-3zeta expression, along with the phosphorylation of Akt, was suppressed by PRDM5 in ESCC cells. In the established tumour xenograft model, PRDM5 regulated ESCC tumour growth as well as the expression of 14-3-3zeta and phosphorylation of Akt protein. In conclusion, PRDM5suppresses ESCC cell proliferation and migration and negatively regulates 14-3-3zeta/Akt signalling pathway in vitro and in vivo.

Combination of Carriers with Complementary Intratumoral Microdistributions of Delivered α-Particles May Realize the Promise for 225Ac in Large, Solid Tumors.

α-particle radiotherapy has already been shown to be impervious to most resistance mechanisms. However, in established (i.e., large, vascularized) soft-tissue lesions, the diffusion-limited penetration depths of radiolabeled antibodies or nanocarriers (≤50-80 μm) combined with the short range of α-particles (4-5 cell diameters) may result in only partial tumor irradiation, potentially limiting treatment efficacy. To address this challenge, we combined carriers with complementary intratumoral microdistributions of the delivered α-particles. We used the α-particle generator 225Ac, and we combined a tumor-responsive liposome (which, on tumor uptake, releases into the interstitium a highly diffusing form of its radioactive payload [225Ac-DOTA], potentially penetrating the deeper parts of tumors where antibodies do not reach) with a separately administered, less-penetrating radiolabeled antibody (irradiating the tumor perivascular regions where liposome contents clear too quickly). Methods: In a murine model with orthotopic human epidermal growth factor receptor 2-positive BT474 breast cancer xenografts, the biodistributions of each carrier were evaluated, and the control of tumor growth was monitored after administration of the same total radioactivity of 225Ac delivered by the 225Ac-DOTA-encapsulating liposomes, by the 225Ac-DOTA-SCN--labeled trastuzumab, and by both carriers at equally split radioactivities. Results: Tumor growth was significantly more inhibited when the same total injected radioactivity was divided between the 2 separate carriers than when delivered by either of the carriers alone. The combined carriers enabled more uniform intratumoral microdistributions of α-particles, at a tumor dose that was lower than the dose delivered by the antibody alone. Conclusion: This strategy demonstrates that more uniform microdistributions of the delivered α-particles within established solid tumors improve efficacy even at lower tumor doses. Augmentation of antibody-targeted α-particle therapies with tumor-responsive liposomes may address partial tumor irradiation, improving therapeutic effects.

Two diverse carriers are better than one: A case study in α-particle therapy for prostate specific membrane antigen-expressing prostate cancers.

Partial and/or heterogeneous irradiation of established (i.e., large, vascularized) tumors by α‐particles that exhibit only a 4–5 cell‐diameter range in tissue, limits the therapeutic effect, since regions not being hit by the high energy α‐particles are likely not to be killed. This study aims to mechanistically understand a delivery strategy to uniformly distribute α‐particles within established solid tumors by simultaneously delivering the same α‐particle emitter by two diverse carriers, each killing a different region of the tumor: (1) the cancer‐agnostic, but also tumor‐responsive, liposomes engineered to best irradiate tumor regions far from the vasculature, and (2) a separately administered, antibody, targeting any cancer‐cell's surface marker, to best irradiate the tumor perivascular regions. We demonstrate that on a prostate specific membrane antigen (PSMA)‐expressing prostate cancer xenograft mouse model, for the same total injected radioactivity of the α‐particle emitter Actinium‐225, any radioactivity split ratio between the two carriers resulted in better tumor growth inhibition compared to the tumor inhibition when the total radioactivity was delivered by any of the two carriers alone. This finding was due to more uniform tumor irradiation for the same total injected radioactivity. The killing efficacy was improved even though the tumor‐absorbed dose delivered by the combined carriers was lower than the tumor‐absorbed dose delivered by the antibody alone. Studies on spheroids with different receptor‐expression, used as surrogates of the tumors' avascular regions, demonstrated that our delivery strategy is valid even for as low as 1+ (ImmunoHistoChemistry score) PSMA‐levels. The findings presented herein may hold clinical promise for those established tumors not being effectively eradicated by current α‐particle radiotherapies.