Ex vivo drug testing of patient-derived lung organoids to predict treatment responses for personalized medicine

Lung cancer is the leading cause of global cancer-related mortality resulting in ∼ 1.8 million deaths annually. Systemic, molecular targeted, and immune therapies have provided significant improvements of survival outcomes for patients. However, drug resistance usually arises and there is an urgent need for novel therapy screening and personalized medicine. 3D patient-derived organoid (PDO) models have emerged as a more effective and efficient alternative for ex vivo drug screening than 2D cell culture and patient-derived xenograft (PDX) models. In this review, we performed an extensive search of lung cancer PDO-based ex vivo drug screening studies. Lung cancer PDOs were successfully established from fresh or bio-banked sections and/or biopsies, pleural effusions and PDX mouse models. PDOs were subject to ex vivo drug screening with chemotherapy, targeted therapy and/or immunotherapy. PDOs consistently recapitulated the genomic alterations and drug sensitivity of primary tumors. Although sample sizes of the previous studies were limited and some technical challenges remain, PDOs showed great promise in the screening of novel therapy drugs. With the technical advances of high throughput, tumor-on-chip, and combined microenvironment, the drug screening process using PDOs will enhance precision care of lung cancer patients.

Phagocytosis-initiated tumor hybrid cells acquire a c-Myc-mediated quasi-polarization state for immunoevasion and distant dissemination

While macrophage phagocytosis is an immune defense mechanism against invading cellular organisms, cancer cells expressing the CD47 ligand send forward signals to repel this engulfment. Here we report that the reverse signaling using CD47 as a receptor additionally enhances a pro-survival function of prostate cancer cells under phagocytic attack. Although low CD47-expressing cancer cells still allow phagocytosis, the reverse signaling delays the process, leading to incomplete digestion of the entrapped cells and subsequent tumor hybrid cell (THC) formation. Viable THCs acquire c-Myc from parental cancer cells to upregulate both M1- and M2-like macrophage polarization genes. Consequently, THCs imitating dual macrophage features can confound immunosurveillance, gaining survival advantage in the host. Furthermore, these cells intrinsically express low levels of androgen receptor and its targets, resembling an adenocarcinoma-immune subtype of metastatic castration-resistant prostate cancer. Therefore, phagocytosis-generated THCs may represent a potential target for treating the disease.

AXL-initiated paracrine activation of pSTAT3 enhances mesenchymal and vasculogenic supportive features of tumor-associated macrophages

Tumor-associated macrophages (TAMs) are integral to the development of complex tumor microenvironments (TMEs) and can execute disparate cellular programs in response to extracellular cues. However, upstream signaling processes underpinning this phenotypic plasticity remain to be elucidated. Here, we report that concordant AXL-STAT3 signaling in TAMs is triggered by lung cancer cells or cancer-associated fibroblasts in the cytokine milieu. This paracrine action drives TAM differentiation toward a tumor-promoting "M2-like" phenotype with upregulation of CD163 and putative mesenchymal markers, contributing to TAM heterogeneity and diverse cellular functions. One of the upregulated markers, CD44, mediated by AXL-IL-11-pSTAT3 signaling cascade, enhances macrophage ability to interact with endothelial cells and facilitate formation of primitive vascular networks. We also found that AXL-STAT3 inhibition can impede the recruitment of TAMs in a xenograft mouse model, thereby suppressing tumor growth. These findings suggest the potential application of AXL-STAT3-related markers to quantitatively assess metastatic potential and inform therapeutic strategies in lung cancer.

Abstract LBA025: AXL-STAT3 targeting of lung tumor microenvironments

The tumor microenvironment contains multiple cell types, each providing a unique functionality in support of malignant growth. To prepare a pro-metastatic niche, a tight signaling network may be present to coordinate delivery of co-stimulatory signals among different cell subpopulations. Here, we report that AXL signaling collaborates with STAT3 to create a symbiotic ecosystem that favors partial epithelial-mesenchymal transition of cancer cells, pro-tumorigenic remodeling of fibroblasts, and M2 polarization of macrophages. To facilitate intercellular communication, AXL-regulated IL-11 secreted from cancer cells and fibroblasts binds to surface GP130 on macrophages to activate STAT3 signaling for M2 polarization. Disruption of AXL-STAT3 circuit not only compromises this signaling co-dependency in lung cancer cells implanted in xenograft mice, but also limits their ability to conscript murine fibroblasts, macrophages, and other immune cells to form a shared habitat for tumor growth and invasion. Therefore, targeting AXL-STAT3 network is an attractive strategy to render inoperative tumor microenvironments that exploit this cellular synchronicity for tumor progression. Significance: Combined targeting of AXL and STAT3 signaling that facilitates co-dependency between malignant and non-malignant cells in tumor microenvironments is a promising strategy for the treatment of advanced lung adenocarcinomas.

Citation Format: Josephine A. Taverna. AXL-STAT3 targeting of lung tumor microenvironments [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 LBA025.

Contacts with Macrophages Promote an Aggressive Nanomechanical Phenotype of Circulating Tumor Cells in Prostate Cancer

Aggressive tumors of epithelial origin shed cells that intravasate and become circulating tumor cells (CTC). The CTCs that are able to survive the stresses encountered in the bloodstream can then seed metastases. We demonstrated previously that CTCs isolated from the blood of prostate cancer patients display specific nanomechanical phenotypes characteristic of cell endurance and invasiveness and patient sensitivity to androgen deprivation therapy. Here we report that patient-isolated CTCs are nanomechanically distinct from cells randomly shed from the tumor, with high adhesion as the most distinguishing biophysical marker. CTCs uniquely coisolated with macrophage-like cells bearing the markers of tumor-associated macrophages (TAM). The presence of these immune cells was indicative of a survival-promoting phenotype of "mechanical fitness" in CTCs based on high softness and high adhesion as determined by atomic force microscopy. Correlations between enumeration of macrophages and mechanical fitness of CTCs were strong in patients before the start of hormonal therapy. Single-cell proteomic analysis and nanomechanical phenotyping of tumor cell-macrophage cocultures revealed that macrophages promoted epithelial-mesenchymal plasticity in prostate cancer cells, manifesting in their mechanical fitness. The resulting softness and adhesiveness of the mechanically fit CTCs confer resistance to shear stress and enable protective cell clustering. These findings suggest that selected tumor cells are coached by TAMs and accompanied by them to acquire intermediate epithelial/mesenchymal status, thereby facilitating survival during the critical early stage leading to metastasis. SIGNIFICANCE: The interaction between macrophages and circulating tumor cells increases the capacity of tumor cells to initiate metastasis and may constitute a new set of blood-based targets for pharmacologic intervention.

Toward uncharted territory of cellular heterogeneity: advances and applications of single-cell RNA-seq

Among single-cell analysis technologies, single-cell RNA-seq (scRNA-seq) has been one of the front runners in technical inventions. Since its induction, scRNA-seq has been well received and undergone many fast-paced technical improvements in cDNA synthesis and amplification, processing and alignment of next generation sequencing reads, differentially expressed gene calling, cell clustering, subpopulation identification, and developmental trajectory prediction. scRNA-seq has been exponentially applied to study global transcriptional profiles in all cell types in humans and animal models, healthy or with diseases, including cancer. Accumulative novel subtypes and rare subpopulations have been discovered as potential underlying mechanisms of stochasticity, differentiation, proliferation, tumorigenesis, and aging. scRNA-seq has gradually revealed the uncharted territory of cellular heterogeneity in transcriptomes and developed novel therapeutic approaches for biomedical applications. This review of the advancement of scRNA-seq methods provides an exploratory guide of the quickly evolving technical landscape and insights of focused features and strengths in each prominent area of progress.

Abstract B29: AXL Inhibitor TP-0903 attenuates TGFβ-Hippo signaling in lung adenocarcinoma cells

Background: Non-small cell lung cancer (NSCLC) is a molecularly heterogeneous disease with a high propensity for drug resistance and metastasis. AXL, a member of the Tyro3-AXL-Mer (TAM) family of receptor tyrosine kinases, is a central regulator of epithelial-to-mesenchymal transition (EMT) and enables tumor cells to invade and acquire drug resistance. AXL is overexpressed in NSCLC and its expression correlates positively with tumor invasion, drug resistance, and negatively predicts overall survival. We mechanistically interrogated the effects of the AXL inhibitor, TP-0903, on EMT in NSCLC cells using transcriptomic and proteomic profiling.

Methods: Atomic force microscopy, Western blot analysis, RNA sequencing, and mass cytometry (CyTOF) were used to evaluate the phenotypic, transcriptomic, and proteomic profiles of A549 cells treated with 40 nM TP-0903 or shAXL knockdown. A549 and H1650 NSCLC xenograft models were used to explore the consequences of AXL inhibition in vivo.

Results: As expected, TP-0903 treatment attenuated AXL signaling and downstream phosphorylation in the A549 cells. Interestingly, the treatment also reduced gene expression responses to TGFβ-Hippo signaling by disrupting the transcriptional complexes formed by SMAD2/3, SMAD4, YAP1, and TAZ. Consistent with AXL inhibition, TP-0903 reversed the mesenchymal phenotype in A549 and H2009 cell lines and decreased their migratory potential in culture. The CyTOF analysis on TP-0903-treated cells identified resistant clones overexpressing TGFβ receptor II (TGFBR2) and TAZ proteins and displaying hybrid EMT phenotypes. TP-0903 was also active in suppressing A549 or H1650 tumor growth in vivo.

Conclusions: We are the first to report the interplay between AXL and TGFβ-Hippo signaling axis. TP-0903 has excellent therapeutic promise in NSCLC and we speculate that TP-0903 can target mesenchymal transitional states in NSCLC, possibly through the inhibition of the AXL-TGFβ-Hippo signaling axis.

Citation Format: Josephine A. Taverna, Chia-Nung Hung, Chun-Lin Lin, Pawel A. Osmulski, Maria E. Gaczynska, Chiou-Miin Wang, Nicholas D. Lucio, Meizhen Chen, Chih-Wei Chou, Alia Nazarullah, Shellye R. Lampkin, Lianquin Qiu, David J. Bearss, Steve Warner, Lars Mouritsen, Mark Wade, Daniel DeArmond, Ruben Mesa, Nameer Kirma, Tim H.-M. Huang. AXL Inhibitor TP-0903 attenuates TGFβ-Hippo signaling in lung adenocarcinoma cells [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr B29.

Single-Cell Proteomic Profiling Identifies Combined AXL and JAK1 Inhibition as a Novel Therapeutic Strategy for Lung Cancer

Cytometry by time-of-flight (CyTOF) simultaneously measures multiple cellular proteins at the single-cell level and is used to assess intertumor and intratumor heterogeneity. This approach may be used to investigate the variability of individual tumor responses to treatments. Herein, we stratified lung tumor subpopulations based on AXL signaling as a potential targeting strategy. Integrative transcriptome analyses were used to investigate how TP-0903, an AXL kinase inhibitor, influences redundant oncogenic pathways in metastatic lung cancer cells. CyTOF profiling revealed that AXL inhibition suppressed SMAD4/TGFβ signaling and induced JAK1-STAT3 signaling to compensate for the loss of AXL. Interestingly, high JAK1-STAT3 was associated with increased levels of AXL in treatment-naïve tumors. Tumors with high AXL, TGFβ, and JAK1 signaling concomitantly displayed CD133-mediated cancer stemness and hybrid epithelial-to-mesenchymal transition features in advanced-stage patients, suggesting greater potential for distant dissemination. Diffusion pseudotime analysis revealed cell-fate trajectories among four different categories that were linked to clinicopathologic features for each patient. Patient-derived organoids (PDO) obtained from tumors with high AXL and JAK1 were sensitive to TP-0903 and ruxolitinib (JAK inhibitor) treatments, supporting the CyTOF findings. This study shows that single-cell proteomic profiling of treatment-naïve lung tumors, coupled with ex vivo testing of PDOs, identifies continuous AXL, TGFβ, and JAK1-STAT3 signal activation in select tumors that may be targeted by combined AXL-JAK1 inhibition. SIGNIFICANCE: Single-cell proteomic profiling of clinical samples may facilitate the optimal selection of novel drug targets, interpretation of early-phase clinical trial data, and development of predictive biomarkers valuable for patient stratification.

Spatial EGFR Dynamics and Metastatic Phenotypes Modulated by Upregulated EphB2 and Src Pathways in Advanced Prostate Cancer

Advanced prostate cancer is a very heterogeneous disease reflecting in diverse regulations of oncogenic signaling pathways. Aberrant spatial dynamics of epidermal growth factor receptor (EGFR) promote their dimerization and clustering, leading to constitutive activation in oncogenesis. The EphB2 and Src signaling pathways are associated with the reorganization of the cytoskeleton leading to malignancy, but their roles in regulating EGFR dynamics and activation are scarcely reported. Using single-particle tracking techniques, we found that highly phosphorylated EGFR in the advanced prostate cancer cell line, PC3, was associated with higher EGFR diffusivity, as compared with LNCaP and less aggressive DU145. The increased EGFR activation and biophysical dynamics were consistent with high proliferation, migration, and invasion. After performing single-cell RNA-seq on prostate cancer cell lines and circulating tumor cells from patients, we identified that upregulated gene expression in the EphB2 and Src pathways are associated with advanced malignancy. After dasatinib treatment or siRNA knockdowns of EphB2 or Src, the PC3 cells exhibited significantly lower EGFR dynamics, cell motility, and invasion. Partial inhibitory effects were also found in DU145 cells. The upregulation of parts of the EphB2 and Src pathways also predicts poor prognosis in the prostate cancer patient cohort of The Cancer Genome Atlas. Our results provide evidence that overexpression of the EphB2 and Src signaling pathways regulate EGFR dynamics and cellular aggressiveness in some advanced prostate cancer cells.

Polycythaemia: an unusual presentation of multiple myeloma

In contrast to anaemia, polycythaemia is a distinctly uncommon finding in patients with multiple myeloma. We describe the presence of otherwise unexplained polycythaemia in a 57-year-old Caucasian man who was found to have IgG κ multiple myeloma. After treatment of myeloma, the polycythaemia resolved. We reviewed previous reports of polycythaemia associated with multiple myeloma and discuss potential pathophysiological mechanisms that link these 2 conditions.

Role of Maintenance Therapy after High-Dose Chemotherapy and Autologous Hematopoietic Cell Transplantation in Aggressive Lymphomas: A Systematic Review

Significant uncertainty exists in regard to the efficacy of maintenance therapy after high-dose chemotherapy (HDC) as well as autologous stem cell transplantation (ASCT) for the treatment of patients with aggressive lymphoma. A systematic review was performed to evaluate the effectiveness of post-ASCT maintenance therapy in patients with relapsed/refractory lymphoma. A comprehensive literature search yielded 4476 studies and a total of 42 studies (11 randomized controlled trials [RCT], 9 retrospective comparative studies, and 22 single-arm studies) were included in the systematic review. There was significant heterogeneity in study design, chemotherapeutic regimens, post-ASCT maintenance strategies, patient enrollment criteria, and study endpoints. Our findings suggest that post-ASCT maintenance immune-targeting strategies, including PD-1/PD-L1 blocking antibodies, rituximab, and brentuximab, may improve progression-free survival but not overall survival. Collectively, the results indicate a need for testing new strategies with well-designed and adequately powered RCTs to better address the role of post-ASCT maintenance in relapsed/refractory lymphomas.

Double-Blind, Randomized Trial of Alternative Letrozole Dosing Regimens in Postmenopausal Women with Increased Breast Cancer Risk

Aromatase inhibitors (AI) profoundly suppress estrogen levels in postmenopausal women and are effective in breast cancer prevention among high-risk postmenopausal women. Unfortunately, AI treatment is associated with undesirable side effects that limit patient acceptance for primary prevention of breast cancer. A double-blind, randomized trial was conducted to determine whether low and intermittent doses of letrozole can achieve effective estrogen suppression with a more favorable side-effect profile. Overall, 112 postmenopausal women at increased risk for breast cancer were randomized to receive letrozole at 2.5 mg once daily (QD, standard dose arm), 2.5 mg every Monday, Wednesday, and Friday (Q-MWF), 1.0 mg Q-MWF, or 0.25 mg Q-MWF for 24 weeks. Primary endpoint was suppression in serum estradiol levels at the end of letrozole intervention. Secondary endpoints included changes in serum estrone, testosterone, C-telopeptide (marker of bone resorption), lipid profile, and quality-of-life measures (QoL) following treatment. Significant estrogen suppression was observed in all dose arms with an average of 75% to 78% and 86% to 93% reduction in serum estradiol and estrone levels, respectively. There were no differences among dose arms with respect to changes in C-telopeptide levels, lipid profile, adverse events (AE), or QoL measures. We conclude that low and intermittent doses of letrozole are not inferior to standard dose in estrogen suppression and resulted in a similar side-effect profile compared with standard dose. Further studies are needed to determine the feasibility of selecting an effective AI dosing schedule with better tolerability.

Successful adjuvant treatment of recalcitrant mucous membrane pemphigoid with anti-CD20 antibody rituximab

Rituximab is a humanized monoclonal antibody directed against CD20-positive B cells and originally developed for the treatment of non-Hodgkins lymphoma. We report a case of severe mucous membrane pemphigoid responsive to rituximab infusions. The clinical presentation, etiology, and management options for mucous membrane pemphigoid are also discussed.

Case reports: nodular vasculitis responsive to mycophenolate mofetil

Mycophenolate mofetil is commonly used as a steroid-sparing agent effective in the management of erythema nodosum, idiopathic nodular panniculitis (Pfiefer-Weber-Christian disease), bullous pemphigoid, pemphigus vulgaris, and psoriasis. We report a case of nodular vasculitis responsive to mycophenolate mofetil. The clinical presentation, etiology, and management options for nodular vasculitis are discussed.