IL1R1+ cancer-associated fibroblasts drive tumor development and immunosuppression in colorectal cancer

Fibroblasts have a considerable functional and molecular heterogeneity and can play various roles in the tumor microenvironment. Here we identify a pro-tumorigenic IL1R1⁺, IL-1-high-signaling subtype of fibroblasts, using multiple colorectal cancer (CRC) patient single cell sequencing datasets. This subtype of fibroblasts is linked to T cell and macrophage suppression and leads to increased cancer cell growth in 3D co-culture assays. Furthermore, both a fibroblast-specific IL1R1 knockout and IL-1 receptor antagonist Anakinra administration reduce tumor growth in vivo. This is accompanied by reduced intratumoral Th17 cell infiltration. Accordingly, CRC patients who present with IL1R1-expressing cancer-associated-fibroblasts (CAFs), also display elevated levels of immune exhaustion markers, as well as an increased Th17 score and an overall worse survival. Altogether, this study underlines the therapeutic value of targeting IL1R1-expressing CAFs in the context of CRC.

OS05.5.A Glioblastoma-instructed microglia transit to heterogeneous phenotypic states with dendritic cell-like features in patient tumors and patient-derived orthotopic xenografts

Background

A major contributing factor to Glioblastoma (GBM) development and progression is its ability to evade the immune system by creating an immune-suppressive tumor microenvironment (TME). GBM-associated myeloid cells, including resident microglia, macrophages and other peripheral immune cells are generally geared towards tumor-supportive roles. It is however unclear whether such recruited myeloid cells are phenotypically and functionally identical. Here, we aim to understand the heterogeneity of the GBM TME, using an unbiased, marker-free approach to systematically characterize cell type identities at the molecular and functional levels.

Material and Methods

We applied single-cell RNA-sequencing, multicolor flow cytometry, immunohistochemical analyses and functional studies to examine the heterogeneous TME instructed by GBM cells. GBM patient-derived orthotopic xenografts (PDOXs) representing different tumor phenotypes were compared to glioma mouse GL261 model and patient tumors.

Results

We show that PDOX models recapitulate major components of the TME found in human GBM. Human GBM cells reciprocally interact with mouse cells to create a GBM-specific TME. The most prominent transcriptomic adaptations are found in tumor-associated macrophages (TAMs), which are largely of microglial origin. We reveal inter-patient heterogeneity of TAMs and identify key signatures of distinct phenotypic states within the microglia-derived TAMs across distinct GBM landscapes. GBM-educated microglia adapt expression of genes involved in immunosuppression, migration, phagocytosis and antigen presentation, indicating functional cross-talk with GBM cells. We identify novel phenotypic states with astrocytic and endothelial-like features. Identified gene signatures and phenotypic states are confirmed in GBM patient tumor tissue. Finally we show that temozolomide treatment leads to transcriptomic adaptation of not only the GBM tumor cells but also adjacent TME components.

Conclusion

Our data provide insights into the phenotypic adaptation of the heterogeneous TME instructed by GBM tumor. We confirm a crucial role of microglia in supporting the immunosuppressive TME and show that PDOXs allow to monitor the highly plastic GBM ecosystem and its phenotypic adaptations upon treatment. This work further confirms the clinical relevance of PDOX avatars for testing novel therapeutics including modalities designed to target the myeloid compartment.

PL02.3. A Phenotypic heterogeneity and plasticity as resistance mechanisms in Glioblastoma

BACKGROUND

Glioblastomas are among the most heterogeneous tumors, which hampers patient stratification and development of effective therapies. Glioblastomas create a dynamic ecosystem, where heterogeneous tumor cells interact with the tumor microenvironment to establish different niches. Upon tumor growth, Glioblastoma cells manifest remarkable plasticity and respond flexibly to selective pressures by transiting towards states favorable to the new tumor microenvitonment. How this phenotypic plasticity contributes to treatment resistance is currently less clear. The exact nature of treatment resistant, tolerant and sensitive Glioblastoma cells remains unresolved. Further studies at the single cell level are needed to reveal transient and long-term signatures of the resistant states.

MATERIAL AND METHODS

To investigate long-term phenotypic changes upon treatment at the single cell level we performed single cell RNA-seq (scRNA-seq) on the longitudinal patient-derived xenograft (PDOX) models derived from Glioblastoma patient tumors prior and after the standard-of-care treatment. In addition, direct treatment of PDOXs with temozolomide combined with scRNA-seq allowed revealing short-term transcriptomic changes both in tumor cells and in the mouse-derived cells forming tumor microenvironment. Advanced computational algorithms, including reference-free deconvolution methods, were applied to reveal treatment resistance signatures and master regulators of the identified treatment-resistant subpopulations.

RESULTS

We show that PDOX models recapitulate all the major cell types and transcriptional programs reported in Glioblastoma patient samples, providing clinically relevant models for investigating treatment resistance signatures of tumor cells and associated tumor microenvironment. Analysis of treatment naïve and treated Glioblastomas at the single cell level revealed presence of pre-existing treatment resistant states as well as newly established resistant subpopulatons. Certain transcriptomic changes are preserved long term, regardless of the lack of genetic evolution of the tumor cells.

CONCLUSION

Phenotypic plasticity is an important factor contributing to resistance mechanisms in Glioblastoma. Key molecular regulators of tumor cell plasticity towards treatment resistance states represent novel targets for future combinatory treatments.

PL3.4 Intrinsic tumor plasticity in Glioblastoma allows for recreation of stem like-states and efficient tumor cell adaptation to new microenvironments

BACKGROUND

Cellular heterogeneity has been well established within numerous cancer types, including malignant brain tumours. Initially, cancer stem cells (CSC) have been accounted for formation of phenotypic heterogeneity and tumor progression in glioblastoma (GBM). Recent data, however, suggest that CSCs may not represent a stable entity and intrinsic plasticity plays a key role in tumor adaptation to changing microenvironments. The question arises whether CSCs are a defined subpopulation of tumor cells or whether they represent a changing entity that any cancer cell can adopt depending on the environmental conditions.

MATERIAL AND METHODS

Intra-tumoral phenotypic heterogeneity was interrogated at the single cell transcriptomic and proteomic level in GBM patient-derived orthotopic xenografts (PDOXs) and stem-like cultures. Tumor cell subpopulations were further classified based on expression of four stem cell-associated membrane markers (CD133, CD15, A2B5 and CD44). The resulting 16 subpopulations were FACS isolated and functionally analyzed. Mathematical Markov modelling was applied to calculate state transitions between cell states.

RESULTS

GBM patient biopsies, PDOXs and stem-like cell cultures display remarkable stem cell-associated intra-tumoral heterogeneity. Independent of marker expression, all analysed tumor subpopulations carried stem-cell properties and had the capacity to recreate phenotypic heterogeneity. Mathematical modeling revealed a different propensity in reforming the original heterogeneity over time, which was independent of the proliferation index but linked to tumorigenic potential. Although subpopulations varied in their potential to adapt to new environments, all were able to reach a steady state microenvironment-specific equilibrium.

CONCLUSION

Our results suggest that phenotypic heterogeneity in GBM results from intrinsic plasticity allowing tumor cells to effectively adapt to new microenvironments. Cellular states are non-hierarchical, reversible and occur via stochastic state transitions of existing populations, striving towards an equilibrium instructed by the microenvironment. Our data provides evidence that CSCs do not represent a clonal entity defined by distinct functional properties and transcriptomic signatures, but rather a cellular state that is determined by environmental conditions, which has implications for the design of treatment strategies targeting CSC-like states.

Local production of interleukin-4 during radiation-induced pneumonitis and pulmonary fibrosis in rats: macrophages as a prominent source of interleukin-4

Fibrosis of lung tissue is a frequent and serious consequence of radiotherapy of mammary carcinoma. The pathogenesis of radiation-induced pulmonary fibrosis remains unclear. Cytokines such as transforming growth factor beta (TGFbeta) and interleukin-4 (IL-4) have been reported to stimulate collagen synthesis in fibroblasts in vitro. The aim of this study was to document the presence of IL-4 during the development of post-irradiation lung fibrosis. Right lungs of male Fischer rats were irradiated with a single dose of 20 Gy and IL-4 expression in the irradiated lungs was monitored for a period of three months. IL-4 gene transcription as determined by ribonuclease protection assay (RPA) as well as IL-4 synthesis as shown by Western blotting increased in the irradiated lungs reaching a plateau concentration within 3 weeks after irradiation. Enhanced IL-4 production was still detected at day 84 after irradiation. The cellular origin of IL-4 was analyzed by in situ hybridization and two-color immunofluorescence on lung tissue sections and on cytospin preparations of leukocytes obtained from bronchoalveolar lavages. These experiments revealed a substantial IL-4 production by macrophages during development of post-irradiation lung fibrosis.

Respiratory failure produced by severe procainamide intoxication in a patient with preexisting peripheral neuropathy caused by amiodarone

We describe a patient in whom respiratory failure, due to extreme neuromuscular weakness, was produced by procainamide intoxication superimposed on a peripheral neuropathy secondary to long-term amiodarone therapy. Respiratory failure reversed rapidly after procainamide was discontinued, and the serum level fell to a therapeutic range.

Complications of transthoracic needle biopsy decreased with isobutyl 2-cyanoacrylate: a pilot study

To explore the possibility of performing percutaneous lung biopsy safely in patients mechanically ventilated with positive-end expiratory pressure (PEEP), transthoracic needle biopsy was performed in 16 anesthetized mongrel dogs mechanically ventilated with 10 cm H2O of PEEP. To obtain the biopsy sample, a 25-gauge "skinny needle" was passed through a 20-gauge sheath and placed up to 6.25 cm deep. After satisfactory samples were obtained, both needles were withdrawn in the control group, but in the treated group, the outer sheath was used to inject 0.5 ml of isobutyl 2-cyanoacrylate to seal the needle track. Pneumothorax was present in 7 (87.5%) of 8 dogs in the control group and in 2 (25%) of 8 dogs in the treated group (p = .0147). Lung tissue exhibited an apparent foreign-body granulomatous inflammatory reaction. This technique could extend the benefits of transthoracic needle biopsy to mechanically ventilated patients, but further studies to prove the safety of isobutyl 2-cyanoacrylate are necessary.