P10.05.B Platelet-derived growth factor signalling pathways in patient-derived glioblastoma cells

Background

Platelet-derived growth factor (PDGF) signalling is essential in the development and maintenance of the neurovasculature. Of particular importance is PDGFRβ signalling for the recruitment and maintenance of the mural cell type pericytes, which occupy an important position in coordinating blood-brain barrier functions. The PDGF pathway is also implicated in glioblastoma, where overexpression of PDGFRα is a signature of the proneural subtype of the highly malignant and invasive tumour. The expression and signalling of both PDGFRα and β by tumour cells have been implicated in tumorigenesis and progression. Therefore, we sought to study PDGF receptor signalling in primary human-derived glioblastoma tumour cells to gain a better understanding of the signalling mechanisms driven by these receptors.

Material and Methods

Primary human epilepsy pericytes and glioblastoma tumour cells were isolated from surgical resections obtained from consenting patients at Auckland City Hospital. PDGF signalling pathways were investigated through treatment with exogenous PDGF ligands. Pathway activation was quantified using immunocytochemistry, human cytokine XL Proteome Profiler and cytometric bead arrays.

Results

PDGF-BB and PDGF-DD treatment led to the activation of PDGFRβ in pericyte cultures, which mediated the activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/Akt cascades, ultimately increasing pericyte proliferation and cytokine secretion. PDGF-AA treatment resulted in transient MAPK activation, but was not followed by increased proliferation in pericytes. In contrast, although PDGF-AA, -BB and -DD induced PDGFRα internalisation (and PDGF-BB and -DD induced PDGFRβ internalisation) in GBM tumour cells, this did not result in MAPK or PI3K/Akt activation or cell proliferation.

Conclusion

Despite PDGF receptor expression, the GBM tumour cells, in contrast to pericytes, surprisingly displayed a lack of responses to ligand stimulation through either PDGFRα or PDGFRβ. This warrants further investigation into the signalling mechanisms behind tumour cells to better understand tumour biology.

P12.07.B Getting to the core of microglia versus bone marrow-derived macrophages in glioblastoma

Background

Microglia and bone marrow-derived macrophages (BMDMs) are two ontogenetically distinct myeloid populations present within glioblastoma that can comprise 30-50% of the tumour mass. Historically, these cell types have been conflated and studied as a single population of ‘tumour-associated macrophages’. Recent advances in single-cell omics have allowed population delineation, suggesting microglia and BMDMs may play different roles within the tumour and subsequently differentially affect tumour progression. Despite building evidence for the unique functions of these cells within glioblastoma, the inherent heterogeneity of the tumour landscape has complicated such studies. Indeed, macrophages exist as phenotypically and functionally diverse populations that are polarised in a context-dependent manner. Hence, to understand the differences between microglia and BMDMs within glioblastoma, both ontogeny and spatial location must be considered.

Material and Methods

To elucidate the functional roles of microglia and BMDMs across the tumour landscape, a publicly available RNAseq dataset was utilised to classify myeloid cells into four populations based on spatial location and ontogeny. These were tumour core BMDMs and microglia, or tumour periphery BMDMs and microglia. Differential gene analysis was then performed to identify significant differentially expressed genes (DEGs) between classified myeloid populations. Tumour core DEGs were then compared against the Ivy Glioblastoma Atlas to define their expression across anatomical tumour regions. Finally, myeloid DEGs were validated at the protein level on human glioblastoma tissue through immunohistochemistry.

Results

Microglia and BMDMs showed different spatial distributions across the tumour landscape and displayed distinct functional expression profiles. Microglia held a more chemotactic and pro-inflammatory profile, whereas BMDMs held a more pro-tumoural profile. However, a comparison of microglia between the tumour core and periphery revealed that tumour microglia upregulate many pro-tumoural genes, including multiple genes that have previously been defined as ‘BMDM-enriched’. Moreover, we found myeloid DEGs identified within the tumour core cluster to distinct spatial tumour regions such as the vascular or hypoxic niche. Immunohistochemical staining reflected these spatial expression profiles, identifying a distinct population of phagocytic macrophages within the hypoxic niche.

Conclusion

Although microglia and BMDMs represent two ontogenetically distinct myeloid populations within glioblastoma, both cell types can adopt similar functional expression profiles within the tumour core, particularly within tumour niches. This indicates that myeloid cell function is strongly influenced by the tumour microenvironment, rather than ontogeny alone.

P10.04.A The development of a potent, tumour-specific heptamethine cyanine dye-palbociclib conjugate with novel mechanisms of action for the treatment of glioblastoma

Background

Glioblastoma is the most common and aggressive primary brain tumour in adults. The development of anti-cancer agents for brain tumours is challenged by the blood-brain barrier and the resistance conferred by the local tumour microenvironment. Heptamethine cyanine dyes (HMCDs) are a class of near-infrared fluorescence compounds that have recently emerged as promising agents for drug delivery

Material and Methods

We conjugated palbociclib, a cyclin-dependent kinase 4/6 inhibitor to the HMCD, MHI 148 for the treatment of GBM. Patient-derived GBM cell lines were established from surgically resected biopsy GBM tissue.

Results

High-throughput drug screening revealed an almost 100-fold increase in cytotoxicity of the palbociclib-MHI 148 conjugate compared to palbociclib alone. Moreover, the palbociclib-MHI 148 conjugate was synergistic with radiation, but not with temozolomide. Further analysis revealed the palbociclib-MHI 148 conjugate was superior to other cyclin-dependent kinase inhibitors in vitro. The shift of palbociclib from cytostatic to cytotoxic when conjugated to MHI 148 prompted further investigation. We revealed that palbociclib-MHI 148-dependent inhibition of cell-cycle progression resulted in increased DNA damage. This preceded increased transcription of key extrinsic apoptosis genes and caused a time-dependent upregulation of TNFR1 endocytosis-dependent cell death signalling. Notably, inhibition of endocytosis and siRNA knockdown of TNFR1 prevented palbociclib-MHI 148-induced cell death.

Conclusion:

These results highlight a novel mechanism of action of palbociclib when conjugated to MHI-148 that induced autocrine-driven TNFR1-mediated apoptosis. In addition, we highlight the potential application of HMCDs in repurposing tyrosine kinase inhibitors, to overcome the current limitations preventing the expansion of second-line treatment options for GBM.

Differential Expression Patterns of Irf3 and Irf7 in Pediatric Lymphoid Disorders

Interferon regulatory factors (IRFs) are multifunctional transcriptional factors. To define the role of IRFs in lymphoid disorders, we determined the expression patterns of IRF3 and IRF7 by immunohistochemistry in 5 normal lymph nodes, 12 reactive hyperplastic lymph nodes, and 27 pediatric lymphomas. IRF3 was prominently expressed in the nuclei of the histiocytes, and was expressed very weakly in the cytoplasm of most of the lymphocytes of the normal lymph nodes. However, IRF7 was expressed strongly in the nuclei of over 50% of the lymphocytes throughout the normal lymph nodes, but the histiocytes and fibroblasts were spared. In the reactive hyperplastic lymph nodes, the number of IRF3- and IRF7-positive cells in the nuclei was elevated. In the lymphomas, the number of IRF3-positive cells in the nucleus appeared to have decreased, and the cells were scattered throughout the lymphoma tissue in no specific pattern. However, in most cases the number of IRF7-positive cells was elevated.

These results suggested that IRF3 was activated principally in the histiocytes and T cells under inflammatory conditions, but IRF3 activation was attenuated in cases of lymphoma. However, the number of IRF7-positive cells was found to be elevated in the reactive hyperplastic lymph nodes and pediatric lymphoma.

Polycyclic aromatic hydrocarbons in soils and crops after irrigation of wastewater discharged from domestic sewage treatment plants

The effects of domestic wastewater application on the translocation and accumulation of polycyclic aromatic hydrocarbons (PAHs) in soil and crops (rice, lettuce, and barley) were investigated by Wagner's pot experiment. In the soils and crops after domestic wastewater irrigation, high-molecular weight PAHs (5 to 6 ring) were not detected, but low-molecular weight PAHs (3 to 4 ring) were only detected at trace levels.

Microsatellite alteration in histologically normal lung tissue of patients with non-small cell lung cancer

Microsatellite alteration (MSA) has been observed in a fraction of non-small cell lung cancer (NSCLC). Most prior studies regarding MSA in lung cancer have usually used adjacent non-malignant lung tissues as a source of constitutional DNA. However, these normal tissues might have genetic alterations because the entire field of bronchial tree is exposed to the same carcinogenic insult. The aim of this study was to search if MSA is present in the histologically normal lung tissue of patients with NSCLC. Tumor and corresponding normal lung tissue specimens were obtained from 20 patients with NSCLC. Normal lung tissue specimens were obtained from either the opposite end of resected surgical samples or as distant from the tumor as possible. They were examined histopathologically and confirmed as normal by H-E stain. Patients' peripheral lymphocytes were used as the source for the normal DNA. Sixteen markers on 3p and 9p (nine and seven markers, respectively) were used. MSA was detected in seven of 20 (35%) histologically normal lung tissue specimens at a frequency similar to that observed in tumor tissue (eight of 20, 40%). Five cases showed MSA in both normal lung tissue and the corresponding tumor. In these five cases, MSA in normal lung tissue was detected at the same microsatellite markers which MSA was detected in the corresponding tumor. The number and size of novel bands in normal lung tissue was identical to that in tumor tissue except in one case. In which case, the same pattern of MSA was found in both normal lung tissue and corresponding tumor tissue at two markers. However, at one marker, while one identical novel band was detected in normal lung tissue and corresponding tumor tissue, another novel band was found only in tumor tissue. In two of 12 patients whose tumor was negative for the presence of MSA, MSA was detected in normal lung tissue. These results indicate that genetic alterations are widely distributed in the lung tissue of patients with lung cancer and provide considerable support for the field cancerization theory. Screening for MSA in resected normal lung tissue might be a new method to identify patients at high risk for developing second primary lung cancers.

Neural toxicity induced by accidental intrathecal vincristine administration

Described here is a case of accidental intrathecal administration of vincristine with pathologic findings in the central nervous system. A 3-year-old boy with acute lymphoblastic leukemia, was given his ninth course chemotherapy. Vincristine was accidentally injected intrathecally. The clinical course was rapidly progressive (6-day course) and resulted in death. An autopsy was done. The brain and spinal cord was grossly edematous and congested without any specific feature. Histologically, profound loss of neuron was noted in the spinal cord. Remaining neurons in the spinal cord, particularly anterior horn cells were markedly swollen. The spinal nerves show diffuse axonal degeneration and myelin loss. The upstream portion of the spinal cord (brain stem, cerebellum, cerebrum) showed patchy loss of neurons, especially Purkinje cells and granular cells of the cerebellar cortex. Many neurons showed axonal reaction (chromatolysis) with swelling. Several neurons show intracytoplasmic eosinophilic inclusion body. Myelin loss, axonal swelling and enlargement of perivascular spaces were seen throughout the white matter of central nervous system.