Proffered papers session (Prize winners)


Programme session type(s): Proffered papers session

11:00-12:30

Room: Carron

Polyphenols Act Synergistically with Doxorubicin and Etoposide in Leukemia Cell Lines.
Speaker: Amani Mahbub
Affiliation: Umm Al Qura University

Abstract:

The study aimed to assess the effects of polyphenols when used in combination with doxorubicin and etoposide, and to determine whether polyphenols sensitised leukaemia cells, causing induction of apoptosis. Quercetin, apigenin, emodin, rhein and cis-stilbene were investigated alone and in combination with etoposide and doxorubicin in two lymphoid and two myeloid leukaemia cells lines.

Method

Measurements were made of ATP levels using CellTiter-Glo assay as an indication of total cell number, cell cycle progression using PI staining and flow cytometry, and apoptosis by NucView caspase 3 assay and Hoechst 33342/PI staining. Effects of combination treatments on caspases 3, 8 and 9 activity were determined using Glo luminescent assays, glutathione levels were measured using the GSH-Glo Glutathione Assay and DNA damage determined by anti-γH2AX staining.

Results

Doxorubicin and etoposide in combination with polyphenols synergistically reduced ATP levels, induced apoptosis and arrested S and/or G2/M phases in lymphoid cell lines. However, in the myeloid cell lines the effects of the combination treatments varied; doxorubicin had a synergistic or additive effect when combined with quercetin, apigenin, emodin, and cis-stilbene, but had an antagonistic effect when combined with rhein. Combination treatment caused a synergistic downregulation of glutathione levels and increased DNA damage, driving apoptosis via caspase 8 and 9 activation. However, in myeloid cells where antagonistic effects were observed, this was associated with increased glutathione levels and a reduction in DNA damage and apoptosis.

Conclusion

In conclusion, doxorubicin and etoposide activity can be enhanced by polyphenols, particularly in lymphoid leukaemia cells, although effects were strongly dependent on type of cell line, with some interactions were antagonistic in myeloid cell lines.

Molecular mechanisms underlying phenotypic plasticity in malignant glioma
Speaker: Costanza Lo Cascio
Affiliation: Barrow Neurological Institute

Abstract:

Glioblastoma (GBM) is characterized by rapidly proliferating and invasive cells that infiltrate normal brain regions. Following exposure to aggressive treatment regimens, GBMs frequently shift their biological features upon recurrence, acquiring a more resistant phenotype. However, the dynamics and molecular mechanisms that facilitate GBM recurrence are still poorly understood. Considering the unchanged dismal prognosis for GBM patients, there is a need to understand, at a systems level, how plastic processes (molecular switches) in glioma stem-like cells (GSCs) may drive tumor maintenance and cancer cell adaptability in GBM. The objective our study was to determine how GSCs temporally adjust their expression profile and phenotype in response to ionizing radiation in vitro and in vivo using patient-derived xenograft (PDX) models of GBM.

Method

We established PDX GBM models by intracranially implanting two patient-derived GSC lines belonging to different GBM molecular subgroups into immunocompromised mice. The tumor-bearing mice were treated with single doses of ionizing radiation to assess acute responses to treatment. Mice from each cohort were be sacrificed at multiple distinct time points following treatment. Using immunohistochemical methods, we assessed changes in the expression of GBM subclass markers, stemness and differentiation markers, and DNA damage/repair proteins across the entire tumor population over time. To understand how GSCs respond to radiation at a molecular level, we employed mass cytometry (CyTOF) and RNA-seq to determine how important cellular signaling pathways and transcriptional programs necessary for GSC self-renewal, invasion and growth are altered at various time points post-treatment.

Results

We demonstrate that GSCs, both in vitro and in vivo, undergo an immediate response following exposure to radiation that results in a global modulation of the expression of key stemness and proliferation genes under adverse conditions.

Conclusion

Our results suggest that this acute response allows GSCs to enter a transient semi-differentiated state that favors GSC adaptability and resistance to therapy

From rarity to clarity: gd T cells in cancer
Speaker: Seth Coffelt
Affiliation: Beatson Institute for Cancer Research

Abstract:

Over the past 10 years, the cancer community has learned a great deal about how solid tumors alter distant organs to create a suitable environment for the seeding and outgrowth of disseminated cancer cells. Immune cells are major contributors to this process, where some populations work to counteract metastasis and other populations function to promote metastasis. We have shown that gd T cells – a rare population of T cell receptor-expressing cells that straddle the line between innate and adaptive immunity – advance mammary tumour metastasis through expression of IL-17. We have found that IL-17-producing gd T cells instruct neutrophils to suppress the function of CD8 T cells, allowing metastatic cancer cells to avoid anti-tumour immunity. My lab is now interested in understanding how IL-17-producing gd T cells are regulated in the pre-metastatic niche of the lung, in order to develop novel immunotherapies that counteract their function and reduce mammary tumour metastasis. At the same time, we are exploring the role of gd T cells in other cancer types, including colorectal cancer and pancreatic cancer. We are particularly interested in liver-resident gd T cells and how they may shape this major site of metastasis. During my talk, I will present our latest data in this area, which are providing clarity on the function of gd T cells in different metastatic organs.

Antibody Tumour Targeting Is Enhanced by CD27 Agonists through Myeloid Recruitment
Speaker: Sean Lim
Affiliation: University of Southampton

Abstract:

Tumour-targeting monoclonal antibodies (mAb) such as anti-CD20 exert their anti-tumour activity through macrophage-mediated antibody-dependent cellular phagocytosis (ADCP).  We examined whether the efficacy of CD20 mAb could be augmented by combination with immunomodulatory mAbs against PD-1, CTLA-4, OX40, GITR, and CD27.  CD27 is a TNFR superfamily member expressed constitutively on T and NK cells and has been shown to regulate CD8+ T-cell priming, cytotoxicity, and memory responses.

Method

mAb combinations were tested in multiple immunocompetent murine B-cell lymphoma models (BCL1, A31 and Em-TCL1) and in human CD27 transgenic mice.  We dissected the mechanism of action of the mAbs through single-cell RNA sequencing and functional immunological assays.

Results

Amongst the immunomodulatory mAb tested with anti-CD20, only addition of an agonistic mAb against CD27 markedly improved the survival of BCL1 lymphoma-bearing mice.  Similar results were observed in multiple B-cell lymphoma models.

Profound myeloid cell infiltration and activation was observed in mice treated with anti-CD27.  mRNA expression of known myeloid chemoattractants (CCL3, CCL4 and CCL5) and IFNg was observed on CD8+ T cells.  In vivo neutralisation of IFNg or depletion of T and NK cells, abrogated myeloid cell infiltration by anti-CD27.  Further, macrophages from anti-CD27 treated mice demonstrated increased phagocytic ability in the presence of anti-CD20.

Conclusion

These data demonstrate the therapeutic potential of combining a tumour-targeting mAb with an immunostimulating mAb, through a hitherto, unexpected mechanism of action involving activation of the innate immunity.  Here, anti-CD27 indirectly increased the capacity of macrophages to perform anti-CD20-mediated ADCP through T-cell activation. Based upon these data, a U.K. multicentre phase II clinical trial examining rituximab and varlilumab (anti-CD27) in relapsed and/or refractory B-cell lymphoma has been initiated (RIVA trial NCT03307746).

Circulating tumour DNA as a tool to guide clinical decision making in melanoma
Speaker: Rebecca Lee
Affiliation: CRUK MI

Abstract:

Immunotherapy and targeted therapy have revolutionised outcomes for patients with metastatic melanoma, however there remain patients who are refractory to treatment or who develop resistance. Tools are therefore required to identify patients at high risk of progression and to detect emerging resistance early so personalised treatment options can be explored. Circulating tumour DNA (ctDNA) can be used to monitor response to therapy, identify mechanisms of resistance and be used as a prognostic biomarker. We aimed to understand how ctDNA could be used to inform clinical decision making for patients with melanoma.

Method

Patients treated at The Christie hospital underwent longitudinal blood sampling for ctDNA. Following extraction of cell free DNA from plasma, we performed whole exome and targeted sequencing to identify mutations. Furthermore, we carried out droplet digital polymerase chain reaction to detect BRAF and NRAS mutations in plasma taken after surgery from 161 stage II/III high-risk melanoma patients enrolled in the AVAST-M adjuvant trial.

Results

Levels of circulating tumour DNA mirrored response in patients undergoing treatment for melanoma. We identified mutations associated with resistance to therapy in patients with disease progression on targeted therapy. Detectable ctDNA within 12 weeks of surgery for stage II/III melanoma was associated with inferior disease-free, distant-metastatic free and overall survival. Based on these results we have designed two trials; CirculAting Tumour DNA gUided therapy Switch (CAcTUS) and Circulating tumour DNA guidEd Therapy for stage IIB/C BRAF or NRAS mutant- positive mElanoma after surgiCal resecTION (DETECTION).

Conclusion

CtDNA is a useful tool to monitor treatment response and to characterise mechanisms of resistance to therapies for melanoma. Furthermore it can be used to predict relapse and survival of patients at high risk of disease progression following curative intent surgery. Clinical trials are ongoing to assess the impact of ctDNA-guided decision-making on patient outcomes.