The Beavis laboratory has a focus on developing novel immune-based therapies for Cancer. We employ innovative approaches and technologies to enhance the effectiveness of both conventional immunotherapies and chimeric antigen receptor (CAR) T cells in the treatment of solid cancers such as breast cancer and melanoma.
Immunotherapy of cancer has been a major breakthrough in the last decade, now being accepted as the fourth pillar of cancer treatment after surgery, chemotherapy and radiotherapy. Immunotherapy is most effective in cancers with a high mutational burden, while cancers with a low mutational burden are refractory. Our research focus is to identify novel targets/ combination approaches that are effective in these refractory cancers.
Targeting adenosine mediated immunosuppression
Tumours utilise multiple immunosuppressive pathways to suppress anti-tumour immune responses including well characterised immune checkpoints such as the PDL-1: PD-1 axis. One such mechanism is the production of adenosine by tumour cells and host immunosuppressive cells (Beavis et al. 2012), catalysed by the ectoenzyme CD73 (Figure 1). Our work has shown that expression of CD73 is a prognostic biomarker in cancer patients and has highlighted the significant role of adenosine in the tumour-mediated immunosuppression of NK cells (Beavis et al. 2013) and T cells (Beavis et.al. 2015). Adenosine suppresses the anti-tumour activity of NK cells and T cells principally through binding to adenosine A2A receptors, expressed following activation of these cells. Importantly, we led the way in revealing that blockade of A2A receptors increases the effectiveness of PD-1 blockade (Beavis et al. 2015).
Several pharmaceutical companies have now developed antibodies and/or small molecule inhibitors of the CD73-A2A axis and these are now in phase I clinical trials, including two phase I clinical trials that are being conducted at the Peter MacCallum Cancer Centre. Current work in this area is focused upon further characterising the mechanism by which A2A antagonists are effective at both the cellular and molecular level. We believe this will result in the identification of novel combination therapies, with the potential to further enhance the effectiveness of targeting this pathway in cancer patients.
Figure 1: Generation of adenosine in the tumor microenvironment, driven by ectoenzymes CD39 and CD73, leads to the suppression of multiple immune subsets.
Enhancing the efficacy of chimeric antigen receptor (CAR) T cells in solid tumours
The generation of Chimeric Antigen Receptor (CAR) T cells involves the transduction of a patient’s peripheral blood derived-T cells with a CAR that is able to directly recognise tumour antigens on the cell surface and infusing these back into the patient. CAR T cells have been proven to be highly effective in haematological malignancies and are now FDA approved.
In the Beavis laboratory, we are focused upon enhancing the effectiveness of CAR T cells in solid cancers since results in this setting have so far failed to recapitulate the striking successes seen in haematological cancers. The major themes of our research are to develop innovative strategies to overcome 1) Local immunosuppression of CAR T cells 2) Heterogeneity of tumour antigen expression and 3) Poor trafficking of CAR T cells to the solid tumours (Figure 2).
Figure 2: Research themes in the Beavis lab to enhance the efficacy of CAR T cell therapy
Theme 1: Local immunosuppression of CAR T cells
It has now been established that CAR T cells are subject to the same immunosuppressive mechanisms which limit the anti-tumour activity of conventional T cells. Our group was the first to show that targeting the adenosine A2A receptor could significantly enhance the efficacy of CAR T cells in solid tumours, particularly in combination with anti-PD-1 (Beavis et al. 2017). We are currently pursuing other targets that can enhance CAR T cell function by relieving tumour-induced immunosuppression and have developed CRISPR/Cas9 technology to achieve this.
Theme 2: Engaging endogenous immunity to overcome antigen heterogeneity
A major obstacle to the success of CAR T cells in solid tumours is the heterogeneous expression of tumour antigens which can lead to relapse after treatment with tumour cells negative for the CAR antigen. Therefore our philosophy is that CAR T cells need to engage the endogenous immune system to be successful in treating solid tumours. Our recent work (Lai, Mardiana et al. 2020) has demonstrated that T cells engineered to secrete Fms-like tyrosine kinase 3 Ligand (Flt3L) can induce the proliferation of host dendritic cells, particularly conventional type I DCs (cDC1); a subset specialised in the cross-presentation of tumour antigens to activate host CD8+ T cells. Importantly, we showed the combination Flt3L armoured CAR T cells and immune stimulatory adjuvants can drive significant host CD8+ T cell epitope spreading to target non-CAR antigens (Figure 3). This work holds translational potential for enhancing CAR T cell therapeutic efficacy in clinical settings of solid cancers with heterogeneous tumour antigen expression.
Figure 3. a. Graphical illustration of Flt3L armoured CAR T cell therapy. CAR T cells target antigen-positive tumours and secrete Flt3L into tumours. Flt3L expands and recruits cDC1, which upon activation with immune adjuvants, increase the activation of host CD8+ T cells in the tumour draining lymph node. This enhances the proportion of host anti-tumour CD8+ T cells, which are able to target antigen-negative tumour variants. b. Adoptive transfer of T cells engineered to express Flt3L induces the oligoclonal expansion of host T cells. c. Treatment of E0771-OVA-Her2 tumor-bearing mice with Flt3L-secreting anti-Her2 CAR T cells and immune adjuvants significantly increase the number of host CD8+ T cells targeting non-CAR (OVA Tetramer+) antigens (Data from Lai, Mardiana et al. 2020).
Theme 3: Enhancing T cell trafficking
One of the major limitations of currently approved immunotherapies is that they are ineffective in patients where an immune cell infiltrate into the tumour is lacking (so called ‘cold’ tumours). We have recently demonstrated that the chemoattractant cytokines (chemokines) CXCL9 and CXCL10 are essential for the trafficking of T cells to the tumour site and, in turn, the therapeutic efficacy of immune check point blockade (Figure 4; House et al., 2020 Featured on the cover of Clin. Cancer Res.). It is for this reason that in the Beavis lab we are currently developing novel strategies designed to enhance immune cell trafficking into tumours. We have developed high-throughput strategies to identify gene targets and therapeutics to enhance T cell trafficking. We have now combined this work with our significant experience in CAR T cell biology to develop highly innovative strategies to reprogram the tumour microenvironment and promote both CAR and endogenous T cell trafficking to the tumour. This project has the potential to discover novel targets that could significantly enhance the effectiveness of immunotherapy in solid cancers.
Figure 4. A. Differential gene expression analysis comparing responders to non-responders in baseline biopsies from melanoma patients receiving combination nivolumab/pembrolizumab and ipilimumab. B CXCR3 blockade inhibits the therapeutic efficacy of dual anti-PD-1 and anti-CTLA-4 (P+C). C. T cell infiltrate in tumours was assessed 7 days post-therapy ± anti-CXCR3 by immunofluorescence staining. Data from House et al. 2020, Clinical Cancer Research.
Theme 4: Clinical Translation
The Peter Mac is a world leader in the CAR T cell field and was the first centre in Australia to run a CAR T cell clinical trial. Clinical trials investigating CAR T cells in solid cancers are ongoing at the Peter Mac (PI Ben Solomon, funded by Celgene-Bristol-Myers-Squibb) targeting the Lewis Y antigen. The Peter Mac is the home of the National Centre of Excellence in Cellular Immunotherapies, developed to provide world-leading discoveries in CAR T-cell and cellular immunotherapy. Therefore our research in this area has high potential for future translation.
1. Junyun Lai*, Sherly Mardiana*, Imran G. House, Kevin Sek, Melissa A. Henderson, Lauren Giuffrida, Amanda X. Y. Chen, 12 Kirsten L. Todd, Emma V. Petley, Jack D. Chan, Emma M. Carrington, Andrew M. Lew, Benjamin J. Solomon, Joseph A. 13 Trapani, Katherine Kedzierska, Maximilien Evrard, Stephin J. Vervoort, Jason Waithman, Phillip K. Darcy and Paul A. Beavis (2020) Adoptive cellular therapy with T cells expressing the dendritic cell growth factor Flt3L drives epitope spreading and antitumor immunity. Nat. Immunol. *these authors contributed equally.
This work revealed that engineering CAR T cells to secrete Flt3L could drive dendritic cell mediated epitope spreading and effective targeting of antigen negative tumours.
2. Imran G. House, Peter Savas, Junyun Lai, Amanda X.Y. Chen, Amanda J. Oliver, Zhi L. Teo, Kirsten L. Todd, Melissa A. Henderson, Lauren Giuffrida, Emma V. Petley, Kevin Sek, Sherly Mardiana, Tuba N. Gide, Camelia Quek, Richard A. Scolyer, Georgina V. Long, James S. Wilmott, Sherene Loi, Phillip K. Darcy and Paul A. Beavis. (2020) Macrophage-Derived CXCL9 and CXCL10 Are Required for Antitumor Immune Responses Following Immune Checkpoint Blockade. Clin. Cancer Res 2020;26:487–504
This work revealed that the chemokines CXCL9 and CXCL10 are critical for the efficacy of conventional immunotherapies.
3. Sherly Mardiana, Benjamin J. Solomon, Phillip K. Darcy1*, and Paul A. Beavis* (2019) Supercharging adoptive T cell therapy to overcome solid tumor–induced immunosuppression. Science Trans. Med. Vol. 11, Issue 495, eaaw2293 *these authors contributed equally to this work.
A recent invited review of the CAR T cell field.
4. Beavis PA, Henderson MA, Giuffrida L, Davenport AJ, Petley EV, House IG, Lai J, Sek K, Milenkovski N, John LB, Mardiana S, Slaney CY, Trapani JA, Loi S, Kershaw MH, Haynes NM and Darcy PK (2018) Dual PD-1 and CTLA-4 checkpoint blockade promotes antitumor immune responses through CD4+Foxp3– cells that modulate CD103+ dendritic cells. Cancer Immunol Res. 2018 Sep;6(9):1069-1081
This work revealed a novel interaction between CD4+ effector cells and a dendritic cell subtype that was critical for responses to immune checkpoint blockade.
5. Beavis PA, Henderson MA, Giuffrida L, Mills JK, Sek K, Cross RS, Davenport AJ, John LB, Mardiana S, Slaney CY, Johnstone RW, Trapani JA, Stagg J, Loi S, Kats L, Gyorki D, Kershaw MH, Darcy PK (2017) Targeting the adenosine 2A receptor enhances chimeric antigen receptor T cell efficacy. J Clin Invest. 127(3) 929-941.
This work showed that targeting the A2AR could enhance CAR T cell function in solid tumours.
6. Mardiana S, John LB, Henderson MA, Slaney CY, von Scheidt B, Giuffrida L, Davenport AJ, Trapani JA, Neeson PJ, Loi S, Haynes NM, Kershaw MH, Beavis PA* Darcy PK*. (2017) A Multifunctional Role for Adjuvant Anti-4-1BB Therapy in Augmenting Antitumor Response by Chimeric Antigen Receptor T Cells. Cancer Res. 77(6) 1296-1309. *Co-senior authors.
This study showed that anti-41BB could enhance CAR T cell function by engaging the endogenous immune response.
7. Dushyanthen S, Teo ZL, Caramia F, Savas P, Mintoff CP, Virassamy B, Henderson MA, Luen SJ, Mansour M, Kershaw MH, Trapani JA, Neeson PJ, Salgado R, McArthur GA, Balko JM, Beavis PA*, Darcy PK*, Loi S*. (2017) Agonist immunotherapy restores T cell function following MEK inhibition improving efficacy in breast cancer. Nat Commun. 8(1) 606. *Co-senior authors.
This study highlights the relationship between RAS-MAPK-MEK siganalling and the reduced immunogenicity of tumour cells leading to reduced immune cell infiltrate. A combination of a MEK inhibitor and immune agonist therapy was shown to enhance anti-tumour immune responses.
8. Beavis PA, Milenkovski N, Henderson MA, John LB, Allard B, Loi S, Kershaw MH, Stagg J, Darcy PK. (2015) Adenosine Receptor 2A Blockade Increases the Efficacy of Anti-PD-1 through Enhanced Antitumor T-cell Responses. Cancer Immunol Res. 3(5) 506-517.
This highly cited publication showed that A2AR blockade could enhance the therapeutic efficacy of anti-PD-1. Subsequently, this combination therapy has progressed to clinical trials at multiple sites including the Peter MacCallum Cancer Centre.
9. Beavis PA, Divisekera U, Paget C, Chow MT, John LB, Devaud C, Dwyer K, Stagg J, Smyth MJ, Darcy PK. (2013) Blockade of A2A receptors potently suppresses the metastasis of CD73+ tumors. Proc. Natl Acad Sci USA 110(36) 14711-6.
This highly cited publication showed that A2AR and A2BR blockade could reduce tumour metastasis.
10. Beavis PA, Stagg J, Darcy PK, Smyth MJ. (2012) CD73: a potent suppressor of antitumor immune responses. Trends Immunol 33(5) 231-7.
This review covers the immunosuppressive CD73-adenosine axis and its relevance to cancer.