Immunoscore is a measure of the presence of activated immune cells within a tumour as defined by the Union Internationale Contre le Cancer . Immune checkpoint inhibitors are generally not effective against tumours with a low mutational burden and low (“cold”) immunoscores. By contrast tumours such as melanoma for which immune checkpoint inhibitors are highly effective have a high (“hot”) immunoscore.
Pancreatic cancer and other solid tumours have been described to have a “cold” immunoscore which correlates with the failure of immune checkpoint inhibitors to be effective . In addition a “cold” or actively immunosuppressive solid tumour microenvironment also inhibits the mechanism of action of the class of immunotherapeutics known as CAR-T which are effective for haematological cancers.
Understanding the molecular basis of the “cold” pancreatic cancer immunoscore and developing agents that can “heat-up” pancreatic cancer is essential in order to manufacture effective immunotherapeutic treatments for this disease.
- Galon J, Mlecnik B, Bindea G, Angell HK, Berger A, Lagorce C, Lugli A, Zlobec I, Hartmann A, Bifulco C, Nagtegaal ID, Palmqvist R, Masucci GV, Botti G, Tatangelo F, Delrio P, Maio M, Laghi L, Grizzi F, Asslaber M, D’Arrigo C, Vidal-Vanaclocha F, Zavadova E, Chouchane L, Ohashi PS, Hafezi-Bakhtiari S, Wouters BG, Roehrl M, Nguyen L, Kawakami Y, Hazama S, Okuno K, Ogino S, Gibbs P, Waring P, Sato N, Torigoe T, Itoh K, Patel PS, Shukla SN, Wang Y, Kopetz S, Sinicrope FA, Scripcariu V, Ascierto PA, Marincola FM, Fox BA, Pagès F. Towards the introduction of the ‘Immunoscore’ in the classification of malignant tumours. J Pathol. 2014 Jan;232(2):199-209. doi: 10.1002/path.4287. Review. PubMed PMID: 24122236.
Heat killed Mycobacterium obuense is claimed to stimulate Th1 immune response against tumours and down regulate Th2 responses . It acts as a Pathogen-Associated Molecular Pattern (PAMP) acting on γδ T-cells, granulocytes, and antigen-presenting cells (such as dendritic cells) [2, 3]. Intradermally delivered Mycobacterium obuense has recently undergone a phase II clinical trial in advanced pancreatic cancer patients demonstrating safety and showed promising signs of efficacy that need to be confirmed in a phase III clincal trial . A systemic immune activation against pancreatic cancer is promising as these tumours are difficult for the clinician to manipulate/ manually inject.
- Charles Akle Satvinder Mudan John Grange (2013). Cancer therapy, US patent US13396866 , 2013-12-31 .
- Fowler DW, Copier J, Wilson N, Dalgleish AG, Bodman-Smith MD. Mycobacteria activate γδ T-cell anti-tumour responses via cytokines from type 1 myeloid dendritic cells: a mechanism of action for cancer immunotherapy. Cancer Immunol Immunother. 2012 Apr;61(4):535-47. doi: 10.1007/s00262-011-1121-4. PubMed PMID: 22002242.
- Bazzi S, Modjtahedi H, Mudan S, Akle C, Bahr GM. Analysis of the immunomodulatory properties of two heat-killed mycobacterial preparations in a human whole blood model. Immunobiology. 2015 Dec;220(12):1293-304. doi: 10.1016/j.imbio.2015.07.015. PubMed PMID: 26253276.
- Dalgleish AG, Stebbing J, Adamson DJ, Arif SS, Bidoli P, Chang D, Cheeseman S, Diaz-Beveridge R, Fernandez-Martos C, Glynne-Jones R, Granetto C, Massuti B, McAdam K, McDermott R, Martín AJ, Papamichael D, Pazo-Cid R, Vieitez JM, Zaniboni A, Carroll KJ, Wagle S, Gaya A, Mudan SS. Randomised, open-label, phase II study of gemcitabine with and without IMM-101 for advanced pancreatic cancer. Br J Cancer. 2016 Sep 27;115(7):789-96. doi: 10.1038/bjc.2016.271. PubMed PMID: 27599039
Nelfinavir trade name Viracept (Pfizer) was approved by the FDA in 1997 as a human immunodeficiency virus (HIV) therapeutic. It’s anti-HIV mechanism of action is based upon inhibiting the virus’ aspartate protease . HIV protease inhibitors including Nelfinavir have been demonstrated to inhibit the Akt pathway of cancer cell lines including pancreatic and sensitise mouse tumour xenografts to radiation therapy . Nelfinavir inhibits in vivo tumor model growth and upregulates markers of ER stress, autophagy and apoptosis . Cell death mediated by autophagy and ER stress (immunogenic cell death) is associated with immune responses against cancer .
Nelfinavir has entered a number of clinical trials for pancreatic cancer with, so far, promising but statistically low power results .
Clinical Trials .gov links
NCT01068327, NCT01959672, NCT01086332, NCT02024009
EU Clinical Trials Register links
- Koltai T. Nelfinavir and other protease inhibitors in cancer: mechanisms involved in anticancer activity. Version 2. F1000Res. 2015 Jan 12 [revised 2015 Jan 1];4:9. Doi: 10.12688/f1000research.5827.2. Review. PubMed PMID: 26097685.
- Gupta AK, Cerniglia GJ, Mick R, McKenna WG, Muschel RJ. HIV protease inhibitors block Akt signaling and radiosensitize tumor cells both in vitro and in vivo. Cancer Res. 2005 Sep 15;65(18):8256-65. PubMed PMID: 16166302.
- Gills JJ, Lopiccolo J, Dennis PA. Nelfinavir, a new anti-cancer drug with pleiotropic effects and many paths to autophagy. Autophagy. 2008 Jan;4(1):107-9. PubMed PMID: 18000394.
- Hou W, Zhang Q, Yan Z, Chen R, Zeh Iii HJ, Kang R, Lotze MT, Tang D. Strange attractors: DAMPs and autophagy link tumor cell death and immunity. Cell Death Dis. 2013 Dec 12;4:e966. doi: 10.1038/cddis.2013.493. Review. PubMed PMID: 24336086.
- Wilson JM, Fokas E, Dutton SJ, Patel N, Hawkins MA, Eccles C, Chu KY, Durrant L, Abraham AG, Partridge M, Woodward M, O’Neill E, Maughan T, McKenna WG, Mukherjee S, Brunner TB. ARCII: A phase II trial of the HIV protease inhibitor Nelfinavir in combination with chemoradiation for locally advanced inoperable pancreatic cancer. Radiother Oncol. 2016 May;119(2):306-11. Doi: 10.1016/j.radonc.2016.03.021. PubMed PMID: 27117177.
Pancreatic ductal adenocaricoma (PDAC) is characterised by a dense desmoplastic stroma. It has become increasingly appreciated that in order to effectively treat pancreatic cancer both the tumour stroma and the cancer cells themselves must be targeted. The pancreatic cancer microenvironment has broad immunosuppressive and metastatic promoting properties mediated by many of the stroma resident cells including M2 polarised macrophages.
M2 macrophages secrete TGF-β1 which is known to mediate epithelial to mesenchymal transition (EMT) of pancreatic cancer cells yielding stem-like cell properties including enhanced resistance to the chemotherapeutic gemcitabine. A recent paper found that it was possible to inhibit TGF-β1 secretion by macrophages in vitro and that this restored sensitivity of pancreatic cancer cell lines to gemcitabine .
Primary tumour associated macrophages (TAMs) were generated from mononuclear cells obtained from the peripheral blood of volunteers by culturing differentiated macrophages with pancreatic cancer cell line conditioned cell culture media. It was found that TAM conditioned media contained significantly more TGF-β1 than conditioned media from normal macrophages.
Statins are a class of cholesterol lowering drugs that act by inhibiting the enzyme HMG-CoA reductase. Treatment of the TAMs with the statin Simvastatin reduced TGF-β1 secretion. Conditioned media from Simvastatin treated TAMs allowed greater killing of pancreatic cancer cell lines upon gemcitabine application than untreated TAM conditioned media. This was probably due to a decreased cancer cell EMT phenotype in the Simvastatin treatment arm. This study showed in vitro that statins have potential applications for pancreatic cancer therapy by reducing the ability of the microenvironment to produce chemotherapy resistant pancreatic cancer cells.
- Xian G, Zhao J, Qin C, Zhang Z, Lin Y, Su Z. Simvastatin attenuates macrophage-mediated gemcitabine resistance of pancreatic ductal adenocarcinoma by regulating the TGF-β1/Gfi-1 axis. Cancer Lett. 2016 Nov 10. Pii: S0304-3835(16)30684-X. doi: 10.1016/j.canlet.2016.11.006. PubMed PMID: 27840243.
Pancreatic tumours containing immunosuppressive M2 tumour associated macrophages (TAMs) have a poor prognosis . TAMs are derived from circulating inflammatory monocytes both of which express the CCR2 chemokine receptor. Pancreatic tumours are known to express CCL2 – the CCR2 ligand. In mouse models of pancreatic cancer it has been found that inhibition of CCR2 inhibits M2 TAM infiltration into the tumour microenvironment . M2 TAMs are one of the reasons immune checkpoint inhibitor antibodies are not effective as a single agent therapy for pancreatic cancer. Combinations of checkpoint inhibitors with CCR2 inhibitors are therefore of future interest if single agent CCR2 inhibition proves safe and effective in pancreatic cancer clinical trials.
A phase I clinical trial with a CCR2 inhibitor in combination with the chemotherapy FOLFIRINOX in patients with borderline resectable and locally advanced pancreatic cancer demonstrated that CCR2 inhibition prevented inflammatory monocyte migration from the bone marrow and decreased the number of TAMs in the tumour microenvironment . It also demonstrated that combination with FOLFIRINOX was safe and tolerable.
The following pancreatic cancer clinical trials for agents targeting CCR2 are active:
- Kurahara, Hiroshi, Hiroyuki Shinchi, Yuko Mataki, Kousei Maemura, Hidetoshi Noma, Fumitake Kubo, Masahiko Sakoda, Shinichi Ueno, Shoji Natsugoe, and Sonshin Takao. ‘Significance of M2-Polarized Tumor-Associated Macrophage in Pancreatic Cancer’. The Journal of Surgical Research 167, no. 2 (15 May 2011): e211–19. PMID: 19765725.
- Sanford DE, Belt BA, Panni RZ, Mayer A, Deshpande AD, Carpenter D, Mitchem JB, Plambeck-Suess SM, Worley LA, Goetz BD, Wang-Gillam A, Eberlein TJ, Denardo DG, Goedegebuure SP, Linehan DC. Inflammatory monocyte mobilization decreases patient survival in pancreatic cancer: a role for targeting the CCL2/CCR2 axis. Clin Cancer Res. 2013 Jul 1;19(13):3404-15. doi: 10.1158/1078-0432.CCR-13-0525. PubMed PMID: 23653148.
- Nywening TM, Wang-Gillam A, Sanford DE, Belt BA, Panni RZ, Cusworth BM, Toriola AT, Nieman RK, Worley LA, Yano M, Fowler KJ, Lockhart AC, Suresh R, Tan BR, Lim KH, Fields RC, Strasberg SM, Hawkins WG, DeNardo DG, Goedegebuure SP, Linehan DC. Targeting tumour-associated macrophages with CCR2 inhibition in combination with FOLFIRINOX in patients with borderline resectable and locally advanced pancreatic cancer: a single-centre, open-label, dose-finding, non-randomised, phase 1b trial. Lancet Oncol. 2016 May;17(5):651-62. Doi: 10.1016/S1470-2045(16)00078-4. PubMed PMID: 27055731.
CXCR2 and CXCR4 cytokine receptors are known to be expressed by immune inhibitory cells such as neutrophils, myeloid derived suppressor cells (MDSCs), and Tregs. Cytokine signalling from the pancreatic cancer microenvironment attracts these cells which then prevent CD8+ and CD4+ T cells from engaging with the tumour. It has been found that targeting the CXCR2 and CXCR4 signalling axis in mouse models of pancreatic cancer can make checkpoint inhibitor therapy effective which, unfortunately, normally does not reduce pancreatic tumour volume due to the inhibitory microenvironment [1,2].
The following CXCR4 and CXCR2 clinical trials may be of relevance to pancreatic cancer:
NCT02179970, NCT02823405, NCT01480739.
- Steele, Colin W., Saadia A. Karim, Joshua D.G. Leach, Peter Bailey, Rosanna Upstill-Goddard, Loveena Rishi, Mona Foth, et al. ‘CXCR2 Inhibition Profoundly Suppresses Metastases and Augments Immunotherapy in Pancreatic Ductal Adenocarcinoma’. Cancer Cell, June 2016. doi:10.1016/j.ccell.2016.04.014.
- Feig C, Jones JO, Kraman M, Wells RJ, Deonarine A, Chan DS, Connell CM, Roberts EW, Zhao Q, Caballero OL, Teichmann SA, Janowitz T, Jodrell DI, Tuveson DA, Fearon DT. Targeting CXCL12 from FAP-expressing carcinoma-associated fibroblasts synergizes with anti-PD-L1 immunotherapy in pancreatic cancer. Proc Natl Acad Sci U S A. 2013 Dec 10;110(50):20212-7. doi: 10.1073/pnas.1320318110. PubMed PMID: 24277834.
Celastrol is a triterpenoid compound (figure 1) which can be produced from the leaves of a plant used in traditional Chinese medicine called Tripterygium wilfordii or 雷公藤 . Celastrol prevents interaction between HSP90 and its cochaperone CDC37. It has no effect on ATP binding to HSP90 which most other inhibitors target .
HSP90s are a family of chaperone proteins that function to stabilise, regulate and activate a range of so called client proteins . The particular subset of client proteins they interact with is determined by the cochaperone. CDC37 facilitates the interaction of HSP90 with a number of kinases with important functions in cancer such as SRC, RAF1 and AKT .
Treatment of the cancer cell line Panc-1 with Celastrol induced apoptosis, reduced the tumour volume of Panc-1 mouse xenografts and increased the survival time of mice bearing those xenografts . Clinical trials using other single agent HSP90 inhibitors for pancreatic cancer have not been successful to date [5,6]. However combination strategies that target chemotherapeutic agents via conjugation to HSP90 inhibitors and HSP90 inhibitor incorporation into nanoparticles are under development which may be more effective [7,8].
- William T. Chalmers James P. Kutney Phillip J. Salisbury Kenneth L. Stuart Phillip M. Townsley Brian R. Worth (1982). Method for producing tripdiolide, triptolide and celastrol, US patent US4328309A. 1982-05-04.
- Zhang T, Hamza A, Cao X, Wang B, Yu S, Zhan CG, Sun D. A novel Hsp90 inhibitor to disrupt Hsp90/Cdc37 complex against pancreatic cancer cells. Mol Cancer Ther. 2008 Jan;7(1):162-70. doi: 10.1158/1535-7163.MCT-07-0484. PubMed PMID: 18202019.
- Pearl LH. Review: The HSP90 molecular chaperone-an enigmatic ATPase. Biopolymers. 2016 Aug;105(8):594-607. doi: 10.1002/bip.22835. Review. PubMed PMID: 26991466.
- Pearl LH. Hsp90 and Cdc37 — a chaperone cancer conspiracy. Curr Opin Genet Dev. 2005 Feb;15(1):55-61. Review. PubMed PMID: 15661534.
- PhII Study STA-9090 as Second or Third-Line Therapy for Metastatic Pancreas Cancer. ClinicalTrials.gov Identifier NCT01227018
- Study of AUY922 in Metastatic Pancreatic Cancer Who Are Resistant to First Line Chemotherapy. ClinicalTrials.gov Identifier: NCT01484860
- Bobrov E, Skobeleva N, Restifo D, Beglyarova N, Cai KQ, Handorf E, Campbell K, Proia DA, Khazak V, Golemis EA, Astsaturov I. Targeted delivery of chemotherapy using HSP90 inhibitor drug conjugates is highly active against pancreatic cancer models. Oncotarget. 2016 Oct 13. doi: 10.18632/oncotarget.12642. PubMed PMID: 27779106.
- Rochani AK, Balasubramanian S, Ravindran Girija A, Raveendran S, Borah A, Nagaoka Y, Nakajima Y, Maekawa T, Kumar DS. Dual mode of cancer cell destruction for pancreatic cancer therapy using Hsp90 inhibitor loaded polymeric nano magnetic formulation. Int J Pharm. 2016 Sep 10;511(1):648-58. Doi: 10.1016/j.ijpharm.2016.07.048. PubMed PMID: 27469073.