The Oncolytic Virus dl922-947 Triggers Immunogenic Cell Death in Mesothelioma and Reduces Xenograft Growth

Our plain-English summary of The Oncolytic Virus dl922-947 Triggers Immunogenic Cell Death in Mesothelioma and Reduces Xenograft Growth, by S. Di Somma, C.A. Iannuzzi, C. Passaro, et al (Frontiers in Oncology, 2019).

The study

• Authors: S. Di Somma, C.A. Iannuzzi, C. Passaro, I.M. Forte, R. Iannone, V. Gigantino, P. Indovina, G. Botti, A. Giordano, P. Formisano, G. Portella, A.M. Malfitano, F. Pentimalli
• Journal: Frontiers in Oncology
• Published: 2019;9:564
• Cited by: 48 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant pleural mesothelioma (MPM) is an aggressive cancer associated with asbestos exposure that urgently requires effective therapeutic strategies. Current treatments are unable to increase significantly patient survival, which is often limited to <1 year from diagnosis. Virotherapy, based on the use of oncolytic viruses that exert anti-cancer effects by direct cell lysis and through the induction of anti-tumor immune response, represents an alternative therapeutic option for rare tumors with limited life expectancy. In this study, we propose the use of the adenovirus dl922-947, engineered to allow selective replication in cancer cells, to counteract MPM. Methods: We performed a thorough preclinical assessment of dl922-947 effects in a set of MPM cell lines and xenografts. Cytotoxicity of dl922-947 alone and in combination assays was evaluated by sulforhodamine B assay. Cell cycle, calreticulin expression, and high mobility group box protein 1 (HMGB1) secretion were determined by flow cytometry, whereas ATP content was determined by a luminescence-based bioassay. The modulation of angiogenic factors in MPM-infected cells was evaluated through ELISA. Results: We found that dl922-947 infection exhibits cytotoxic effects in MPM cell lines, affecting cell viability, cell cycle progression, and regulating main hallmarks of immunogenic cell death inducing calreticulin surface exposure, HMGB1 and ATP release. Our results also suggest that dl922-947 may affect angiogenic signals by regulation of VEGF-A and IL-8 secretion. Furthermore, dl922-947 shows anti-tumor efficacy in murine xenograft models reducing tumor growth and enhancing survival. Finally, the combination with cisplatin potentiated the cytotoxic effect of dl922-947. Conclusions: Overall our data identify virotherapy, based on the use of dl922-947, as a new possible therapeutic strategy against MPM, which could be used alone, in combination with standard chemotherapy drugs, as shown here, or other approaches also aimed at enhancing the antitumoral immune response elicited by the virus.

In plain English

This was a laboratory study in human malignant pleural mesothelioma (MPM) cell lines and in mice, testing the oncolytic adenovirus dl922-947, which is engineered with a 24 bp deletion in the E1A conserved region 2 so that it replicates in cells with a defective retinoblastoma pathway. Asbestos exposure was background context, not an experimental variable: it was named as the main cause of mesothelioma and discussed in the authors' account of HMGB1 release and chronic inflammation. In sulforhodamine B viability assays, dl922-947 reduced viability with IC50 values of 5.3 p.f.u./cell (MSTO-211H), 4.3 (NCI-H28) and 103.6 (NCI-H2452), while NCI-H2052 viability was unaffected, which the authors linked to inefficient viral entry. Infection altered cell cycle profiles, increasing the subG1 and greater-than-4N populations, and modulated the three markers of immunogenic cell death (calreticulin surface exposure, HMGB1, reduced intracellular ATP). IL-8 fell significantly in MSTO-211H and VEGF-A in NCI-H28. In a pilot xenograft experiment (18 athymic mice, 9 per group), intra-tumoral dl922-947 reduced tumour growth and microvessel density, with complete regression in 3 animals. In the NCI-H28 and MSTO-211H cell-line assays only, cisplatin added 24 h after infection showed synergism (combination index below 1).

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Preclinical laboratory study: in vitro experiments in human mesothelioma cell lines plus a mouse xenograft experiment
• Who was studied: Four human MPM cell lines (NCI-H28, NCI-H2452, MSTO-211H, NCI-H2052) from ATCC, and 18 six-week-old female CD1 athymic mice bearing MSTO-211H xenografts, Naples, Italy
• Exposure: Infection with the oncolytic adenovirus dl922-947 (0.34 to 250 p.f.u./cell in vitro; 4 x 10^6 p.f.u. intra-tumorally twice weekly for 5 weeks in mice), alone and combined with cisplatin; comparators were wild-type adenovirus, non-replicating AdGFP and SAHA
• Main results:
  • Dose-dependent cytotoxicity in three cell lines, with IC50 values of 5.3, 4.3 and 103.6 p.f.u./cell for MSTO-211H, NCI-H28 and NCI-H2452; NCI-H2052 viability was not affected
  • In both MSTO-211H and NCI-H28, infection increased the subG1 phase and the greater-than-4N population
  • Calreticulin surface exposure increased and intracellular ATP decreased in both MSTO-211H and NCI-H28 after infection
  • Intracellular HMGB1 (with brefeldin A to block secretion) was increased in infected cells at 72 hpi
  • Pro-angiogenic factors: significant reduction of IL-8 in MSTO-211H and of VEGF-A in NCI-H28 at 48 hpi (p less than 0.05, Mann-Whitney test)
  • In the MSTO-211H xenograft model, tumour growth differed significantly between treated and control mice at day 28 (p less than 0.001)
  • Complete tumour regression occurred in 3 of the treated animals (reported as 30%), with no re-growth over 3 further months of observation
  • Immunohistochemistry of excised xenografts showed reduced tumour microvessel density (CD31) in treated versus control mice
  • In cell-line assays, cisplatin added 24 h after infection increased cytotoxicity in NCI-H28 and MSTO-211H, with combination index values below 1 indicating synergism
• The authors' conclusion: The authors concluded that dl922-947 induced immunogenic cell death and reduced angiogenic factor secretion in MPM cells, and could be a feasible strategy against mesothelioma, in combination with other agents
• Limitations the authors state:
  • The animal experiment was described by the authors as a pilot experiment
  • Three control animals were sacrificed early, so the difference in mean xenograft volume between groups may be understated
  • The virus was ineffective in the sarcomatoid-derived NCI-H2052 line because of inefficient viral entry, limiting applicability across MPM subtypes
  • The authors state the mechanisms by which dl922-947 induces cell death are only partially known
  • Some data referred to were not shown

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Pleural Mesothelioma, Asbestos Exposure, Life Expectancy, High Mobility Group Box 1 (HMGB1), Cisplatin, Chemotherapy.

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• Pharmacological inhibition of CDK4/6 impairs diffuse pleural mesothelioma 3D spheroid growth and reduces viability of cisplatin-resistant cells — A. Costa, I.M. Forte, et al. (2024)
• Systemic but not topical TRAIL-expressing mesenchymal stem cells reduce tumour growth in malignant mesothelioma — E.K. Sage, K.K. Kolluri, et al. (2014)
• A₃ receptors are overexpressed in pleura from patients with mesothelioma and reduce cell growth via Akt/nuclear factor-κB pathway — K. Varani, S. Maniero, et al. (2011)
• A Redox-Inactive Derivative of Tocotrienol Suppresses Tumor Growth of Mesothelioma Cells in a Xenograft Model — A. Sato, T. Arai, et al. (2019)
• Complete regression of human malignant mesothelioma xenografts following local injection of midkine promoter-driven oncolytic adenovirus — S. Kubo, Y. Kawasaki, et al. (2010)

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