N.B. There is no reference to Rose Bengal (generic name) or PV-10 (proprietary name) in the February 2015 Garg et al. article.
Article Abstract: Phagocytosis of dying cells is a major homeostatic process that represents the final stage of cell death in a tissue context. Under basal conditions, in a diseased tissue (such as cancer) or after treatment with cytotoxic therapies (such as anticancer therapies), phagocytosis has a major role in avoiding toxic accumulation of cellular corpses. Recognition and phagocytosis of dying cancer cells dictate the eventual immunological consequences (i.e., tolerogenic, inflammatory or immunogenic) depending on a series of factors, including the type of ‘eat me’ signals. Homeostatic clearance of dying cancer cells (i.e., tolerogenic phagocytosis) tends to facilitate pro-tumorigenic processes and actively suppress antitumour immunity. Conversely, cancer cells killed by immunogenic anticancer therapies may stimulate non-homeostatic clearance by antigen-presenting cells and drive cancer antigen-directed immunity. On the other hand, (a general) inflammatory clearance of dying cancer cells could have pro-tumorigenic or antitumorigenic consequences depending on the context. Interestingly, the immunosuppressive consequences that accompany tolerogenic phagocytosis can be reversed through immune-checkpoint therapies. In the present review, we discuss the pivotal role of phagocytosis in regulating responses to anticancer therapy. We give particular attention to the role of phagocytosis following treatment with immunogenic or immune-checkpoint therapies, the clinical prognostic and predictive significance of phagocytic signals for cancer patients and the therapeutic strategies that can be employed for direct targeting of phagocytic determinants.Provectus says PV-10/Rose Bengal:
- Does not rely on a single pathway to work [I assume 'signalling pathway'],
- Does not focus on a single receptor to work [I assume 'cell receptor'], and
- Has no known resistance [I assume little no cancer drug resistance].
A highly specific compound in its targeting of only diseased (cancerous) tumors/lesions, tissue and cells, sparing healthy ones in the process, might the veracity of PV-10/Rose Bengal's "multiplicity" be based in its lack of "specificity" in regards to cell death?
That is, might Provectus' investigational compound's apparent implication in different kinds of cell death help explain why PV-10/Rose Bengal does not rely on a single pathway or focus on a single receptor to work, and has no known resistance?
Of note in Garg et al.'s article are (a) a table describing "major cell death pathways and their immunobiological" profiles and (b) a figure illustrating "therapeutic exploitation of phagocytosis of dying cancer cells for T-cell-mediated cancer cell elimination."
The table of major cell death pathways includes (i) apoptosis, (ii) autophagy (autophagic cell death) and (iii) immunogenic cell death.
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The illustration appears to draw three paths to anti-tumor immunity; one that is direct (e.g., DAMPs like HMGB1), and two that additionally employ co-stimulatory signals such as TLR agonists or co-inhibitory signals such as immune checkpoint therapy.
|Click to enlarge. Image source|
A sampling of Provectus and independent medical researcher work implicates PV-10 in apoptosis, autophagy, necrosis, and immunogenic cell death:
- Provectus: "The patient who had chemotherapy radioresistant recurrent disease in the head and neck area had rapid necrosis of the injected metastasis and this as well as 3 uninjected sc metastases underwent complete remission over a period of several months," "Rose Bengal induces dual modes of cell death in melanoma cells and has clinical activity against melanoma," Melanoma Research 16(Suppl 1):S8, Sep 2006
- Provectus: "PV-10 accumulation elicits acute autophagy of cancer cells," "Chemoablation of Metastatic Melanoma with PV-10," Presentation at 4th Interdisciplinary Melanoma & Skin Cancer Centres Meeting, Sydney, AU, Nov 2010
- University of Illinois at Chicago: "Treatment of colon cancer cells with PV-10 induced cell cycle arrest, apoptosis, autophagy, and significant ER stress; consistent with immunogenic apoptosis," "PV-10 Induces Potent Immunogenic Apoptosis in Colon Cancer Cells," ASC 2016
- Quote by Provectus about Moffitt Cancer Center work: "This paper is a watershed event in the development of PV-10, walking the reader through all the steps of immune activation after PV-10 injection, from immunogenic cell death and signaling via release of HMGB1, dendritic cell recruitment and infiltration into draining lymph nodes, activation of tumor-specific T cells, and killing of uninjected tumors upon infiltration by these T cells." "Intralesional Rose Bengal in Melanoma Elicits Tumor Immunity Via Activation of Dendritic Cells by the Release of High Mobility Group Box 1," Oncotarget 2016.
Some cell death via PV-10 occurs in the injected lesion or tumor (i.e., tumor-resident), which is the upstream trigger of subsequent cell death via a tumor-specific immune response (i.e., therapy-recruited).