Could PV-10 (Rose Bengal) be implicated in different kinds of cell death?

Image source

Reference article: Garg et al., Immunogenic versus tolerogenic phagocytosis during anticancer therapy: mechanisms and clinical translation, Cell Death and Differentiation (2016) 23, 938–951.

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.

Click to enlarge. Image source

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.

Garg et al. observe "The mechanisms of cancer cell death elicited by anticancer therapy and the type of phagocytes (e.g., tumour-resident versus therapy-recruited) interacting with dying cells are decisive factors in making a difference between anti-inflammatory or pro-inflammatory responses."

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).

$PVCT: Florey, Chain & Heatley

Chemoablation via PV-10 Ablation Causes Antigenization

& Antigenization Causes Immunization

[I encourage you to click on the hyperlinks for certain words and phrases to attain more information on them.]

PV-10 causes antigenization. Antigenization causes immunization.

Antigenization is the expression of antigens, in a tumor into which PV-10 has been injected, in context. Immunization is "the process by which...[the] immune system becomes fortified against an agent."

PV-10 facilitates the relationship between antigenization and immunization.

Ablation: "In medicine, ablation is the same as removal of a part of biological tissue..." "Biological ablation is the removal of a biological structure or functionality."

Chemoblation: A process whereby cells undergo a form of cell death that mimics features of both necrosis and apoptosis.

PV-10 is an immuno-chemoablative agent.

The process of immunization (immuno-) is unlocked by PV-10 chemoablation (-chemoablative), which causes the rapid, durable necrosis of the tumor lesions.

PV-10 is both a metabolic agent (a chemoablative, and in the same general class as inhibitors) and also
an immunotherapeutic agent (in the same general class as immunomodulatory agents like ipilimumab, tremelimumab, PD-1, PD-L1, etc.).

PV-10 elicits cell destruction naturally; that is, apoptosis-like, which Provectus refers to as autolysis.

Unlike like necrosis, "which is a form of traumatic cell death that results from acute cellular injury," apoptosis "is the process of programmed cell death." Autolysis, "more commonly known as self-digestion, refers to the destruction of a cell through the action of its own enzymes."

The key to PV-10 is diseased (cancerous) tissue cells are destroyed the way the body intended to destroy deficient or unnatural cells in the first place. PV-10 neither denature these cells nor changes their DNA.

The activity PV-10 induces in diseased cells causes antigenization, or the showering of antigens, whereby many, many, many antigens are shown to antigen presenting cells ("APCs"). These APCs then can choose which of the antigens to show (present) to the body's T cells, natural killer T ("NKT") cells, Tumor-infiltrating lymphocytes ("TILs"), etc.

This work is done, thus, in situ, or in the tumor. Provectus and Moffitt Cancer Center have demonstrated PV-10 induces tumor-specific T cell-mediated immunity, and referred to the application of PV-10 as an in situ vaccination. PV-10 itself is the vaccine, or vaccination.

• Society of Surgical Oncology (March, 2012)
• European Society for Medical Oncology (September/October 2012)
• Society for Immunotherapy of Cancer (October 2012) 
• American Association for Cancer Research (April 2013): Moffitt and Provectus

Induction: Bring about, initiating, increasing.

Immunity: "The state of having sufficient biological defences to avoid infection, disease, or other unwanted biological invasion."

Vaccination: "The administration of antigenic material (a vaccine) to stimulate an individual's immune system to develop adaptive immunity to a pathogen.

Is PV-10, itself, the "Holy Grail?"

Fareed Zakaria, in a December 10, 2012 interview on Fareed Zakaria GPS of Dr. Ronald DePinho, M.D., President of MD Anderson's cancer center, said "The holy grail for cancer would be to trigger the body’s own immune system to fight off the cancer, so that you somehow stimulate the antibodies in a way that that happens." The treatment that is the holy grail for cancer is not the grail itself. Rather, the grail is what the treatment inspires, produces, engenders, induces, etc.: a strong, durable, portable immune-mediated response.

Does PV-10 immunize the treated patient against his or her cancer?

Immunization: The process by which an individual's immune system becomes fortified against an agent.

Is PV-10 an immunization for cancer? Is PV-10 the "penicillin for cancer?" Rose Bengal, a compound around for so long and so simple in structure and application to its intended medical end use. PV-10, a miracle or wonder drug like penicillin?

Only time can and will tell.

Peter is fond of saying the discovery process of PV-10 is akin to peeling back or away the layers of the onion. It appears to me the core of this onion is the actuality of PV-10 as an immunization for cancer. In this moment in time, the world is peeling away the layers in the direction of this, but it still is some distance from it.

"The development of penicillin for use as a medicine is attributed to the Australian Nobel laureate Howard Walter Florey, together with the German Nobel laureate Ernst Chain and the English biochemist Norman Heatley."

The discovery of penicillin: "That Alexander Fleming discovered penicillin by chance is a myth. Before Fleming, there were a series of observations that influenced his research, and allowed him to come to the correct conclusion when a chance contamination in his bacterial culture was observed. This same opportunity came to others as well, but their only response to the contamination was that it had ruined their experiment and they had discarded the cultures and thought nothing more of it.

Discoveries in science are rarely made by chance. Often, it involves knowledge that has been gained over a long period of time so that all discoveries, today, have come about because we have "stood on the shoulders of giants that have come before us.""

Selective toxicity of rose bengal to ovarian cancer cells in vitro

Paper here. Published June 30, 2012.

Author: Steven B. Koevary, Department of Biomedical Sciences and Disease, New England College of Optometry & Department of Cell Biology, University of Massachusetts Medical School

Abstract: Rose bengal (RB) has been utilized as a photodynamic agent for the targeted killing of cancer cells. Recent data suggest that intralesional RB alone may be effective in chemoablating locoregional and metastatic melanomas. The ability of RB to induce direct and bystander melanoma cell death led to the speculation that it may be similarly effective in the treatment of other neoplasms. The objective of this study was to determine whether RB can limit the growth, or kill, ovarian cancer cells in vitro. Ovarian carcinoma cells with or without a germline BRCA1 mutation were cultured with up to 800 µM RB for one hour or four days, after which their ability to proliferate was assessed using the MTT assay. Control cells included an embryonic kidney cell line transformed with adenovirus, and normal human fibroblasts. Ovarian cancer cells exhibited significant dose-dependent suppression of growth in response to RB; this suppression was similar to that seen with carboplatin. RB treated ovarian cancer cells appeared rounded, shrunken, and damaged. RB also inhibited the growth of kidney tumor cells but was much less effective in slowing the growth of normal human fibroblasts suggesting that RB-mediated growth suppression might be tumor cell specific. Ovarian cancer cells treated with RB displayed a significant increase in apoptosis that peaked at approximately four times the levels seen in untreated control cells. Furthermore, RB exposure resulted in the intracellular generation of reactive oxygen species (ROS) at levels that were significantly greater than in untreated cells and similar to levels seen in cells treated short term with H2O2. These data suggest that RB may not only suppress ovarian cancer cell growth but also induce their apoptotic cell death, justifying the further investigation of the effects of RB in an animal model of ovarian cancer.  

"Thus, even when optimally debulked, many patients still exhibit tumor nodules too small to have been resected by even the most skilled surgeon that likely seed future growths. In light of the above data, it is theorized that injection of these nodules with RB at the time of surgery may prove to be an effective strategy for not only their elimination, but for vaccinating patients against the future regrowth of gross tumors. This notion is supported by data that showed that PV-10 treatment increased the levels of tumor infiltrating lymphocytes and that the overall survival of ovarian cancer patients was greater in patients whose tumors contained T cells."