June 7, 2015

PV-10: Total cell death, changes in nitric oxide production and intracellular pH, within hours of exposure. Step 5?

At first blush the University of Illinois at Chicago's College of Medicine's Department of Surgical Oncology's Ajay Maker Laboratory's PV-10 (rose bengal)-related abstract of their preclinical colorectal cancer murine model work (see abstract P134, page S86) at the 2015 annual meeting of the Society of Surgical Oncology ("SSO") — see my blog post Intralesional Injection of Rose Bengal Induces an Anti-tumor Immune Response and Potent Tumor Regressions in a Murine Model of Colon Cancer — led me to frame a narrative of:
  • Multiple third party medical research institutions (Florida's Moffitt Cancer Center, Illinois' University of Illinois at Chicago or UIC) at arms length from Provectus, having received only PV-10 from Provectus but operating under unrestricted grants from the company,
  • Demonstrated (preclinically) both prongs of PV-10's approach to fighting cancer: (a) a local effect generated via tumor ablation following injection, and (b) a systemic effect delivered via a subsequent tumor-specific immune response,
Click to enlarge. A screenshot from Provectus' investor presentation
  • In multiple indications (melanoma, breast cancer, colorectal cancer). See the blog's News page item Third party non-clinical work (June 5, 2015).
Stepping back, as a result of re-reading the UIC abstract, I was struck by the Results statement:
"PV-10 induced near total cell death, corresponding increases in nitric oxide production, and decreased intracellular pH in both CT26 murine and HT29 human CRC cells within hours of exposure compared to controls (p<0.01), and at levels similar to 5FU." {Underlined emphasis is mine}
Note: 5FU is another name for fluorouracil, a systemic chemotherapy given for "...anal, breast, colorectal, oesophageal, stomach, pancreatic and skin cancers (especially head and neck cancers)."

Rose Bengal ("RB") is the active pharmaceutical ingredient in Provectus' investigational oncology compound PV-10 (a 10% solution of RB) as well as the company's investigational dermatology compound PH-10 (a 0.001% to 0.01% gel of RB).

Cell death by RB [without affecting normal material] is well cited in biomedical literature by Provectus as well as folks outside of company founders/innovators, such as (reverse chronological order):
  1. 2015: O2 and ca(2+) fluxes as indicators of apoptosis induced by rose bengal-mediated photodynamic therapy in human oral squamous carcinoma cells,
  2. 2015: UIC above,
  3. 2014: Rose Bengal suppresses gastric cancer cell proliferation via apoptosis and inhibits nitric oxide formation in macrophages,
  4. 2012: Selective toxicity of rose bengal to ovarian cancer cells in vitro,
  5. 2012 to date: Moffitt,
  6. 2009: Enzyme-assisted photosensitization activates different apoptotic pathways in Rose Bengal acetate treated HeLa cells. Histochemistry and Cell Biology, and
  7. 2006: Rose bengal induces dual modes of cell death in melanoma cells and has clinical activity against melanoma
Changes in nitric oxide production because of RB is much less documented or discussed. Nitric oxide, or chemical name NO:
"...is said to have both tumoricidal as well as tumor promoting effects which depend on its timing, location, and concentration. NO has been suggested to modulate different cancer-related events including angiogenesis, apoptosis, cell cycle, invasion, and metastasis. On the other hand, it is also emerging as a potential anti-oncogenic agent." (2013: Nitric oxide and cancer: a review) {Underlined emphasis is mine}
"Paradoxically therefore, NO (and related reactive nitrogen species) may have both genotoxic and angiogenic properties."
UIC discuss increased NO production induced by PV-10 (RB).

Rabe et al. discuss the inhibition of NO formation in macrophages induced by RB. Macrophages are a type of white blood cell:
"The tumor microenvironment is a complex ecology of cells that evolves with and provides support to tumor cells during the transition to malignancy. Among the innate and adaptive immune cells recruited to the tumor site, macrophages are particularly abundant and are present at all stages of tumor progression. Clinical studies and experimental mouse models indicate that these macrophages generally play a protumoral role. In the primary tumor, macrophages can stimulate angiogenesis and enhance tumor cell invasion, motility, and intravasation. During monocytes and/or metastasis, macrophages prime the premetastatic site and promote tumor cell extravasation, survival, and persistent growth. Macrophages are also immunosuppressive, preventing tumor cell attack by natural killer and T cells during tumor progression and after recovery from chemo- or immunotherapy. Therapeutic success in targeting these protumoral roles in preclinical models and in early clinical trials suggests that macrophages are attractive targets as part of combination therapy in cancer treatment." (2014: Tumor-Associated Macrophages: From Mechanisms to Therapy) {Underlined emphasis is mine}
Through medical literature to date, PV-10 could be associated with several steps of Chen and Mellman's cancer-immunity cycle.
Click to enlarge. Full presentation is here.
Of the remaining steps to be associated with/linked to PV-10 is Step 5, where inhibitors of vascular endothelial growth factor ("VEGF") potentially can promote T cell infiltration into tumors (paraphrased from Chen & Mellman's paper). Nitric oxide, VEGF and angiogenesis are linked; "[a]ngiogenesis is a normal and vital process in growth and development, as well as in wound healing and in the formation of granulation tissue. However, it is also a fundamental step in the transition of tumors from a benign state to a malignant one..." Anti-angiogenesis treatment presumably prevents tumors from having their own blood supply, and thus grow.

It was rumored the UIC work was kicked-off around ASCO 2014. Moffitt presented additional pre-clinical and clinical work related to their mechanism of action study of PV-10 at AACR and ASCO 2014. It also was rumored an undetermined time ago Moffitt had associated/linked PV-10 with/to every step of the cancer-immunity cycle but one.

Does the UIC work confirm Moffitt's work on Step 5, or does it fill-in their work? Perhaps the more pertinent question is whether or not PV-10 may be associated with/linked to all steps of the cancer-immunity cycle.

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