SITC 2016, ABSTRACT: Intralesional injection with Rose Bengal and systemic chemotherapy induces anti-tumor immunity in a murine model of pancreatic cancer

Updated below: 11/8/16 {thrice}.

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Intralesional injection with Rose Bengal and systemic chemotherapy induces anti-tumor immunity in a murine model of pancreatic cancer

Shari Pilon-Thomas, Amy Weber, Jennifer Morse, Krithika Kodumudi, Hao Liu, John Mullinax, Amod A Sarnaik H. Lee Moffitt Cancer Center, Tampa, FL, USA

Journal for ImmunoTherapy of Cancer 2016, 4(Suppl 1):P256

Background
Rose Bengal is a xanthene dye that has been utilized for liver function studies and is currently used topically in ophthalmology. Intralesional (IL) Rose Bengal (PV-10) has been shown in murine models and melanoma clinical trials to induce regression of treated melanoma lesions and uninjected bystander lesions. This study was undertaken to measure whether IL PV-10 can induce systemic anti-tumor effects alone or in combination with gemcitabine (Gem) therapy in a murine model of pancreatic cancer.

Methods
C57BL/6 mice received Panc02 pancreatic tumor cells subcutaneously (SC) on one flank to establish a single tumor. On day 7, tumor was treated with IL PV-10. Control mice received IL phosphate
buffered saline (PBS). Tumor growth was measured. Splenic T cells were collected and co-cultured with Panc02 or irrelevant B16 cells. Supernatants were collected to measure Panc02-specific T cell responses by IFN-gamma ELISA. To measure the effect of IL PV-10 on the growth of an untreated, bystander tumor, mice received Panc02 cells in bilateral flanks. The resulting right tumor was injected IL with PV-10 or PBS. Tumor sizes were measured for both the right (treated) and left (untreated/bystander) tumors. To determine the efficacy of combination therapy with IL PV-10 and systemic Gem, mice bearing a single or bilateral Panc02 tumors were treated with PV-10 alone or in combination with Gem. Mice received 60 mg/kg Gem intraperitoneally (IP) twice per week.

Results
C57BL/6 mice bearing Panc02 tumors treated with IL PV-10 had significantly smaller tumors than mice treated with PBS (p < 0.001). A significant increase in the IFN-gamma production in response to Panc02 was measured in the splenocytes of mice treated with PV-10 as compared to mice treated with PBS (p < 0.05). Mice with bilateral tumors had a significant regression of tumors injected IL with PV- 10 and there was a reduction in the untreated (bystander) flank Panc02 tumor (p < 0.01). Gem therapy in combination with IL PV-10 injection led to enhanced tumor regression (p < 0.05) compared to IL PV-10 or Gem alone in both a single tumor model and a bilateral tumor model.

Conclusions
Regression of untreated pancreatic tumors by IL injection of PV-10 in concomitant tumor supports the induction of a systemic anti-tumor response. Addition of Gem chemotherapy enhances the effects of IL PV-10 therapy. Given that patients with metastatic pancreatic cancer have a dismal prognosis, combination therapy of IL PV-10 combined with Gem may benefit patients with metastatic pancreatic cancer.

Updated (11/8/16).1: My underlined emphasis above. Note PV-10 use in the above murine model work as a monotherapy, and in combination with systemic chemotherapy.

Updated (11/8/16).2: H/t @bradpalm1:

Click to enlarge. Tweet image source

"Gemcitabine reduces MDSCs, tregs and TGFβ-1 while restoring the teff/treg ratio in patients with pancreatic cancer," Eriksson et al., Journal of Translational Medicine 2016 14:282

"Conclusions 

Gemcitabine regulates the immune system in patients with pancreatic cancer including MDSCs, Tregs and molecules such as TGFβ-1 but does not hamper the ability of effector lymphocytes to expand to stimuli. Hence, it may be of high interest to use gemcitabine as a conditioning strategy together with immunotherapy."

Updated (11/8/16).3: Unlike some, I do not read too much into Moffitt's abstract with respect to the additivity or synergism of PV-10 and gemcitabine (systemic chemotherapy) based on the cancer center's murine model work (i.e., p values of PV-10 alone, and in combination with chemo). And, I'd like to see the poster if Provectus facilitates its release (e.g., the company did not facilitate the release of Moffitt's AACR 2016 poster, which I believe may lead to a peer-reviewed publication).

I believe the point of this mousie work, which of course is beyond cell line (in vitro) work but behind clinical studies, is to demonstrate in principle that (a) intralesional (IL) PV-10 could be used to treat pancreatic cancer (i.e., tumor type, leading to a suitable cancer indication) via (i) ablation/destruction of an injected tumor and (ii) the subsequent triggering of the immune response to reduce or destroy an untreated one, and (b) IL PV-10 plus chemo sees enhanced untreated tumor reduction or destruction.

These principles of (x) ablation/destruction by injection and (y) immunologic signalling (immune system harnessing) already have been shown preclinically by Moffitt for PV-10 as a monotherapy in melanoma (also clinically) and breast cancer (AACR 2013), and in combination with checkpoint inhibition for melanoma (SITC 2014).

So, this continues Rose Bengal, PV-10 and Provectus' theme of (A) agnosticism (ablation, immunologic signalling), (B) synergism (in that one therapy enhances another; "induce and boost"), (C) orthogonality (although this would be better shown in clinical work to emphasize no greater toxicity, if not less to far less), and...

(D) PV-10 is an immunotherapy. See January 19, 2016 blog post PV-10 is an immunotherapy.