In Vivo Detection of Human TRPV6-Rich Tumors with Anti-Cancer Peptides Derived from Soricidin. Chris V. Bowen1, Drew DeBay1, H. Stephen Ewart2., Pamela Gallant2, Sean Gormley3, T. Toney Ilenchuk3, Umar Iqbal4, Tyler Lutes3, Marzia Martina4, Geoffrey Mealing4, Nadine Merkley2, Sandra Sperker2, Maria J. Moreno4, Christopher Rice3, Raymond T. Syvitski2, John M. Stewart3* PLoS ONE 8(3): e58866. doi:10.1371/journal.pone.0058866
1. National Research Council of Canada, Institute for Biodiagnostics (Atlantic) - Neuroimaging Research Laboratory, Halifax, Nova Scotia, Canada,
2. National Research Council of Canada, Institute for Marine Biosciences, Halifax, Nova Scotia, Canada,
3. Soricimed Biopharma Inc., Sackville, New Brunswick, Canada,
4. National Research Council of Canada, Institute of Biological Sciences - Neurobiology Program, Ottawa, Ontario, Canada
Soricidin is a 54-amino acid peptide found in the paralytic venom of the northern short-tailed shrew (Blarina brevicauda) and has been found to inhibit the transient receptor potential of vallinoid type 6 (TRPV6) calcium channels. We report that two shorter peptides, SOR-C13 and SOR-C27, derived from the C-terminus of soricidin, are high-affinity antagonists of human TRPV6 channels that are up-regulated in a number of cancers. Herein, we report molecular imaging methods that demonstrate the in vivo diagnostic potential of SOR-C13 and SOR-C27 to target tumor sites in mice bearing ovarian or prostate tumors. Our results suggest that these novel peptides may provide an avenue to deliver diagnostic and therapeutic reagents directly to TRPV6-rich tumors and, as such, have potential applications for a range of carcinomas including ovarian, breast, thyroid, prostate and colon, as well as certain leukemia’s and lymphomas.
Full article here.
Scientific Conference Presentations
Bio-Accumulation of a TRPV6 Binding Peptide SOR-C27 in an Ovarian Cancer Mouse Model by Magnetic Resonance Imaging. Beatrice Hunter Cancer Conference, Halifax, 8 Nov., 2011. Drew DeBay, Chris Bowen, Stephen Ewart, Nadine Merkely, Ray Syvitski and Jack Stewart.
Abstract: From previous investigations, a fragment of a paralytic peptide from the Northern Short Tail shrew SOR-C27 was found to bind to the calcium ion channel TRPV6, which is highly over-expressed by breast, prostate and ovarian cancers. The fragment peptide was structurally characterized and the bio-accumulation assessed within a SKOV-3 ovarian tumour xenograft mouse model as proof-of-concept for this peptide technology. US Patent #US2010/0329983 A1
Click here to view the poster board from this presentation.
Advances in TRPV6-based diagnostics in cancer. 9th Annual Ion Channel Retreat, Vancouver, BC, June 2011. Presented by J. M. Stewart, CSO, Soricimed Biopharma Inc.
Abstract: In previous presentations before this workshop and elsewhere we have shown the application of a novel peptide platform derived from soricidin* to treatment of human tumours in animal models through the antagonist action on TRPV6. One of our peptides is expected to enter Phase I cancer trials during 2011. Also, we provided early indications that there may be diagnostic applications of the peptides and of over-production of TRPV6 channels in breast, ovarian and prostate cancers to augment traditional antibody and nucleotide-based assessment of biopsies.
Now we describe the recent application of our TRPV6-binding peptides (the SOR-C-series) to detect and measure TRPV6-rich ovarian and prostate tumors with imaging technologies (fluorescent and MRI highlighted here). The fluorescent tagging of tumors in a mouse model is rapid, showing a maximal signal at about 3 hrs and long lasting (at least 72 hours). As a negative enhancer for MRI, nanoparticles of SPIO (superparamagnetic iron oxide) bearing a C-series peptide avidly binds to xenografted human ovarian tumors in a mouse model allowing both location and measurement of tumor volume.
Because of over-expression of TRPV6 in epithelial cancers and because cancer cells shed various microvesicular structures, we hypothesized that the TRPV6 signature of these cancers would be carried by body fluids. We provide evidence to support this hypothesis and show it is possible to detect earliest stage cancers (Stage I and II) from a blood sample using a nucleotide-based measurement of cell-free, microvesicular TRPV6 mRNA. The amount of circulating TRPV6 mRNA from cancer patients is significantly greater than found in healthy people and represents an easily accessible way to monitor this biomarker. This over-abundance of TRPV6 mRNA in body fluids may provide an avenue to an early diagnostic.
*Soricidin is the paralytic peptide present in the saliva of the Northern Short-tailed shrew.
Conference Report: Saranna Brugger, Marco Garate, Gina Papaianni, Maria Volnoukhin, Chris Zhan, Sikander Gill, Sophia Liang, and Dong Liang, The Ninth Annual Ion Channel Retreat, Vancouver, Canada, June 27–29, 2011. ASSAY and Drug Development Technologies, 9(6): 1-9.
The conference report can be read here.
A novel anti-cancer agent works through a targeted physiological mechanism involving the non-voltage gated calcium channel, TRPV6. 7th Annual Ion Channel Retreat, Vancouver, Canada, June 29 – July 1, 2009. Presented by J. M. Stewart, CSO, Soricimed Biopharma Inc.
Abstract: About 10 years ago it was noted that cancers arising from epithelia of prostate, breast and ovaries expressed large quantities of a non-voltage gated calcium channel now called TRPV6 (Transient Receptor Potential Vanilloid family, number 6). As well, it was noted that the severity of malignancies seemed to correlate with the level of TRPV6 expression, with healthy tissue expressing either no or very low levels of this channel. During the last decade we have learned of the involvement of this calcium channel in cancer and how it appears to trigger a pro-survival pathway mediated by the NFAT transduction factor. Also during the last decade it has been pointed out, repeatedly, that this ion channel could be a target for therapeutic intervention in cancers of these tissues. Until now, only poor antagonists to TRPV6 have been reported.
In the course of investigating the paralytic component of the saliva of a shrew common to Eastern North America, the Northern short-tailed shrew (Blarina brevicauda) we isolated a medium-sized peptide that is biologically bifunctional. It causes paralysis through inhibition of sodium channels and also severely inhibits calcium currents through TRPV6. It was the latter property that we were able to dissect from the parent peptide and use to test the hypothesis that TRPV6 was integral in these epithelial cancers. We report here the discovery of two small peptides, their efficacy in inhibiting TRPV6 (IC50 ~ 100 to 150 nM) and their ability to initiate a shut down of the pro-survival pathway present in breast, ovarian and prostate cancers resulting from the increased TRPV6-mediated calcium influx. The upshot of the specific inhibition of TRPV6 is induction of a cytological state, rather than a cytotoxic one (typical of small molecule therapy), resetting the cell and inducing apoptosis. Healthy cells, not having increased levels of TRPV6 are not significantly affected by the peptide treatment. The new peptides represent a novel anti-cancer agent working through a targeted physiological mechanism. [Note: subsequent work indicates the IC50 values range between 10 nM and 50 nM.]
A novel peptide inhibitor of TRPV6 shows activity against ovarian cancer in vitro and in vivo. 1st International Congress on TRP Channels, Karolinska Institute, Stockholm, Sweden, 2009. TRP Channels from Sensory Signaling to Human Disease, J. M. Stewart, T. T. Ilenchuk, J. A. Blakely, T. W. D. Lutes, C. T. Rice, and K. D. M. Harris. Presented by J. M. Stewart, CSO, Soricimed Biopharma Inc.
Abstract: We report the first significant inhibitor of TRPV6 derived from a fragment of the paralytic salivary peptide produced by the Northern Short-tailed shrew, Blarina brevicauda. In the course of investigating the paralytic component of the saliva of a shrew common to Eastern North America we isolated a medium-sized polypeptide (54 aa) responsible for the paralysis. We report here the discovery of two smaller derivative peptides, their efficacy in inhibiting TRPV6 (IC50 ~ 100 to 150 nM), their ability to initiate erasure of the pro-survival pathway present in ovarian cancer that results from the increased TRPV6-mediated calcium influx and their ability to induce apoptosis. Healthy cells, not having increased levels of TRPV6 are unaffected by the peptide treatment as corroborated by the non-toxic nature of the peptides. Further we exploit the specific binding to TRPV6 by attaching fluorescent marker to the peptide: we can detect TRPV6-rich cells. The new peptides represent a novel anti-cancer agent working through a targeted physiological mechanism. [Note: subsequent work indicates the IC50 values range between 10 nM and 50 nM.]
T. T. Ilenchuk Virtual Outsourcing: A Case Study. Presented at the ‘Outsourcing in Clinical Trials Canada. Toronto, ON. 25-26 October, 2011
To read Toney's presentation click here.
General Presentations & Lectures
J. M. Stewart, Curiosity to Clinical Trials. Presented to the 3rd Annual Conference of the New Brunswick Health Research Foundation meeting 8-9 Nov., 2011, Moncton, NB.
J. M. Stewart, From Curiosity to Clinical Trials v2.0. Presentation to general audience, sponsored by the Heath Outreach group of Mount Allison University. Sackville, NB, 2 Nov., 2011.
J. M. Stewart, From Curiosity to Clinical Trials, Lecture presented to senior research students, Mount Allison University, May, 2011.
J.M. Stewart, Over-expression of the calcium ion channel TRPV6 is the focus for a targeted management of ovarian cancer: early detection and treatment. Invited presentation to ‘Maritech 2010’, Moncton, June, 2010 (annual conference of Medical Laboratory Technologists). Moncton, NB, Canada.
J.M. Stewart and K. Keirstead. From the Academy to the Street: Barriers to Overcome. Commercialization workshop organized by BioAtlantech, March, 2010, Fredericton, NB, Canada
J. M. Stewart, The discovery of a novel anti-cancer agent that works through a physiological mechanism targeted at the non-voltage gated calcium channel, TRPV6. Keynote speaker, Memorial University, Graduate Student Conference, Faculty of Medicine, 6 June, 2009. St. John’s, NFLD, Canada.
JM Stewart A Novel anti-cancer agent works through the calcium channel, TRPV6. Lecture presented to BC Cancer Agency staff, 3 July, 2009, Paetzold Health Education Centre, Vancouver General Hospital, Vancouver, BC, Canada