TumorHoPe: A Database of Tumor Homing Peptides Pallavi Kapoor, Harinder Singh, Ankur Gautam, Kumardeep Chaudhary, Rahul Kumar, Gajendra P. S. Raghava* Bioinformatics Centre, CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh, India Abstract Background: Cancer is responsible for millions of immature deaths every year and is an economical burden on developing countries. One of the major challenges in the present era is to design drugs that can specifically target tumor cells not normal cells. In this context, tumor homing peptides have drawn much attention. These peptides are playing a vital role in delivering drugs in tumor tissues with high specificity. In order to provide service to scientific community, we have developed a database of tumor homing peptides called TumorHoPe. Description: TumorHoPe is a manually curated database of experimentally validated tumor homing peptides that specifically recognize tumor cells and tumor associated microenvironment, i.e., angiogenesis. These peptides were collected and compiled from published papers, patents and databases. Current release of TumorHoPe contains 744 peptides. Each entry provides comprehensive information of a peptide that includes its sequence, target tumor, target cell, techniques of identification, peptide receptor, etc. In addition, we have derived various types of information from these peptide sequences that include secondary/tertiary structure, amino acid composition, and physicochemical properties of peptides. Peptides in this database have been found to target different types of tumors that include breast, lung, prostate, melanoma, colon, etc. These peptides have some common motifs including RGD (Arg-Gly-Asp) and NGR (Asn-Gly-Arg) motifs, which specifically recognize tumor angiogenic markers. TumorHoPe has been integrated with many web-based tools like simple/ complex search, database browsing and peptide mapping. These tools allow a user to search tumor homing peptides based on their amino acid composition, charge, polarity, hydrophobicity, etc. Conclusion: TumorHoPe is a unique database of its kind, which provides comprehensive information about experimentally validated tumor homing peptides and their target cells. This database will be very useful in designing peptide-based drugs and drug-delivery system. It is freely available at http://crdd.osdd.net/raghava/tumorhope/. Citation: Kapoor P, Singh H, Gautam A, Chaudhary K, Kumar R, et al. (2012) TumorHoPe: A Database of Tumor Homing Peptides. PLoS ONE 7(4): e35187. doi:10.1371/journal.pone.0035187 Editor: Bin Xue, University of South Florida, United States of America Received December 24, 2011; Accepted March 9, 2012; Published April 16, 2012 Copyright: 2012 Kapoor et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors are thankful to Council of Scientific and Industrial Research (CSIR), Open Source Drug Discovery (OSDD) and Department of Biotechnology, Government of India for providing research fellowships. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: raghava@imtech.res.in Introduction Cancer is one of the leading causes of immature deaths all over the world [1]. In 2008, more than 7 million deaths (around 13% of all deaths) occurred due to cancer and more new cancer cases are expected (http://www.scribd.com/doc/48974229/Global-Cancer- Statistics-2011) [2]. Both developed and developing countries are in the grip of this deadly disease. Despite tremendous progress in the field of cancer research, still we are unable to design effective and efficient anti-cancer therapy [3]. The current anti-cancer drugs are not selective and kill both tumor cells and normal cells. Therefore, designing drugs that specifically target cancer cells without affecting normal cells is one of the most challenging tasks for researchers. In order to overcome this limitation, various approaches/strategies/ delivery systems have been developed. These approaches include the use of engineered antibodies, cell penetrating peptides, tumor homing peptides, and aptamers [4]. In the last few years, tumor homing peptides have gained recognition as a drug delivery vehicle. Due to advancement in phage display technology, a large number of peptides have been discovered, which specifically bind to tumor cells. These peptides have a strong affinity towards a specific receptor/marker that is often present in many tumors and tumor vasculature. In several cases, some of these receptors/markers are over expressed in tumors, in comparison to their expression in normal tissues [5]. These peptides can also recognize angiogenic/metastatic lesions, which may not be detectable using other traditional methods [6]. Since these peptides home to tumor site/vasculature through the circulation, they are often called as tumor homing/ targeting peptide. Most of the tumor homing peptides have been identified by phage display technique [7] and have shown good accumu- lation at the tumor site, when injected in mice models [8]. Drugs conjugated to such peptides, when administered, have shown more efficacies in mice models [9], and many peptide based drugs are already in clinical trials [10,11]. In addition, these peptides have also been successfully used to deliver various imaging agent and inorganic nanoparticles [12]. Peptide based therapy has many advantages over the conventional anti-cancer chemotherapy. They are more specific and thus, exhibit lesser side effects [10]. In addition, due to direct delivery of the anti-cancer agent/drug to PLoS ONE | www.plosone.org 1 April 2012 | Volume 7 | Issue 4 | e35187