Gillian Murphy, Ph.D.
Professor, Department of Oncology, University of Cambridge, UK
A novel strategy for targeting metalloproteinases in cancer
Epithelial tumours evolve in a multi-step manner, involving both inflammatory and mesenchymal cells. Although intrinsic factors drive malignant progression, the influence of the micro-environment of neoplastic cells is a major feature of tumorigenesis. Extracellular proteinases, notably the metalloproteinases, are key players in the regulation of this cellular environment, acting as major effectors of both cell-cell and cell-extracellular matrix (ECM) interactions. They are involved in modifying ECM integrity, growth factor availability and the function of cell surface signalling systems, with consequent effects on cellular differentiation, proliferation and apoptosis.This has made metalloproteinases important targets for therapeutic interventions in cancer and small molecule inhibitors focussed on chelation of the active site zinc and binding within the immediate active site pocket were developed. These were not successful in early clinical trials due to the relative lack of specificity and precise knowledge of the target proteinase(s) in specific cancers. We can now appreciate that it is essential that we understand the relative roles of the different enzymes (of which there are over 60) in terms of their pro and anti tumour activity and their precise sites of expression The next generations of metalloproteinase inhibitors need the added specificity that might be gained from an understanding of the structure of individual active sites and the role of extra catalytic domains in substrate binding and other aspects of their biology. We have prepared scFv antibodies to the extra catalytic domains of two membrane metalloproteinases, MMP-14 and ADAM17, that play key roles in the tumour microenvironment. Our rationale and experiences with these agents will be presented in more detail.
Shigeki Miyamoto, Ph.D.
Professor, McArdle Laboratory for Cancer Research – UW Carbone Cancer Center
Department of Oncology, School of Medicine and Public Health
University of Wisconsin-Madison
“Inside-out” NF-κB signaling in cancer and other pathologies
The NF-κB/Rel family of transcription factors contributes to critical cellular processes, including immune, inflammatory and cell survival responses. As such, NF-κB is implicated in immunity-related diseases, as well as multiple types of human malignancies. Indeed, genetic alterations in the NF-κB signaling pathway are frequently observed in multiple human malignancies. NF-κB is normally kept inactive in the cytoplasm by inhibitor proteins. Extracellular ligands can induce the release of NF-κB from the inhibitors to allow its migration into the nucleus to regulate a variety of target genes. NF-κB activation is also induced in response to multiple stress conditions, including those induced by DNA-damaging anticancer agents. Although precise mechanisms are still unclear, research from our group has revealed a unique nuclear-to-cytoplasmic signaling pathway. In collaboration with bioengineers, clinicians and pharmaceutical industry, our lab has developed new methods to analyze primary cancer patient samples and identified several compounds with different mechanisms that mitigate this cell survival pathway. Further contributions from other labs have also revealed additional mechanisms and molecular players in this “inside-out” signaling pathway and expanded its role in other physiological and pathological processes, including B cell development, premature aging and therapy resistance of certain cancers. Our own new findings, along with these recent developments in the field, will be highlighted.
Gokul Das, Ph.D.
Co-Director, Breast Disease Site Research Group, Roswell Park Cancer Institute, Buffalo, NY
Probing Estrogen Receptor−Tumor Suppressor p53 Interaction in Cancer: From Basic Research to Clinical Trial
Tumor suppressor p53 and estrogen receptor have opposite roles in the onset and progression of breast cancer. p53 responds to a variety of cellular of stresses by restricting the proliferation and survival of abnormal cells. Estrogen receptor plays an important role in normal mammary gland development and the preservation of adult mammary gland function; however, when deregulated it becomes abnormally pro-proliferative and greatly contributes to breast tumorigenesis. The biological actions of estrogens are mediated by two genetically distinct estrogen receptors (ERs): ER alpha and ER beta. In addition to its expression in several ER alpha-positive breast cancers and normal mammary cells, ER beta is usually present in ER alpha-negative cancers including triple-negative breast cancer. In spite of genetically being wild type, why p53 is functionally debilitated in breast cancer has remained unclear. Our recent finding that ER alpha binds directly to p53 and inhibits its function has provided a novel mechanism for inactivating genetically wild type p53 in human cancer. Using a combination of proliferation and apoptosis assays, RNAi technology, quantitative chromatin immunoprecipitation (qChIP), and quantitative real-time PCR (qRT-PCR), in situ proximity ligation assay (PLA), and protein expression analysis in patient tissue micro array (TMA), we have demonstrated binding of ER alpha to p53 and have delineated the domains on both the proteins necessary for the interaction. Importantly, ionizing radiation inhibits the ER-p53 interaction in vivo both in human cancer cells and human breast tumor xenografts in mice. In addition, antiestrogenstamoxifen and faslodex/fulvestrant (ICI 182780) disrupt the ER-p53 interaction and counteract the repressive effect of ER alpha on p53, whereas 17β-estradiol (E2) enhances the interaction. Intriguingly, E2 has diametrically opposite effects on corepressor recruitment to a p53-target gene promoter versus a prototypic ERE-containing promoter. Thus, we have uncovered a novel mechanism by which estrogen could be providing a strong proliferative advantage to cells by dual mechanisms: enhancing expression of ERE-containing pro-proliferative genes while at the same time inhibiting transcription of p53-dependent anti-proliferative genes. Consistently, ER alpha enhances cell cycle progression and inhibits apoptosis of breast cancer cells. Correlating with these observations, our retrospective clinical study shows that presence of wild type p53 in ER-positive breast tumors is associated with better response to tamoxifen therapy. These data suggest ER alpha-p53 interaction could be one of the mechanisms underlying resistance to tamoxifen therapy, a major clinical challenge encountered in breast cancer patients. We have launched a prospective clinical trial to analyze ER-p53 interaction in breast cancer patient tumors at Roswell Park Cancer Institute. Our more recent finding that ER beta has opposite functions depending on the mutational status of p53 in breast cancer cells is significant in understanding the hard-to-treat triple-negative breast cancer and in developing novel therapeutic strategies against it. Our integrated approach to analyze ER-p53 interaction at the basic, translational, and clinical research levels has major implications in the diagnosis, prognosis, and treatment of breast cancer.
Shrikant Anant, Ph.D.
The Department of Molecular & Integrative Physiology, Kansas University Medical Center, USA
Cancer Stem Cells: Target Colon Cancers
Shrikant Anant, Deep Kwatra and Dharmalingam Subramaniam
Colon cancer is a leading cause of cancer related deaths in the US, and its rate is increasing at an alarming rate in lndia. Recent studies have suggested the drug resistance role for a mall number of cells within a tumor called cancer stem cells. We identified the colon cancer stem cell marker DCLK1, a member of the protein kinase superfamily and the doublecortin family. The protein encodes a Cterminal serinethreonine protein kinase domain, which shows substantial homology to Ca2calmodulindependent protein kinase. Our current studies have been to identify compounds that can either affect DCLK1 expression or inhibits its activity as a way to inhibit cancer stem cells. Honokiol is a biphenolic compound that has been used in the traditional Chinese Medicine for treating various ailments. In vitro kinase assays with recombinant DCLK1 demonstrated that honokiol inhibits its kinase activity in a dose dependent manner. We therefore determined the effect of honokiol on stem cells. One method to look at effects on stem cells is perform a spheroid assay, where spheroids formation is suggested to maintain stemlike characteristic of cancer cells. Honokiol significantly suppressed colonosphere formation of two colon cancer cell lines HCT116 and SW480. Flow cytometry studies confirmed that honokiol reduced the number of DCLK1cells. A critical signaling pathway known to modulate intestinal stem cell proliferation is the Hippo signaling pathway, and deregulation of the pathway leads to tumor development. DCLK1cells had high levels of YAP1, the nuclear target of Hippo signaling. We determined the effect of honokiol on components of the hipposignaling pathway. Honokiol reduced the phosphorylation of Mst1/2, Lats1/2 and YAP1. Furthermore, honokiol treatment resulted in downregulation of YAPTEAD complex protein TEAD-1. Ectopic expression of the TEAD-1 partially rescued the cells from honokiol mediated growth suppression. To determine the effect of honokiol on tumor growth in vivo, nude mice harboring HCT116 tumor xenografts in their flanks were administered the compound intraperitoneally every day for 21 days. Honokiol treatment significantly inhibited tumor xenograft growth. Western blot and immunohistochemistry analyses demonstrated significant inhibition in the expression of stem marker and Hippo signaling proteins in the honokioltreated xenograft tissues. Taken together, these data suggest that honokiol is a potent inhibitor of colon cancer that targets DCLK1 stem cells by inhibiting Hippo signaling pathway.
Tanu Sharma, Narendra Parihar, Someshwar Nath, Azad Singh, Savneet Kaur, Simendra Singh and Chandi Mandal.
In the recent years, there has been a surge in various forms of cancers especially in urban areas of India. Tumor recurrence and metastasis are the main causes of increased morbidity and mortality. In poor and developing countries like India chemotherapy is the choosen method of therapeutic intervention for different types of malignancies such as breast, prostate, pancreas, etc. Although general chemotherapy treatment is effective in controlling tumour growth but high doses of the treatment regimen often results in severe off-target toxicity to different organs including liver, kidney, heart, brain etc. (1) A large percentage of patients are unable to tolerate this toxicity and sometime it can also lead to life threatening complications. (2) Therefore, the primary objective of this study is to prevent this druginduced off-target toxicity. Omega 3 fatty acids (n-3FAs) such as DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) that are active components of fish oil play active role in preventing cancer growth and its metastasis. (3â€“5) We have recently identified that omega 3-fatty acids prevent breast cancer bone metastasis by targeting cancer stem cell marker CD44 and osteoclastogenic factor CSF-1(4, 5). With this background, the present study addresses the role of n-3FAs in preventing chemotherapeutic drug-induced off-target toxicity.
The cat fishes were divided into four groups (each group contains 4 fishes) for each set of experiments. Three different chemotherapeutic drugs etoposide, doxorubicin, cisplatin at higher dosages (4, 2, 2 mg/kg body wt respectively) and fish oil (60mg/kg body wt, DHA: EPA; 2:3) were administered to cat fish (Mangur) by gavage. After 6 days, cat fishes were sacrificed and different organs were isolated. SGPT and alkaline phosphatase (ALP) activity assays were performed to examine liver function and superoxide dismutase activity (SOD) assay was conducted to evaluate reactive oxygen species (ROS) level.
Severe skin damages were observed both in doxorubicin and cisplatintreated cat fishes as compared to the control fishes, indicating side effects of chemotherapeutic drugs treatment. High level of SGPT as well as ALP activity was observed in liver samples of etoposide and doxorubicin â€“ treated fishes, suggesting chemotherapeutic drug-induced liver toxicity. Mechanistically, we found that doxorubicin treatment showed significant decrease of SOD activity in liver samples in comparison to the control fishes, suggesting that chemotherapeutic drugs lead to organ toxicity presumably by increasing ROS levels (6). However, treatment of the fishes with n-3FAs of the fish oil led to a dramatic reduction of chemotherapeutic drug-induced skin damages. Also, low levels of SGPT and ALP activities were observed in the fishes given etoposide in combination with n-3FAs as compared to the fishes given etoposide alone. Similarly, fish oil also gave protection against doxorubicin-induced liver dysfunction. Our data further showed that n-3FAs treatment significantly increased etoposide and doxorubicin-inhibited SOD activity.
The study for the first time reports that the use of n-3FAs leads to a dramatic reduction of chemotherapeutic drug-induced skin damages and mitigates chemotherapeutic drug-driven liver dysfunction presumably by reducing ROS level. This study suggests that n-3FAs may possibly be used in combination with chemotherapeutic drugs to treat different cancers to reduce chemotherapeutic drugs-associated systemic toxicity and to increase anticancer activity. Ongoing research study will further address the role of n-3FAs on other off-target toxic effects of chemotherapeutic drugs.
Tejaswini Subbannayya, Nandini A. Sahasrabuddhe, Arivusudar Marimuthu, Santosh Renuse, Gajanan Sathe, Srinivas M. Srikanth, Mustafa A. Barbhuiya, Bipin Nair, Juan Carlos Roa, Rafael Guerrero-Preston, H. C. Harsha, David Sidransky, Akhilesh Pandey, T. S. Keshava Prasad and Aditi Chatterjee
Proteomic profiling of gallbladder cancer secretome – a source for circulatory biomarker discovery
Gallbladder cancer (GBC) is the fifth most common cancer of the gastrointestinal tract and one of the common malignancies that occur in the biliary tract (Misra et al. 2006; Lazcano-Ponce et al. 2001). It has a poor prognosis with survival of less than 5 years in 90% of the cases (Misra et al. 2003). The etiology is ill-defined. Several risk factors have been reported including cholelithiasis, obesity, female gender and exposure to carcinogens (Eslick 2010; Kumar et al. 2006). Poor prognosis in GBC is mainly due to late presentation of the disease and lack of reliable biomarkers for early diagnosis. This emphasizes the need to identify and characterize cancer biomarkers to aid in the diagnosis and prognosis of GBC. Secreted proteins are an important class of molecules which can be detected in body fluids and has been targeted for biomarker discovery. There are challenges faced in the proteomic interrogation of body fluids especially plasma such as low abundance of tumor secreted proteins, high complexity and high abundance of other proteins that are not released by the tumor cells (Tonack et al. 2009). Profiling of conditioned media from the cancer cell lines can be used as an alternate means to identify secreted proteins from tumor cells (Kashyap et al. 2010; Marimuthu et al. 2012). We analyzed the invasive property of 7 GBC cell lines (SNU-308, G-415, GB-d1, TGBC2TKB, TGBC24TKB, OCUG-1 and NOZ). Four cell lines were selected for analysis of the cancer secretome based on the invasive property of the cells. We employed isobaric tags for relative and absolute quantitation (iTRAQ) labeling technology coupled with high resolution mass spectrometry to identify and characterize secretome from the panel of 4GBC cancer cells mentioned above. In total, we have identified around 2,000 proteins of which 175 were secreted at differential abundance across all the four cell lines. This secretome analysis will act as a reservoir of candidate biomarkers. Currently, we are investigating and validating these candidate markers from GBC cell secretome. Through this study, we have shown mass spectrometry-based quantitative proteomic analysis as a robust approach to investigate secreted proteins in cancer cells.