Kusum Rathore

Animal models and therapeutic molecular targets of cancer: utility and limitations.

Cancer is the term used to describe over 100 diseases that share several common hallmarks. Despite prevention, early detection, and novel therapies, cancer is still the second leading cause of death in the USA. Successful bench-to-bedside translation of basic scientific findings about cancer into therapeutic interventions for patients depends on the selection of appropriate animal experimental models. Cancer research uses animal and human cancer cell lines in vitro to study biochemical pathways in these cancer cells. In this review, we summarize the important animal models of cancer with focus on their advantages and limitations. Mouse cancer models are well known, and are frequently used for cancer research. Rodent models have revolutionized our ability to study gene and protein functions in vivo and to better understand their molecular pathways and mechanisms. Xenograft and chemically or genetically induced mouse cancers are the most commonly used rodent cancer models. Companion animals with spontaneous neoplasms are still an underexploited tool for making rapid advances in human and veterinary cancer therapies by testing new drugs and delivery systems that have shown promise in vitro and in vivo in mouse models. Companion animals have a relatively high incidence of cancers, with biological behavior, response to therapy, and response to cytotoxic agents similar to those in humans. Shorter overall lifespan and more rapid disease progression are factors contributing to the advantages of a companion animal model. In addition, the current focus is on discovering molecular targets for new therapeutic drugs to improve survival and quality of life in cancer patients.

Green tea catechin intervention of reactive oxygen species-mediated ERK pathway activation and chronically induced breast cell carcinogenesis

Long-term exposure to low doses of environmental carcinogens contributes to sporadic human breast cancers. Epidemiologic and experimental studies indicate that green tea catechins (GTCs) may intervene with breast cancer development. We have been developing a chronically induced breast cell carcinogenesis model wherein we repeatedly expose non-cancerous, human breast epithelial MCF10A cells to bioachievable picomolar concentrations of environmental carcinogens, such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P), to progressively induce cellular acquisition of cancer-associated properties, as measurable end points. The model is then used as a target to identify non-cytotoxic preventive agents effective in suppression of cellular carcinogenesis. Here, we demonstrate, for the first time, a two-step strategy that initially used end points that were transiently induced by short-term exposure to NNK and B[a]P as targets to detect GTCs capable of blocking the acquisition of cancer-associated properties and subsequently used end points constantly induced by long-term exposure to carcinogens as targets to verify GTCs capable of suppressing carcinogenesis. We detected that short-term exposure to NNK and B[a]P resulted in elevation of reactive oxygen species (ROS), leading to Raf-independent extracellular signal-regulated kinase (ERK) pathway activation and subsequent induction of cell proliferation and DNA damage. These GTCs, at non-cytotoxic levels, were able to suppress chronically induced cellular carcinogenesis by blocking carcinogen-induced ROS elevation, ERK activation, cell proliferation and DNA damage in each exposure cycle. Our model may help accelerate the identification of preventive agents to intervene in carcinogenesis induced by long-term exposure to environmental carcinogens, thereby safely and effectively reducing the health risk of sporadic breast cancer.

Grape Seed Proanthocyanidin Suppression of Breast Cell Carcinogenesis Induced by Chronic Exposure to Combined 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanone and Benzo[a]Pyrene

Breast cancer is the most common type of cancer among women in northern America and northern Europe; dietary prevention is a cost‐efficient strategy to reduce the risk of this disease. To identify dietary components for the prevention of human breast cancer associated with long‐term exposure to environmental carcinogens, we studied the activity of grape seed proanthocyanidin extract (GSPE) in suppression of cellular carcinogenesis induced by repeated exposures to low doses of environmental carcinogens. We used combined carcinogens 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanone (NNK) and benzo[a]pyrene (B[a]P), at picomolar concentrations, to repeatedly treat noncancerous, human breast epithelial MCF10A cells to induce cellular acquisition of cancer‐related properties of reduced dependence on growth factors, anchorage‐independent growth, and acinar‐conformational disruption. Using these properties as biological target endpoints, we verified the ability of GSPE to suppress combined NNK‐ and B[a]P‐induced precancerous cellular carcinogenesis and identified the minimal, noncytotoxic concentration of GSPE required for suppressing precancerous cellular carcinogenesis. We also identified that hydroxysteroid‐11‐beta‐dehydrogenase 2 (HSD11B2) may play a role in NNK‐ and B[a]P‐induced precancerous cellular carcinogenesis, and its expression may act as a molecular target endpoint in GSPEs suppression of precancerous cellular carcinogenesis. And, the ability of GSPE to reduce gene expression of cytochrome‐P450 enzymes CYP1A1 and CYP1B1, which can bioactivate NNK and B[a]P, possibly contributes to the preventive mechanism for GSPE in suppression of precancerous cellular carcinogenesis. Our model system with biological and molecular target endpoints verified the value of GSPE for the prevention of human breast cell carcinogenesis induced by repeated exposures to low doses of multiple environmental carcinogens.

Green tea catechin extract in intervention of chronic breast cell carcinogenesis induced by environmental carcinogens

Sporadic breast cancers are mainly attributable to long‐term exposure to environmental factors, via a multi‐year, multi‐step, and multi‐path process of tumorigenesis involving cumulative genetic and epigenetic alterations in the chronic carcinogenesis of breast cells from a non‐cancerous stage to precancerous and cancerous stages. Epidemiologic and experimental studies have suggested that green tea components may be used as preventive agents for breast cancer control. In our research, we have developed a cellular model that mimics breast cell carcinogenesis chronically induced by cumulative exposures to low doses of environmental carcinogens. In this study, we used our chronic carcinogenesis model as a target system to investigate the activity of green tea catechin extract (GTC) at non‐cytotoxic levels in intervention of cellular carcinogenesis induced by cumulative exposures to pico‐molar 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanone (NNK) and benzo[a]pyrene (B[a]P). We identified that GTC, at a non‐cytotoxic, physiologically achievable concentration of 2.5 µg/mL, was effective in suppressing NNK‐ and B[a]P‐induced cellular carcinogenesis, as measured by reduction of the acquired cancer‐associated properties of reduced dependence on growth factors, anchorage‐independent growth, increased cell mobility, and acinar‐conformational disruption. We also detected that intervention of carcinogen‐induced elevation of reactive oxygen species (ROS), increase of cell proliferation, activation of the ERK pathway, DNA damage, and changes in gene expression may account for the mechanisms of GTCs preventive activity. Thus, GTC may be used in dietary and chemoprevention of breast cell carcinogenesis associated with long‐term exposure to low doses of environmental carcinogens.

Differential induction of reactive oxygen species through Erk1/2 and Nox-1 by FK228 for selective apoptosis of oncogenic H-Ras-expressing human urinary bladder cancer J82 cells

PurposeThis study sought to reveal mechanisms for differential regulation of reactive oxygen species (ROS) in histone deacetylase inhibitor FK228-induced selective apoptosis of oncogenic H-Ras-expressing human cancer cells.MethodsHuman urinary bladder cancer J82 and oncogenic H-Ras-expressing J82 cells were used to reveal FK228-induced differential Erk1/2 activation, Nox-1 elevation, ROS production, glutathione (GSH) depletion, caspase activation, and apoptosis. Specific inhibitors were used to suppress Nox-1 activity and ROS production. Mek1/2 inhibitor was used to suppress Erk1/2 activation. Validated-specific siRNAs were used to knock down Nox-1. ROS levels, GSH levels, and caspase-3/7 activities were measured by GSH assay, flow cytometry and luminescence assays, respectively. Western blot analysis determined levels of Erk1/2 and Nox-1.ResultsErk1/2, Nox-1, ROS, caspase-3/7, and cell death were differentially induced, whereas GSH was differentially depleted by FK228 in oncogenic H-Ras-expressing J82 versus parental cells. Blockage of the ERK pathway resulted in suppressing oncogenic H-Ras- and FK228-induced Nox-1 elevation, ROS production, caspase activation, and cell death. Knockdown of Nox-1 by specific siRNAs reduced FK228-induced ROS production, caspase activation, and cell death.ConclusionOncogenic H-Ras expression and FK228 treatment synergistically induced the ERK pathway, resulting in differentially increased Nox-1 elevation, ROS production, and GSH depletion, leading to differential caspase activation and cell death in oncogenic H-Ras-expressing J82 versus parental cells.

Molecular Imaging of Cyclooxygenase-2 in Canine Transitional Cell Carcinomas In Vitro and In Vivo.

The enzyme COX-2 is induced at high levels in tumors but not in surrounding normal tissues, which makes it an attractive target for molecular imaging of cancer. We evaluated the ability of novel optical imaging agent, fluorocoxib A to detect urinary bladder canine transitional cell carcinomas (K9TCC). Here, we show that fluorocoxib A uptake overlapped with COX-2 expression in primary K9TCC cells in vitro. Using subcutaneously implanted primary K9TCC in athymic mice, we show specific uptake of fluorocoxib A by COX-2–expressing K9TCC xenograft tumors in vivo. Fluorocoxib A uptake by COX-2–expressing xenograft tumors was blocked by 70% (P < 0.005) when pretreated with the COX-2 selective inhibitor, celecoxib (10 mg/kg), 4 hours before intravenous administration of fluorocoxib A (1 mg/kg). Fluorocoxib A was taken up by COX-2–expressing tumors but not by COX-2–negative human UMUC-3 xenograft tumors. UMUC-3 xenograft tumors with no expression of COX-2 showed no uptake of fluorocoxib A. In addition, fluorocoxib A uptake was evaluated in five dogs diagnosed with TCC. Fluorocoxib A specifically detected COX-2–expressing K9TCC during cystoscopy in vivo but was not detected in normal urothelium. Taken together, our findings show that fluorocoxib A selectively bound to COX-2–expressing primary K9TCC cells in vitro, COX-2–expressing K9TCC xenografts tumors in nude mice, and heterogeneous canine TCC during cystoscopy in vivo. Spontaneous cancers in companion animals offer a unique translational model for evaluation of novel imaging and therapeutic agents using primary cancer cells in vitro and in heterogeneous cancers in vivo. Cancer Prev Res; 6(5); 466–76. ©2013 AACR.

Mesenchymal and stem-like cell properties targeted in suppression of chronically-induced breast cell carcinogenesis

Stem-like cells and the epithelial-to-mesenchymal transition (EMT) program are postulated to play important roles in various stages of cancer development, but their roles in breast cell carcinogenesis and intervention remain to be clarified. We investigated stem-like cell- and EMT-associated properties and markers in breast epithelial cells chronically exposed to low-dose 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and benzo[a]pyrene in the presence and absence of the preventive agents green tea catechins and grape seed extract. Our results indicate that stem-like cell- and EMT-associated properties and markers should be seriously considered as new cancer-associated indicators for detecting breast cell carcinogenesis and as endpoints for intervention of carcinogenesis.

Piroxicam inhibits Masitinib-induced cyclooxygenase 2 expression in oral squamous cell carcinoma cells in vitro

Development and characterization of animal models for human cancers is important for the improvement of diagnosis and therapy. The oral squamous cell carcinoma (OSCC) of domestic animals resembles human OSCC in many aspects; thus, cell lines derived from OSCC of cats and dogs are a valuable model for human OSCC. We characterized 1 feline OSCC (FeOSCC-Sidney) and 1 canine OSCC (K9OSCC-Abby) cell line and compared their characteristics with human OSCC cell line hSCC-25. We calculated the doubling time of the new OSCC cell lines and evaluated the expression profiles of cancer-related markers and cell-cycle proteins such as c-kit, platelet-derived growth factor receptor, vascular endothelial growth factor receptor, epidermal growth factor receptor, cyclooxygenase (COX)-1, COX-2, and p27 by immunocytochemistry and Western blot analysis. We evaluated the effects of novel receptor tyrosine kinase inhibitor (Masitinib, AB1010) and the nonsteroidal anti-inflammatory drug piroxicam on the previously mentioned OSCC cells. Interestingly, AB1010 increased expression levels of COX-2 in all tested OSCCs. Cotreatment of piroxicam with Masitinib significantly inhibited cell proliferation of OSCC as compared to either drug alone through the c-kit and AKT signaling pathways. Piroxicam inhibited Masitinib-induced COX-2 expression in all tested OSCCs. Therefore, targeting these two signaling pathways simultaneously was more efficient for inhibition of OSCCs across these species.

FK228 and oncogenic H-Ras synergistically induce Mek1/2 and Nox-1 to generate reactive oxygen species for differential cell death

To investigate the mechanism behind the pro-apoptotic ability of oncogenic H-Ras to enhance FK228-induced apoptosis, we primarily used the 10T1/2-TR-H-Ras cell line, in which ectopic expression of oncogenic H-Ras(V12) is controlled by the addition of tetracycline into cultures, and secondarily used oncogenic H-Ras-expressing MCF10A cells in our studies. Our results showed the pro-apoptotic roles of Mek1/2 activation, nicotinamide adenine dinucleotide phosphate-oxidase 1 (Nox-1) elevation, and reactive oxygen species (ROS) production in FK228-induced selective cell death of oncogenic H-Ras-expressing cells versus counterpart cells. We found that although Nox-1 elevation and ROS production played essential roles in oncogenic H-Ras-induced cell proliferation and morphological transformation, the expression of oncogenic H-Ras and FK228 treatment synergistically induced activation of Mek1/2. This activation resulted in differentially increased Nox-1 elevation and ROS production leading to selective cell death of oncogenic H-Ras-expressing cells versus counterpart cells. We also found that FK228 treatment induced mitochondrial ROS and Mek1/2 activation, bypassing Raf-1, to downstream Erk1/2, participating in the induction of selective cell death. Thus, the pro-apoptotic abilities of Mek1/2 and Nox-1 should be considered as potential targets in designing therapeutic protocols using FK228 to assure ROS-mediated cell death for treating cancer cells acquiring Ras activation.

Animal model of naturally occurring bladder cancer: Characterization of four new canine transitional cell carcinoma cell lines

BackgroundDevelopment and further characterization of animal models for human cancers is important for the improvement of cancer detection and therapy. Canine bladder cancer closely resembles human bladder cancer in many aspects. In this study, we isolated and characterized four primary transitional cell carcinoma (K9TCC) cell lines to be used for future in vitro validation of novel therapeutic agents for bladder cancer.MethodsFour K9TCC cell lines were established from naturally-occurring canine bladder cancers obtained from four dogs. Cell proliferation rates of K9TCC cells in vitro were characterized by doubling time. The expression profile of cell-cycle proteins, cytokeratin, E-cadherin, COX-2, PDGFR, VEGFR, and EGFR were evaluated by immunocytochemistry (ICC) and Western blotting (WB) analysis and compared with established human bladder TCC cell lines, T24 and UMUC-3. All tested K9TCC cell lines were assessed for tumorigenic behavior using athymic mice in vivo.ResultsFour established K9TCC cell lines: K9TCC#1Lillie, K9TCC#2Dakota, K9TCC#4Molly, and K9TCC#5Lilly were confirmed to have an epithelial-cell origin by morphology analysis, cytokeratin, and E-cadherin expressions. The tested K9TCC cells expressed UPIa (a specific marker of the urothelial cells), COX-2, PDGFR, and EGFR; however they lacked the expression of VEGFR. All tested K9TCC cell lines confirmed a tumorigenic behavior in athymic mice with 100% tumor incidence.ConclusionsThe established K9TCC cell lines (K9TCC#1Lillie, K9TCC#2Dakota, K9TCC#4Molly, and K9TCC#5Lilly) can be further utilized to assist in development of new target-specific imaging and therapeutic agents for canine and human bladder cancer.