Proliferation Rate Of Tumor Cells Research Articles

Image Guided Personalization of Reaction-Diffusion Type Tumor Growth Models Using Modified Anisotropic Eikonal Equations

Reaction-diffusion based tumor growth models have been widely used in the literature for modeling the growth of brain gliomas. Lately, recent models have started integrating medical images in their formulation. Including different tissue types, geometry of the brain and the directions of white matter fiber tracts improved the spatial accuracy of reaction-diffusion models. The adaptation of the general model to the specific patient cases on the other hand has not been studied thoroughly yet. In this paper, we address this adaptation. We propose a parameter estimation method for reaction-diffusion tumor growth models using time series of medical images. This method estimates the patient specific parameters of the model using the images of the patient taken at successive time instances. The proposed method formulates the evolution of the tumor delineation visible in the images based on the reaction-diffusion dynamics; therefore, it remains consistent with the information available. We perform thorough analysis of the method using synthetic tumors and show important couplings between parameters of the reaction-diffusion model. We show that several parameters can be uniquely identified in the case of fixing one parameter, namely the proliferation rate of tumor cells. Moreover, regardless of the value the proliferation rate is fixed to, the speed of growth of the tumor can be estimated in terms of the model parameters with accuracy. We also show that using the model-based speed, we can simulate the evolution of the tumor for the specific patient case. Finally, we apply our method to two real cases and show promising preliminary results.

Blocking effects of siRNA on VEGF expression in human colorectal cancer cells

To investigate the expression of vascular endothelial cell growth factor (VEGF) and its receptors Fms-like tyrosine kinase 1 (FLT-1) and fetal liver kinase 1 (FLK-1) in colorectal carcinoma (CRC), and the blocking effects of small interfering RNAs (siRNAs) on VEGF expression in human colorectal cancer HCT116 cells. Immunohistochemical staining for VEGF, FLT-1 and FLK-1 proteins was performed in 82 cases of CRC and 14 normal colorectal mucosae. A siRNA targeting VEGF was synthesized and transfected into HCT116 cells using lipofectamine 2000. Immunocytochemical staining and Western blotting analyses were performed to detect the expression of VEGF protein. The suppressive effect of the siRNA on cell proliferation was detected using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltertrazolium bromide (MTT) assay. Cellular apoptosis was detected using flow cytometry (FCM). The expression of VEGF, FLT-1 and FLK-1 in tumor tissues was significantly higher than that in normal tissues (P = 0.008, P = 0.000, P = 0.000). The expression of VEGF was positively correlated with both lymph node metastasis and clinical stage (P = 0.009 and P = 0.025, respectively). Immunocytochemistry showed that the expression of VEGF was weakly positive and Western blotting indicated a significant reduction in VEGF-siRNA cell protein levels. VEGF-siRNA cell growth inhibition was assessed by the MTT assay, and the tumor cell proliferation rate was significantly different at 24, 48, and 72 h after transfection. FCM results showed that the VEGF-siRNA group had an apparent aneuploid peak. VEGF, FLT-1 and FLK-1 are associated with colorectal carcinogenesis. siRNA silencing of the VEGF gene suppresses proliferation, and induces apoptosis in HCT116 cells. The results suggest that VEGF may be a new gene therapy target for colorectal cancer.

Abstract C109: NOV-002 suppresses tumor cell growth by modulating redox-sensitive cell signaling

Abstract Regulation of cell proliferation/survival is complex, impacted by multiple endogenous and exogenous stimuli capable of triggering overlapping and competing signaling pathways whose net effects can be quite cell dependent. Changes in redox status is one regulator of cell life/death decisions under both physiologic and pathologic conditions. Here we report on the anti-proliferative effects of a pharmacologically generated oxidative signal in human tumor cells using NOV-002, a glutathione disulfide-mimetic in advanced clinical trials for oncological indications. NOV-002 has demonstrated efficacy (increased survival and/or decreased tumor growth) in non-small cell lung, breast and ovarian cancers when combined with standard chemotherapeutic agents. In addition, treatment with NOV-002 mitigates chemotherapy-associated hematological toxicity. Pre-clinical data has linked this effect to proliferation of bone marrow progenitor cells subsequent to generation of an oxidative signal, intracellularly and at the cell surface of myeloid lineage cells, leading to activation of multiple kinases known to regulate cell proliferation (e.g. MAP kinases, JAK/STAT kinases). The data presented here extend redox modulation studies with NOV-002 to tumor cells. SKOV3 cells (a human ovarian tumor cell line) were exposed to NOV-002 (250 uM). Within 5 min after a single treatment, cellular levels of reactive oxygen species (ROS) were significantly elevated indicating the generation of an oxidative signal by NOV-002. This was not, however, sufficient to influence redox-sensitive cell signaling or tumor cell proliferation rate. In contrast, more prolonged exposure to NOV-002 (daily treatment for 5 days) resulted in a sustained elevation in ROS and dose-dependent activation of the proliferation-regulating MAP kinase, JNK, as evidenced by an increase in its active, phosphorylated form. Most importantly, this redox-activated cell signaling effect was associated with a significantly decreased proliferation rate of the SKOV3 cells that persisted even after stopping treatment with NOV-002. Thus, oxidative signal generation and MAP kinase pathway activation by NOV-002 appears to result in cell-type dependent effects on proliferation/survival. In myeloid lineage/bone marrow cells, chronic exposure to NOV-002 leads to increased proliferation while in tumor cells the result is a decrease in proliferation. These dichotomous effects may contribute to the unique clinical profile that NOV-002 has demonstrated to date — increased anti-tumor efficacy and survival combined with enhanced recovery from chemotherapy-induced hematological toxicity. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C109.

Development of Arterial Blood Supply in Experimental Liver Metastases

In this study, we present a mechanism for the development of arterial blood supply in experimental liver metastases. To analyze the arterialization process of experimental liver metastases, we elucidated a few key questions regarding the blood supply of hepatic lobules in mice. The microvasculature of the mouse liver is characterized by numerous arterioportal anastomoses and arterial terminations at the base of the lobules. These terminations supply one hepatic microcirculatory subunit per lobule, which we call an arterial hepatic microcirculatory subunit (aHMS). The process of arterialization can be divided into the following steps: 1) distortion of the aHMS by metastasis; 2) initial fusion of the sinusoids of the aHMS at the tumor parenchyma interface; 3) fusion of the sinusoids located at the base of the aHMSs, which leads to the disruption of the vascular sphincter (burst pipe); 4) incorporation of the dilated artery and the fused sinusoids into the tumor; and 5) further development of the tumor vasculature (arterial tree) by proliferation, remodeling, and continuous incorporation of fused sinusoids at the tumor-parenchyma interface. This process leads to the inevitable arterialization of liver metastases above the 2000- to 2500-mum size, regardless of the origin and growth pattern of the tumor.

Does dexamethasone inhibit anticancer activity of cetuximab in squamous cell carcinoma cell lines of the head and neck?

Glucocorticoids such as dexamethasone are widely used as comedication in the treatment of head and neck cancer, e.g., to improve appetite and decrease weight loss and fatigue in patients with advanced disease or as antiallergic and antiemetic prophylaxis during anti-EGFR therapy. However, the literature suggests that dexamethasone induces resistance to antineoplastic agents in many solid tumor models in vitro and in vivo. Since this phenomenon has never been investigated in head and neck cancer, the present study was conducted to investigate the effect of dexamethasone on the antiproliferative activity of cetuximab in vitro in squamous cell carcinoma of the head and neck (SCCHN) cell lines. The antiproliferative effect of the anti-EGFR agent cetuximab alone and in combination with increasing concentrations of dexamethasone was examined in eight SCCHN cell lines at three different time-points (24, 48 and 72 h). Cell growth inhibition and viability were measured quantitatively using WST and LDH assays. Absolute tumor cell numbers were determined by cell counting in a Rosenthal chamber. Cetuximab alone inhibited the growth of all eight SCCHN cell lines significantly (p=0.008). In some cases the addition of dexamethasone reduced the antiproliferative activity of cetuximab (p<or=0.038) but remained significant in all of the eight SCCHN cell lines compared with untreated controls (p<or=0.028) at each drug concentration and each time-point. In contrast to the results reported for other tumor models, in our study dexamethasone showed in the majority of the evaluated dexamethasone drug concentrations and time-points no inhibition of the cytotoxic activity of cetuximab. The reasons for these discrepant findings are unclear but may be related to the degree of tumor cell differentiation or proliferation rate. Thus, further studies are required to elucidate the molecular mechanisms underlying the interaction between dexamethasone and cetuximab in different tumors.

The effect of blue light exposure in an ocular melanoma animal model

BackgroundUveal melanoma (UM) cell lines, when exposed to blue light in vitro, show a significant increase in proliferation. In order to determine if similar effects could be seen in vivo, we investigated the effect of blue light exposure in a xenograft animal model of UM.MethodsTwenty New Zealand albino rabbits were injected with 1.0 × 106 human UM cells (92.1) in the suprachoroidal space of the right eye. Animals were equally divided into two groups; the experimental group was exposed to blue light, while the control group was protected from blue light exposure. The eyes were enucleated after sacrifice and the proliferation rates of the re-cultured tumor cells were assessed using a Sulforhodamine-B assay. Cells were re-cultured for 1 passage only in order to maintain any in vivo cellular changes. Furthermore, Proliferating Cell Nuclear Antigen (PCNA) protein expression was used to ascertain differences in cellular proliferation between both groups in formalin-fixed, paraffin-embedded eyes (FFPE).ResultsBlue light exposure led to a statistically significant increase in proliferation for cell lines derived from intraocular tumors (p < 0.01). PCNA expression was significantly higher in the FFPE blue light treated group when compared to controls (p = 0.0096).ConclusionThere is an increasing amount of data suggesting that blue light exposure may influence the progression of UM. Our results support this notion and warrant further studies to evaluate the ability of blue light filtering lenses to slow disease progression in UM patients.

Relaxin/RXFP1 Signaling in Prostate Cancer Progression

We found that relaxin peptide expression is significantly elevated in recurrent human prostate cancer. Stimulation with relaxin increased migration, invasiveness, proliferation, and adhesion of LNCaP and PC3 cells in vitro. Opposite effects on cellular phenotype were observed after suppression of endogenous relaxin/RXFP1 expression or signaling. We showed an accelerated progression of prostate cancer in TRAMP males with transgenic relaxin overexpression and a longer survival of TRAMP, RXFP1-deficient males. Suppression of RXFP1 expression in PC3 xenografts in nude mice by intratumoral injections of short interfering RNA resulted in decreased tumor size, cell proliferation, and metastasis rate.

Asymptotic behavior of solutions of a free boundary problem modelling the growth of tumors with Stokes equations

We study a free boundary problem modelling the growth of non-necrotic tumors with fluid-like tissues. The fluid velocity satisfies Stokes equations with a source determined by the proliferation rate of tumor cells which depends on the concentration of nutrients, subject to a boundary condition with stress tensor effected by surface tension. It is easy to prove that this problem has a unique radially symmetric stationary solution. By using a functional approach, we prove that there exists a threshold value γ* > 0 for the surface tension coefficient $\gamma$, such that in the case γ > γ* this radially symmetric stationary solution is asymptotically stable under small non-radial perturbations, whereas in the opposite case it is unstable.

Effects of combination treatment of bortezomib and dexamethasone in SCCHN cell lines depend on tumor cell specificity.

Bortezomib has recently become the new treatment standard for relapsed or refractory multiple myeloma. We previously demonstrated that bortezomib also had a significant growth-inhibiting and apoptotic effect on squamous cell carcinoma of the head and neck (SCCHN) cells in vitro. Preclinical evidence has provided a rationale for combining bortezomib with dexamethasone in multiple myeloma, suggesting that the therapeutic effects of the two agents might be additive. These findings are in contrast with the results achieved in solid tumor models where the addition of dexamethasone reduced the efficacy of other antineoplastic drugs. In the present study, we investigated the effect of dexamethasone in combination with bortezomib in SCCHN cell lines for the first time. The antiproliferative effect of bortezomib alone or in combination with increasing concentrations of dexamethasone was investigated in four SCCHN cell lines. Cell growth inhibition and viability were measured quantitatively using WST and LDH assays. Bortezomib alone inhibited the growth of all four SCCHN cell lines significantly (p<0.047). The addition of dexamethasone leads to a clear tumor cell decline and showed a trend in enhancing the growth-inhibitory effect of bortezomib although the difference failed to reach statistical significance (p>0.05). Our first results show that dexamethasone increased the cytotoxic activity of bortezomib in most SCCHN cell lines investigated. These findings might be dependent on molecular factors such as the degree of tumor cell differentiation and proliferation rate. Therefore, further studies will be required to elucidate these molecular factors to substantiate our findings from a cancer biological point of view.

Relationship Between Vascular Endothelial Growth Factor and Nuclear Factor-κB in Renal Cell Tumors

To assess the relationship between protein and messenger RNA (mRNA) levels of vascular endothelial growth factor (VEGF) and subcellular localization of nuclear factor-kappa B (NF-kappaB), proliferation rate of tumor cells, and clinicopathological characteristics of renal cell tumors. We analyzed 31 one renal cell tumors - 22 clear cell renal cell carcinomas (CCRCC) and 9 other histologic types (non-CCRCC). VEGF expression and subcellular localization of p65 member of NF-kappaB and Ki67 were immunohistochemically evaluated for the proliferation rate of tumor cells. Expression of VEGF mRNA was assessed using quantitative real-time polymerase chain reaction after total RNA extraction from snap-frozen tumor tissue samples. Cytoplasmic localization of VEGF protein in renal cell tumors showed a perimembranous and diffuse pattern, the former being more evident in CCRCC (27.1 -/+ 18.9 vs 3.3 -/+ 10 % tumors, P<0.001) and the latter in non-CCRCC type (71.7 -/+ 23.2 vs 31.1 -/+ 22.1 % tumors, P<0.001). Heterogeneity in VEGF gene expression was more pronounced in CCRCC type than in non-CCRCC type (P=0.004). In addition, perimembranous VEGF pattern was associated with higher VEGF mRNA levels (P=0.006) and diffuse VEGF pattern with lower VEGF mRNA levels (P<0.001). Nuclear and cytoplasmic staining of NF-kappaB/p65 was observed in the majority of tumor cells. A significant association was recorded between cytoplasmic NK-kappaB/65 staining and VEGF staining of diffuse pattern (P=0.026). Association between NF-kappaB/65 and proliferation rate of tumor cells was significant for cytoplasmic staining (P=0.039) but not for nuclear NFkB/p65 staining (P=0.099). Higher but inhomogeneous expression of VEGF in tumor cells, especially in CCRCCs, is associated with NF-kappaB/65 activity. This indicates that both VEGF and NF-kappaB/65 may be important in renal carcinogenesis, representing a possible molecular target in the treatment of renal cell carcinoma.

Centrosomal PKCβII and Pericentrin Are Critical for Human Prostate Cancer Growth and Angiogenesis

Angiogenesis is critical in the progression of prostate cancer. However, the interplay between the proliferation kinetics of tumor endothelial cells (angiogenesis) and tumor cells has not been investigated. Also, protein kinase C (PKC) regulates various aspects of tumor cell growth, but its role in prostate cancer has not been investigated in detail. Here, we found that the proliferation rates of endothelial and tumor cells oscillate asynchronously during the growth of human prostate cancer xenografts. Furthermore, our analyses suggest that PKCbetaII was activated during increased angiogenesis and that PKCbetaII plays a key role in the proliferation of endothelial cells and tumor cells in human prostate cancer; treatment with a PKCbetaII-selective inhibitor, betaIIV5-3, reduced angiogenesis and tumor cell proliferation. We also find a unique effect of PKCbetaII inhibition on normalizing pericentrin (a protein regulating cytokinesis), especially in endothelial cells as well as in tumor cells. PKCbetaII inhibition reduced the level and mislocalization of pericentrin and normalized microtubule organization in the tumor endothelial cells. Although pericentrin has been known to be up-regulated in epithelial cells of prostate cancers, its level in tumor endothelium has not been studied in detail. We found that pericentrin is up-regulated in human tumor endothelium compared with endothelium adjacent to normal glands in tissues from prostate cancer patients. Our results suggest that a PKCbetaII inhibitor such as betaIIV5-3 may be used to reduce prostate cancer growth by targeting both angiogenesis and tumor cell growth.

Imaging of Cell Proliferation: Status and Prospects

Increased cellular proliferation is an integral part of the cancer phenotype. Several in vitro assays have been developed to measure the rate of tumor growth, but these require biopsies, which are particularly difficult to obtain over time and in different areas of the body in patients with multiple metastatic lesions. Most of the effort to develop imaging methods to noninvasively measure the rate of tumor cell proliferation has focused on the use of PET in conjunction with tracers for the thymidine salvage pathway of DNA synthesis, because thymidine contains the only pyrimidine or purine base that is unique to DNA. Imaging with 11C-thymidine has been tested for detecting tumors and tracking their response to therapy in animals and patients. Its major limitations are the short half-life of 11C and the rapid catabolism of thymidine after injection. These limitations led to the development of analogs that are resistant to degradation and can be labeled with radionuclides more conducive to routine clinical use, such as 18F. At this point, the thymidine analogs that have been studied the most are 3'-deoxy-3'-fluorothymidine (FLT) and 1-(2'-deoxy-2'-fluoro-1-beta-d-arabinofuranosyl)-thymine (FMAU). Both are resistant to degradation and track the DNA synthesis pathway. FLT is phosphorylated by thymidine kinase 1, thus being retained in proliferating cells. It is incorporated by the normal proliferating marrow and is glucuronidated in the liver. FMAU can be incorporated into DNA after phosphorylation but shows less marrow uptake. It shows high uptake in the normal heart, kidneys, and liver, in part because of the role of mitochondrial thymidine kinase 2. Early clinical data for 18F-FLT demonstrated that its uptake correlates well with in vitro measures of proliferation. Although 18F-FLT can be used to detect tumors, its tumor-to-normal tissue contrast is generally lower than that of 18F-FDG in most cancers outside the brain. The most promising use for thymidine and its analogs is in monitoring tumor treatment response, as demonstrated in animal studies and pilot human trials. Further work is needed to determine the optimal tracer(s) and timing of imaging after treatment.

Influence of Cell Proportions and Proliferation Rates on FDG Uptake in Squamous-Cell Esophageal Carcinoma: A PET Study

We investigated the influence of cell proportions and proliferation activities on tumor maximum standard uptake value (SUV(max)) in patients with squamous-cell esophageal cancer (SCEC). Sixteen (16) patients with untreated SCEC were examined with (18)F-flourodeoxyglucose positron emission tomography (FDG-PET). The tumor SUV(max) were calculated. Tumors were resected by transthoracic esophagectomy. Tissues were stained with hematoxylin and eosin for the measurement of cell proportions and MIB-1 for measurement of proliferation indices (PIs). Tumor SUV and histologic data were related by using multiple linear regression analysis. The mean proportion of tumor cells in the tumor site was 58.1% (+/-12.1%); the proportion of inflammatory cells was 34.2% (+/-14.2%); the PI of tumor cells was 70.5% (+/-11.8%); and the PI of inflammatory cells was 22.2% (+/-7.6%). The tumor PI was the only variable that was significantly associated with the FDG uptake in the tumor site (p = 0.04). The correlation was low (Pearson-coefficient Gamma = 0.51). The Pearson-correlation-coefficient between tumor SUV and the fraction of inflammatory cells was Gamma = 0.37 and between tumor SUV and PI of inflammatory cells Gamma = 0.13. In untreated SCEC-patients, the tumor maximum FDG uptake is weakly associated with the proliferation rate of tumor cells. In contrast, neither the proportion nor the PI of inflammatory cells in the tumor site significantly correlates with the maximum SUV and should not profoundly affect PET interpretations.

Anatomical Differences in Response to Angiogenesis

Ten angiogenesis inhibitors are currently approved by the FDA in the U.S., to treat cancer and age‐related macular degeneration, and by regulatory agencies in &gt;30 other countries.1 1,257,600 patients received prescriptions for these angiogenesis inhibitors during 2006.2 40 other antiangiogenic drugs are in late Phase III or Phase II clinical trials. Significant increases in survival have been reported for colorectal cancer, lung cancer and breast cancer. Of patients with progressive macular degeneration, 95% gain improved eyesight, and of those who are blind, 40% regain sight.3These clinical successes have increased the need to understand basic mechanisms of angiogenesis even beyond the level of detail that was necessary to discover angiogenesis inhibitors in the first place.One example is the differential result of angiogenic responses at different anatomic sites. In an animal model of human ovarian cancer, 5 of 5 tumor types in the lower abdominal cavity remain non‐angiogenic and do not grow beyond 1 mm.3 Tumors in the upper abdomen, are angiogenic and continue to expand to 140‐fold larger mass than lower abdominal tumors. The tumor cell proliferation rate is the same at both sites, but apoptosis is higher in non‐angiogenic tumors. In thrombospondin‐1 null mice all tumors in the lower abdomen become angiogenic and grow to an equivalent size as those in the upper abdomen. If both thrombospondin and endostatin are knocked out, the lower abdominal tumors are not only angiogenic, but are 3 times larger than the upper abdominal tumors.Conclusion: Potent endogenous angiogenesis inhibitors are differentially distributed in the stroma according to anatomical site.

CO2 pneumoperitoneum increases systemic but not local tumor spread after intraperitoneal murine neuroblastoma spillage in mice

Minimally invasive techniques are increasingly used for biopsy and resection of neuroblastoma, but the impact on the behavior of spilled tumor cells is unknown. We aimed to investigate whether CO(2) pneumoperitoneum can affect local or systemic tumor manifestation after spillage of neuroblastoma cells into the peritoneal cavity. Murine neuroblastoma cells (Neuro2a, 1x10(6)) were inoculated into the peritoneal cavity of 25 male A/J mice, which subsequently underwent CO(2) pneumoperitoneum (n = 12) or laparotomy (n = 13) for 1 h. At the 28th postoperative day, local (peritoneal and surface of the gut) and systemic (liver, lung, spine) tumor spread was graded in a blinded manner (1-4 point scale) and specimens were histologically examined for tumor manifestation (hematoxylin and eosin stain) and tumor cell proliferation rate (Ki-67-stain). In the case of no visible lesion, five random sections were histologically examined. Peritoneal carcinosis was graded macroscopically. Tumor manifestations were detected in 10 out of 12 (83%) animals after CO(2) pneumoperitoneum, and in 9 out of 13 (69%) after laparotomy (n.s.). Incidence of liver metastasis was higher after CO(2) pneumoperitoneum versus laparotomy (83% versus 31%; p < 0.05). Incidence and grading of peritoneal carcinosis was not significantly different between the groups (n.s.). Intrapulmonary metastasis was found in one mouse of each group, but no metastasis of the spine. However, the grading of liver metastasis was higher after CO(2) pneumoperitoneum compared to laparotomy (p < 0.05). Tumor cell proliferation (Ki-67 stain) in the liver did not differ between both groups. Moreover, proliferation always exceeded 50% of tumor cells, irrespective local or systemic tumor manifestation. CO(2) pneumoperitoneum increased intrahepatic metastasis, but not local peritoneal carcinosis in a murine neuroblastoma model. This suggests that laparoscopy could promote systemic dissemination of intraperitoneally spilled tumor cells when no chemotherapy is applied. It remains to be determined whether this is due to local immune suppression or direct modulation of tumor cell behavior.

Therapeutic metformin/AMPK activation promotes the angiogenic phenotype in the ERα negative MDA-MB-435 breast cancer model

Metformin, a first line treatment for type 2 diabetes, has been implicated as a potential anti-neoplastic agent for breast cancers as well as other cancers. Metformin is known to work in part through the activation of AMP-dependent kinase (AMPK). AMPK is a key regulator of cellular energy homeostasis, especially under stress conditions where biosynthetic pathways are blocked by the phosphorylation of downstream AMPK substrates. Stimulation of AMPK by metformin resulted in a significant repression of cell proliferation and active MAPK1/2 in both estrogen receptor alpha (ERalpha) negative (MDA-MB-231, MDA-MB-435) and positive (MCF-7, T47D) human breast cancer cell lines. However, when ERalpha negative MDA-MB-435 cells were treated with metformin, they demonstrated increased expression of vascular endothelial growth factor (VEGF) in an AMPK dependent manner; while the ERalpha positive MCF-7 cells did not. Systemic therapy with metformin was tested for efficacy in an orthotopic model of ERalpha negative breast cancer performed in athymic nude mice. Surprisingly, metformin therapy significantly improved tumorigenic progression as compared to untreated controls. The metformin-treated group showed increased VEGF expression, intratumoral microvascular density and reduced necrosis. Metformin treatment was sufficient, however, to reduce systemic IGF-1 and the proliferation rate of tumor cells in vascularized regions. The data presented here suggests that, although metformin significantly represses breast cancer cell growth in vitro, the efficacy with respect to its therapeutic application for ERalpha negative breast cancer lesions in vivo may result in promotion of the angiogenic phenotype and increased tumorigenic progression.

Protein tyrosine phosphatase epsilon and Neu-induced mammary tumorigenesis

Aberrant regulation of the phosphorylation of proteins on tyrosine residues is a well-established cause of cancer. Protein tyrosine phosphatases (PTPs) share in the crucial function of maintaining appropriate levels of phosphorylation of cellular proteins, making them potentially key players in regulating the transformation process. The receptor-type tyrosine phosphatase Epsilon (RPTPepsilon) participates in supporting the transformed phenotype of mammary tumor cells induced in vivo by the Neu tyrosine kinase. The phosphatase is overexpressed in mammary tumors induced in mice by a Neu transgene and expression of RPTPepsilon in mouse mammary glands leads to massive hyperplasia and associated tumorigenesis. Furthermore, cells isolated from mammary tumors induced by Neu in mice genetically lacking RPTPepsilon appear less transformed and proliferate less well than corresponding mammary tumor cells isolated from mice expressing the phosphatase. At the molecular level, RPTPepsilon dephosphorylates and activates Src and the related kinases Yes and Fyn, and the activities of these kinases are significantly reduced in tumor cells lacking RPTPepsilon. Restoring the activities of these kinases reveals that it is only the reduced activity of Src that causes the aberrant morphology and proliferation rate of tumor cells lacking RPTPepsilon. RPTPepsilon is primed to activate Src, and presumably related kinases, following its phosphorylation by Neu at Y695 within its C-terminus. This event is crucial in enabling RPTPepsilon to activate Src, but appears not to affect the activity of RPTPepsilon towards unrelated substrates. We conclude that a Neu-RPTPepsilon-Src pathway exists in mouse mammary tumor cells, in which Neu phosphorylates RPTPepsilon thereby driving the phosphatase to specifically activate Src family kinases and to assist in maintaining the transformed phenotype.

Imatinib Mesylate Enhances Therapeutic Effects of Gemcitabine in Human Malignant Mesothelioma Xenografts

Platelet-derived growth factor receptor beta (PDGFRbeta), frequently activated in malignant mesothelioma, is a promising cancer therapeutic target. Imatinib mesylate (STI571; Glivec) is a selective inhibitor of tyrosine kinases as bcr-abl, c-kit, c-fms, and PDGFRbeta and enhances tumor drug uptake by reducing the interstitial fluid pressure. We previously showed that imatinib mesylate synergizes with gemcitabine and pemetrexed in PDGFRbeta-positive mesothelioma cells. Here, we aimed at investigating these combined treatments in a novel mesothelioma model. REN mesothelioma cells, infected with a lentiviral vector carrying the luciferase gene, were injected in the peritoneum of severe combined immunodeficient mice. This model allowed imaging of live animals treated with pemetrexed or gemcitabine chemotherapeutics, or with imatinib mesylate alone, as well as with a combination of gemcitabine and imatinib mesylate. We show here that, consistent with our previous in vitro studies, gemcitabine inhibited tumor growth, whereas pemetrexed was ineffective, even at the highest dosage tested. Compared with monotreatment, the combination of gemcitabine with imatinib mesylate led to a further tumor growth inhibition and improved mice survival, by a decrease rate of tumor cell proliferation and an increase in number of apoptotic tumor cells. Imatinib mesylate enhances the therapeutic response to gemcitabine, in accordance with our previous in vitro data. These in vivo results validate imatinib mesylate and gemcitabine as a combination treatment of malignant mesothelioma, also in view of its known positive effects on tumor drug uptake. These evidences provide the rationale for the currently ongoing clinical trials.

Oncologic Impact of Surgery in the Early Postoperative Period

Surgical intervention represents a deliberate form of tissue injury producing the acute phase response. The response to injury is also associated with a period of relative immune suppression and the magnitude of the response is proportional to the degree of surgical trauma. The proinflammatory cascade of events produced by the response to injury coupled with a impairment of postoperative cell-mediated immune function may provide a stimulus for the progression of neoplastic disease. There is strong evidence from animal studies that all types of abdominal surgical procedures are associated with increased rates of systemic tumor establishment and growth postoperatively. In preclinical models, minimally invasive techniques have been shown to ameliorate the effects of surgically induced tumor progression. This pattern of tumor behavior was noted following sham operations and after bowel resections. The precise mechanism of these changes remains unclear; however, both an increased rate of tumor cell proliferation and a decreased apoptosis have been noted after open surgery. There is also evidence that the cell-mediated immunosuppression that has been documented to occur after surgery accounts for some of the differences in tumor growth after open versus laparoscopic surgery. Systemic plasma factors elaborated following laparotomy have also been associated with increased tumor cell proliferation in vitro, suggesting that it may prove possible to pharmacologically protect patients from the deleterious side effects of surgery on postoperative tumor proliferation.

Exisulind in Combination with Celecoxib Modulates Epidermal Growth Factor Receptor, Cyclooxygenase-2, and Cyclin D1 against Prostate Carcinogenesis:In vivoEvidence

Nonsteroidal anti-inflammatory drugs mediate anticancer effects by modulating cyclooxygenase-2 (COX-2)-dependent and/or COX-2-independent mechanism(s); however, the toxicity issue is a concern with single agents at higher doses. In this study, we determined the combined effect of celecoxib, a COX-2 inhibitor, along with exisulind (sulindac sulfone/Aptosyn) at low doses in prostate cancer. We used a sequential regimen of N-methyl-N-nitrosourea + testosterone to induce prostate cancer in Wistar-Unilever rats. Following carcinogen treatment, celecoxib and exisulind individually and their combination at low doses were given in NIH-07 diet for 52 weeks. We determined the incidence of prostatic intraepithelial neoplasia, adenocarcinomas, rate of tumor cell proliferation, and apoptosis. Immunohistochemical and Western blot analysis were done to determine COX-2, epidermal growth factor receptor (EGFR), Akt, androgen receptor, and cyclin D1 expression. Serum prostaglandin E2 and tumor necrosis factor-alpha levels were determined using enzyme immunoassay/ELISA assays. The rats that received celecoxib in combination with exisulind at low doses showed a significant decrease in prostatic intraepithelial neoplasia and adenocarcinomas as well as an enhanced rate of apoptosis. An overall decrease in COX-2, EGFR, Akt, androgen receptor, and cyclin D1 expression was found associated with tumor growth inhibition. Reduced serum levels of COX-2 protein, prostaglandin E2, and tumor necrosis factor-alpha indicated anti-inflammatory effects. A strong inhibition of total and phosphorylated form of EGFR (Tyr(992) and Tyr(845)) and Akt (Ser(473)) was significant in rats given with these agents in combination. In this study, we show for the first time that the combination of celecoxib with exisulind at low doses could prevent prostate carcinogenesis by altering key molecular events.