Interleukin 12 and indomethacin exert a synergistic, angiogenesis-dependent antitumor activity in mice

Proteasome inhibition potentiates antitumor effects of photodynamic therapy in mice through induction of endoplasmic reticulum stress and unfolded protein response

Photodynamic therapy (PDT) is an approved therapeutic procedure that exerts cytotoxic activity toward tumor cells by inducing production of reactive oxygen species such as singlet oxygen. PDT leads to oxidative damage of cellular macromolecules, including proteins that undergo multiple modifications such as fragmentation, cross-linking, and carbonylation that result in protein unfolding and aggregation. Because the major mechanism for elimination of carbonylated proteins is their degradation by proteasomes, we hypothesized that a combination of PDT with proteasome inhibitors might lead to accumulation of carbonylated proteins in endoplasmic reticulum (ER), aggravated ER stress, and potentiated cytotoxicity toward tumor cells. We observed that Photofrin-mediated PDT leads to robust carbonylation of cellular proteins and induction of unfolded protein response. Pretreatment of tumor cells with three different proteasome inhibitors, including bortezomib, MG132, and PSI, gave increased accumulation of carbonylated and ubiquitinated proteins in PDT-treated cells. Proteasome inhibitors effectively sensitized tumor cells of murine (EMT6 and C-26) as well as human (HeLa) origin to PDT-mediated cytotoxicity. Significant retardation of tumor growth with 60% to 100% complete responses was observed in vivo in two different murine tumor models (EMT6 and C-26) when PDT was combined with either bortezomib or PSI. Altogether, these observations indicate that combination of PDT with proteasome inhibitors leads to potentiated antitumor effects. The results of these studies are of immediate clinical application because bortezomib is a clinically approved drug that undergoes extensive clinical evaluations for the treatment of solid tumors.

Cyclooxygenase inhibition in early onset of tumor growth and related angiogenesis evaluated in EP1 and EP3 knockout tumor-bearing mice

It is well established that prostanoids are essential for local inflammation including cell proliferation and apoptosis. Accordingly, prostaglandin E2 (PGE(2)) is a critical factor in wound healing, tumor invasiveness and progression. Therefore, the aim of the present work was to evaluate effects by PGE(2) on tumor vascular density at early onset of tumor growth where hypoxia is limited. Wild-type mice (C57Bl, C3H/HeN) bearing either MCG-101 tumors or a malignant melanoma (K1735-M2) with either high or insignificant PGE(2) production and subsequently different in sensitivity to cyclooxygenase (COX) inhibition were used. Tumor angiogenesis was estimated by intravital microscopy and immune histochemical analysis in wild type and EP(1) or EP(3) subtype receptor knockout mice (C57Bl). Both MCG-101 and K1735-M2 tumor cells stimulated early outgrowth of tumor vessels in proportion to intrinsic growth rate of tumor cells. Indomethacin had no effects on tumor growth or tumor related vascular area in K1735-M2 bearing mice. By contrast, indomethacin decreased tumor cell proliferation and increased apoptosis in MCG-101 tumors with subsequent adaptation in tumor vascular density. Effects of indomethacin on early growth of MCG-101 tumors were not related to tumor content of bFGF protein, while our earlier studies on long-term tumor growth have shown decreased mRNA levels of bFGF during indomethacin treatment. Early onset of tumor growth was significantly promoted in EP(3)- but not in EP(1)-knockouts, although long-term tumor growth is attenuated in EP(1)-knockouts as reported elsewhere. Our results demonstrate that tumor production of PGE(2) promotes primarily net growth of tumor cells with subsequent adaptations in development of the tumor vasculature. Therefore, it is likely that angiogenesis is not a limiting step at the early onset of tumor growth.

Effect of indomethacin on cell cycle proteins in colon cancer cell lines

AIM: To study the effect of indomethacin (IN) on human colon cancer cell line SW480 with p53 mutant and SW480 transfected wild-type p53 (wtp53/SW480) in vitro and investigate molecular mechanism of anti-tumor effect of IN on colon cancer.

METHODS: SW480 cells and wtp53/SW480 cells were treated with different concentrations of IN respectively, the expressions of CDK₂, CDK4 and p21^WAF1/CIP1 protein were detected by Western blotting.

RESULTS: IN gradually down-regulated the expression of CDK₂, CDK4 protein of wtp53/SW480 cells in a dose-dependent manner, and inhibitory effect reached the maximum level at 600 μmol/L; IN up-regulated the expression of p21^WAF1/CIP1 protein in a dose-dependent manner at a certain concentration range, and the expression reached the maximum level at 400 μmol/L, and returned to the base level at 600 μmol/L. The expression of CDK₂, CDK4 and p21^WAF1/CIP1 protein of SW480 cells did not change.

CONCLUSION: IN exerts antitumor effect partly through down regulation of the expression of CDK₂, CDK4 protein and up regulation of the expression of p21^WAF1/PIC1.

Colorectal cancer chemoprevention--an overview of the science

The development and dissemination of sophisticated detection technologies have recently exposed the high prevalence of preinvasive colorectal neoplasia in the adult U.S. population. Although cancer screening and surveillance provide opportunities for risk stratification, they achieve risk reduction only when coupled with effective interventions. This review surveys the lead compounds for colorectal cancer prevention and the measures by which they may be prioritized for clinical testing. Clinical trials remain the rate-limiting step in agent development, and novel trial designs are needed to hasten agent identification and testing for cancer prevention. Innovative research models include the nesting of prevention end points within cancer treatment trials and within trials testing promising preventive compounds intended for nononcologic indications.

Activity of the non-steroidal anti-inflammatory drug indomethacin against colorectal cancer

A substantial body of evidence from rodent colon carcinogenesis models, in vitro experiments with human colorectal cancer cells and limited clinical observations in humans suggest that the non-steroidal anti-inflammatory drug indomethacin has anti-colorectal cancer activity. However, although many mechanisms of the anti-neoplastic activity of indomethacin have been suggested, e.g., cyclooxygenase inhibition and peroxisome proliferator-activated receptor gamma activation, the precise relevance of the majority of in vitro pharmacological observations to the in vivo anti-neoplastic activity of indomethacin remains unclear. Herein, we review the existing literature describing the chemopreventative and chemotherapeutic efficacy of indomethacin against colorectal cancer, and draw together the disparate literature describing potential mechanisms of action of indomethacin in human colorectal cancer cells in vitro. Although indomethacin itself has significant adverse effects, including serious upper gastrointestinal toxicity, the development of novel derivatives that may have an improved safety profile means that further investigation of the anti-colorectal cancer activity of indomethacin is warranted.

The future of colon cancer prevention

Chemoprevention science is in flux owing to rapid advances in postgenomic technology. We have witnessed enormous advances in the areas of early detection and molecular profiling of colorectal carcinogenesis; however, unique interpretive and technologic challenges persist. Neoplastic hallmarks must be iteratively tested and validated as markers of risk, targets for intervention, and/or markers of response in order to expedite the development of preventive interventions. In this review, we highlight several of the technologies that are revolutionizing our understanding of carcinogenesis and our approach to colorectal cancer prevention.

Morphologic analysis of microvessels in colorectal tumors with respect to the formation of liver metastases

BACKGROUND AND OBJECTIVES

Overexpression of VEGF and proliferation of microvessels are strongly related to liver metastases, however, morphologic analyses of microvessels in liver metastases have not been reported. The purpose of the present study was to examine the correlation between liver metastases and the diameters of microvessel lumens in the tumor tissue.

METHODS

Fifty-nine patients with liver metastases from colorectal cancers and 112 patients who underwent curative colorectal resection and survived without any recurrence were reviewed. Microvessel density (MVD) and the diameters of the lumens of individual microvessels were assessed.

RESULTS

There was a significant difference in terms of the mean MVD of primary tumors between patients with liver metastases and those without liver metastases. The numbers of patients with liver metastases who had microvessels 100-200 microm in diameter and microvessels more than 200 microm in diameter were significantly greater than patients without liver metastases. Microvessels with lumens more than 100 microm in diameter were not detected in the liver metastatic lesion.

CONCLUSION

Large microvessels in the primary tumor favor intravasation of cancer cells.