Targeted therapies: focus on a new strategy for gastrointestinal tumors

Hematopoietic derived cell infiltration of the intestinal tumor microenvironment in Apc Min/+ mice

Tumors consist of a heterogeneous population of neoplastic cells infiltrated by an equally heterogeneous collection of nonneoplastic cells that comprise the tumor microenvironment. Tumor growth, invasion, and metastasis depend on multiple interactions between these cells. To assess their potential as therapeutic targets or vehicles for tumor specific delivery of therapeutic agents, we examined the contribution of bone marrow derived cells (BMDCs) to the intestinal tumor microenvironment. Hematopoietic stem cells expressing the enhanced green fluorescent protein (eGFP) were transplanted into lethally irradiated ApcMin/+ mice, and their engraftment was analyzed by confocal microscopy. The results showed abundant infiltration of eGFP cells into the small intestine, colon, and spleen compared to heart, muscle, liver, lung, and kidney. Within the intestine, there was a pronounced gradient of engraftment along the anterior to posterior axis, with enhanced infiltration into adenomas. Immunofluorescence analysis showed that osteopontin was expressed in tumor stromal cells but not in nontumor stromal populations, suggesting that gene expression in these cells is distinct. Tumor vasculature in ApcMin/+ mice was chaotic compared to normal intestinal regions. Our data suggest that BMDCs can be harnessed for tumor-targeted therapies to enhance antitumor efficacy.

Locally advanced and metastatic sarcoma (adult type) including gastrointestinal stromal tumors

STS belong to the most challenging diseases in oncology that demand all resources of modern clinical oncology. With the improvement of surgical techniques and radiation therapy the majority of patients with localized disease can be cured. However, for patients with locally advanced or metastatic disease chemotherapeutic treatments have not greatly changed the poor outcome of the disease. The introduction of combined chemoradiotherapy as well as isolated limb-perfusion has improved the limb-salvage rate in locally advanced disease but the impact of systemic chemotherapy on overall survival remains a subject of dispute. For patients with metastatic sarcoma long-term survival can only be achieved in a small number of patients with mostly resectable disease. The list of effective drugs for palliative treatment in general still remains short and the duration of remissions usually does not exceed several months. The lack of alternative chemotherapeutic drugs imposes a considerable challenge in daily clinical practice with many young patients exhibiting a good performance status but progressive disease after standard treatment. A variety of new drugs or drug combinations seem to exhibit considerable activity in certain histological sarcoma subtypes, which may soon broaden the armamentarium of drugs for a subset of patients. However, with the vastly improved understanding of the biology and pathology of soft tissue sarcoma an era of opportunities seems to have begun and the recent success in the treatment of gastrointestinal stromal tumors impressively shows how fast a gain in the understanding of oncogenic mechanisms may translate into a highly efficient, clinically useful treatment.

Alphastatin downregulates vascular endothelial cells sphingosine kinase activity and suppresses tumor growth in nude mice bearing human gastric cancer xenografts

AIM: To investigate whether alphastatin could inhibit human gastric cancer growth and furthermore whether sphingosine kinase (SPK) activity is involved in this process.

METHODS: Using migration assay, MTT assay and Matrigel assay, the effect of alphastatin on vascular endothelial cells (ECs) was evaluated in vitro. SPK and endothelial differentiation gene (EDG)-1, -3, -5 mRNAs were detected by reverse transcription-polymerase chain reaction (RT-PCR). SPK activity assay was used to evaluate the effect of alphastatin on ECs. Matrigel plug assay in nude mice was used to investigate the effect of alphastatin on angiogenesis in vivo. Female nude mice were subcutaneously implanted with human gastric cancer cells (BGC823) for the tumor xenografts studies. Micro vessel density was analyzed in Factor VIII-stained tumor sections by the immunohistochemical SP method.

RESULTS: In vitro, alphastatin inhibited the migration and tube formation of ECs, but had no effect on proliferation of ECs. RT-PCR analysis demonstrated that ECs expressed SPK and EDG-1, -3, -5 mRNAs. In vivo, alphastatin sufficiently suppressed neovascularization of the tumor in the nude mice. Daily administration of alphastatin produced significant tumor growth suppression. Immunohistochemical studies of tumor tissues revealed decreased micro vessel density in alphastatin-treated animals as compared with controls.

CONCLUSION: Downregulating ECs SPK activity may be one of the mechanisms that alphastatin inhibits gastric cancer angiogenesis. Alphastatin might be a useful and relatively nontoxic adjuvant therapy in the treatment of gastric cancer.