Modulation of fatty acid metabolism and immune suppression are features of in vitro tumour sphere formation in ontogenetically distinct dog cancers

Non-adherent, 3-dimensional sphere formation is used as an in vitro surrogate to evaluate cellular potential for tumour initiation and self-renewal. To determine if a shared molecular program underlies the capacity for sphere formation by cells originating from diverse tumour types, we characterized molecular and functional properties of 10 independent cell lines derived from 3 ontogenetically distinct dog cancers: hemangiosarcoma, osteosarcoma and glial brain tumours. Genome-wide gene expression profiling identified tumour-of-origin-dependent patterns of adjustment to sphere formation in a uniform culture condition. However, expression of the stem/progenitor markers CD34 and CD117, resistance to cytotoxic drugs and dye efflux (side population assays) showed no association with these gene expression profiles. Instead, primary sphere-forming capacity was inversely correlated with the ability to reform secondary spheres, regardless of tumour ontogeny. Primary sphere formation seemed to be proportional to the number of pre-existing cells with sphere-forming capacity in the cell lines. Cell lines where secondary sphere formation was more proficient than primary sphere formation showed enrichment of genes involved in fatty acid synthesis and immunosuppressive cytokines. In contrast, cell lines where secondary sphere formation was approximately equivalent to or less proficient than primary sphere formation showed upregulation of CD40 and enrichment of genes involved in fatty acid oxidation. Our data suggest that in vitro sphere formation is associated with upregulation of gene clusters involved in metabolic and immunosuppressive functions, which might be necessary for self-renewal and for tumour initiation and/or tumour propagation in vivo.

Molecular profiling reveals prognostically significant subtypes of canine lymphoma

We performed genomewide gene expression analysis of 35 samples representing 6 common histologic subtypes of canine lymphoma and bioinformatics analyses to define their molecular characteristics. Three major groups were defined on the basis of gene expression profiles: (1) low-grade T-cell lymphoma, composed entirely by T-zone lymphoma; (2) high-grade T-cell lymphoma, consisting of lymphoblastic T-cell lymphoma and peripheral T-cell lymphoma not otherwise specified; and (3) B-cell lymphoma, consisting of marginal B-cell lymphoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Interspecies comparative analyses of gene expression profiles also showed that marginal B-cell lymphoma and diffuse large B-cell lymphoma in dogs and humans might represent a continuum of disease with similar drivers. The classification of these diverse tumors into 3 subgroups was prognostically significant, as the groups were directly correlated with event-free survival. Finally, we developed a benchtop diagnostic test based on expression of 4 genes that can robustly classify canine lymphomas into one of these 3 subgroups, enabling a direct clinical application for our results.

P2-01-03: Insulin-Like Growth Factor I (IGF) Induced Metastasis Signature Correlates with Poor Prognosis and Decreased Distant Metastasis-Free Survival in Human Breast Cancer

The insulin-like growth factors (IGFs) acting via the type I insulin-like growth factor receptor (IGF-1R) regulate tumor growth, survival and metastasis of multiple types of cancers. Agents targeting IGF-1R are currently being tested in phase II/III clinical trials in human cancers. We have previously reported that IGF1R can regulate metastasis independently of primary tumor growth in a model of high risk metastatic breast cancer using the triple negative MDA435/LCC6 metastatic cancer cells, which form spontaneous lung metastases when injected into the mammary fat pad of mice. We have shown that disruption of IGF signaling either with an antibody against IGF1R, AVE1642, or a dominant negative IGF-1R construct, does not affect growth in the mammary fat pad but inhibits pulmonary metastases and colonization of the lungs. Regulation of such a phenotype will not be measured in clinical trials and these findings imply that clinical trials of this therapeutic strategy may need to adjust their endpoints for assessing benefit by taking into account that inhibition of IGF1R signaling may inhibit metastasis but not primary tumor growth. Here, we sought to develop an IGF induced metastasis signature that may be useful in selecting patients that could benefit from IGF1R targeted therapy and determine if changes in expression of the genes in the signature can be useful in monitoring response. Serum starved LCC6-WT cells (with wild-type functional IGF1R) and LCC6-DN (cells with dominant negative IGF1R) were treated with IGF-I, AVE1642 (fully human antibody against IGF1R that inhibits metastasis but not tumor growth in the mammary fat pad), or AVE1642+ IGF-I for 4 and 24 hours and microarray analysis was performed using the U133 Plus 2.0 human arrays with 47,000 transcripts. IGF-I regulated over 100 transcripts in LCC6-WT cells compared to IGF-I in LCC6-DN cells. Over 400 transcripts were basally differentially expressed in LCC6-WT cells compared to LCC6-DN cells. Array data were also analyzed to determine genes regulated by IGF-I signaling in LCC6-WT cells compared to untreated LCC6-WT cells and if disruption of signaling with AVE1642 affected genes whose expression was regulated by IGF-I signaling. A total of 263 transcripts were regulated by IGF signaling in LCC6-WT cells compared to untreated cells and AVE1642 treatment reversed the regulation of all transcripts induced by IGF-I in LCC6-WT cells. 53 of the most significantly regulated genes were used to query two different human breast tumor datasets to determine if genes in IGF signaling induced metastasis signature are associated with lymph node metastasis and poor prognosis in human tumors. IGF regulated metastasis signature genes were expressed in human tumors in the van't Veer and Wang datasets. Further, IGF activated metastasis signature was correlated to decreased survival and decreased distant metastasis free survival in breast cancer patients. Our results suggest that presence of IGF induced metastasis signature in patients confers prognostic value and identifying IGF driven metastasis signatures may be useful to identify and monitor patients who could benefit from IGF1R targeted therapy for inhibition of metastatic disease.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-01-03.