Cancer-associated fibroblasts actively compress cancer cells and modulate mechanotransduction

During tumor progression, cancer-associated fibroblasts (CAFs) accumulate in tumors and produce an excessive extracellular matrix (ECM), forming a capsule that enwraps cancer cells. This capsule acts as a barrier that restricts tumor growth leading to the buildup of intratumoral pressure. Combining genetic and physical manipulations in vivo with microfabrication and force measurements in vitro, we found that the CAFs capsule is not a passive barrier but instead actively compresses cancer cells using actomyosin contractility. Abrogation of CAFs contractility in vivo leads to the dissipation of compressive forces and impairment of capsule formation. By mapping CAF force patterns in 3D, we show that compression is a CAF-intrinsic property independent of cancer cell growth. Supracellular coordination of CAFs is achieved through fibronectin cables that serve as scaffolds allowing force transmission. Cancer cells mechanosense CAF compression, resulting in an altered localization of the transcriptional regulator YAP and a decrease in proliferation. Our study unveils that the contractile capsule actively compresses cancer cells, modulates their mechanical signaling, and reorganizes tumor morphology.

Optimized protocol for the generation of an orthotopic colon cancer mouse model and metastasis

The microenvironment plays an essential role in tumor development and metastatic progression. Here, we describe a simple and rapid protocol to generate tumors in mice using colon cancer cell lines or tumoroids in the correct microenvironment, colonic mucosa. We also detail steps for monitoring the growth of the primary tumor in real time using colonoscopy or in vivo imaging system, as well as monitoring metastasis development. Finally, we describe tissue collection and sample preparation for subsequent immunohistochemistry analysis.

Paracrine signalling between intestinal epithelial and tumour cells induces a regenerative programme

Tumours are complex ecosystems composed of different types of cells that communicate and influence each other. While the critical role of stromal cells in affecting tumour growth is well established, the impact of mutant cancer cells on healthy surrounding tissues remains poorly defined. Here, using mouse intestinal organoids, we uncover a paracrine mechanism by which intestinal cancer cells reactivate foetal and regenerative YAP-associated transcriptional programmes in neighbouring wildtype epithelial cells, rendering them adapted to thrive in the tumour context. We identify the glycoprotein thrombospondin-1 (THBS1) as the essential factor that mediates non-cell-autonomous morphological and transcriptional responses. Importantly, Thbs1 is associated with bad prognosis in several human cancers. This study reveals the THBS1-YAP axis as the mechanistic link mediating paracrine interactions between epithelial cells in intestinal tumours.

Spontaneous mouse lymphoma in patient-derived tumor xenografts: The importance of systematic analysis of xenografted human tumor tissues in preclinical efficacy trials

Patient-derived tumor xenograft (PDX) is now largely recognized as a key preclinical model for cancer research, mimicking patient tumor phenotype and genotype. Immunodeficient mice, well-known to develop spontaneous lymphoma, are required for PDX growth. As for all animal models used for further clinical translation, a robust experimental design is strongly required to lead to conclusive results. Here we briefly report unintentional co-engraftment of mouse lymphoma during expansion of well-established PDXs to illustrate the importance of systematic check of the PDX identity to avoid misinterpretation. Besides, this quality control based on complementary approaches deserves a more detailed description in materials and methods section to ensure experimental validity and reproducibility.

Active cell migration is critical for steady-state epithelial turnover in the gut

Steady-state turnover is a hallmark of epithelial tissues throughout adult life. Intestinal epithelial turnover is marked by continuous cell migration, which is assumed to be driven by mitotic pressure from the crypts. However, the balance of forces in renewal remains ill-defined. Combining biophysical modeling and quantitative three-dimensional tissue imaging with genetic and physical manipulations, we revealed the existence of an actin-related protein 2/3 complex-dependent active migratory force, which explains quantitatively the profiles of cell speed, density, and tissue tension along the villi. Cells migrate collectively with minimal rearrangements while displaying dual-apicobasal and front-back-polarity characterized by actin-rich basal protrusions oriented in the direction of migration. We propose that active migration is a critical component of gut epithelial turnover.

Cancer cells in the tumor core exhibit spatially coordinated migration patterns

In the early stages of metastasis, cancer cells exit the primary tumor and enter the vasculature. Although most studies have focused on the tumor invasive front, cancer cells from the tumor core can also potentially metastasize. To address cell motility in the tumor core, we imaged tumor explants from spontaneously forming tumors in mice in real time using long-term two-photon microscopy. Cancer cells in the tumor core are remarkably dynamic and exhibit correlated migration patterns, giving rise to local 'currents' and large-scale tissue dynamics. Although cells exhibit stop-and-start migration with intermittent pauses, pausing does not appear to be required during division. Use of pharmacological inhibitors indicates that migration patterns in tumors are actively driven by the actin cytoskeleton. Under these conditions, we also observed a relationship between migration speed and correlation length, suggesting that cells in tumors are near a jamming transition. Our study provides new insight into the dynamics of cancer cells in the tumor core, opening new avenues of research in understanding the migratory properties of cancer cells and later metastasis.This article has an associated First Person interview with the first author of the paper.

Array comparative genomic hybridization identifies high level of PI3K/Akt/mTOR pathway alterations in anal cancer recurrences

Genomic alterations of anal squamous cell carcinoma (ASCC) remain poorly understood due to the rarity of this tumor. Array comparative genomic hybridization and targeted gene sequencing were performed in 49 cases of ASCC. The most frequently altered regions (with a frequency greater than 25%) were 10 deleted regions (2q35, 2q36.3, 3p21.2, 4p16.3, 4p31.21, 7q36.1, 8p23.3, 10q23.2, 11q22.3, and 13q14.11) and 8 gained regions (1p36.33, 1q21.1, 3q26.32, 5p15.33, 8q24.3, 9q34.3, 16p13.3, and 19p13.3). The most frequent minimal regions of deletion (55%) encompassed the 11q22.3 region containing ATM, while the most frequent minimal regions of gain (57%) encompassed the 3q26.32 region containing PIK3CA. Recurrent homozygous deletions were observed for 5 loci (ie, TGFR2 in 4 cases), and recurrent focal amplifications were observed for 8 loci (ie, DDR2 and CCND1 in 3 cases, respectively). Several of the focal amplified genes are targets for specific therapies. Integrated analysis showed that the PI3K/Akt/mTOR signaling pathway was the pathway most extensively affected, particularly in recurrences compared to treatment‐naive tumors (64% vs 30%; P = .017). In patients with ASCC recurrences, poor overall survival (OS) was significantly correlated with a large number of altered regions (P = .024). These findings provide insight into the somatic genomic alterations in ASCC and highlight the key role of the druggable PI3K/Akt/mTOR signaling pathway.

The early pregnancy placenta foreshadows DNA methylation alterations of solid tumors

The placenta relies on phenotypes that are characteristic of cancer to successfully implant the embryo in the uterus during early pregnancy. Notably, it has to invade its host tissues, promote angiogenesis—while surviving hypoxia—, and escape the immune system. Similarities in DNA methylation patterns between the placenta and cancers suggest that common epigenetic mechanisms may be involved in regulating these behaviors. We show here that megabase-scale patterns of hypomethylation distinguish first from third trimester chorionic villi in the placenta, and that these patterns mirror those that distinguish many tumors from corresponding normal tissues. We confirmed these findings in villous cytotrophoblasts isolated from the placenta and identified a time window at the end of the first trimester, when these cells come into contact with maternal blood, as the likely time period for the methylome alterations. Furthermore, the large genomic regions affected by these patterns of hypomethylation encompass genes involved in pathways related to epithelial-mesenchymal transition, immune response, and inflammation. Analyses of expression profiles corresponding to genes in these hypomethylated regions in colon adenocarcinoma tumors point to networks of differentially expressed genes previously implicated in carcinogenesis and placentogenesis, where nuclear factor kappa B is a key hub. Taken together, our results suggest the existence of epigenetic switches involving large-scale changes of methylation in the placenta during pregnancy and in tumors during neoplastic transformation. The characterization of such epigenetic switches might lead to the identification of biomarkers and drug targets in oncology as well as in obstetrics and gynecology.

Cancer-associated fibroblasts lead tumor invasion through integrin-β3-dependent fibronectin assembly

Cancer-associated fibroblasts (CAFs) promote cancer cell invasion and dissemination by remodeling the extracellular matrix; however, the mechanism by which CAFs remodel the matrix is still unknown. Attieh et al. show that CAFs induce cancer cell invasion through fibronectin matrix assembly that is mainly mediated by integrin-αvβ3.

Cancer-associated fibroblasts (CAFs) are the most abundant cells of the tumor stroma. Their capacity to contract the matrix and induce invasion of cancer cells has been well documented. However, it is not clear whether CAFs remodel the matrix by other means, such as degradation, matrix deposition, or stiffening. We now show that CAFs assemble fibronectin (FN) and trigger invasion mainly via integrin-αvβ3. In the absence of FN, contractility of the matrix by CAFs is preserved, but their ability to induce invasion is abrogated. When degradation is impaired, CAFs retain the capacity to induce invasion in an FN-dependent manner. The level of expression of integrins αv and β3 and the amount of assembled FN are directly proportional to the invasion induced by fibroblast populations. Our results highlight FN assembly and integrin-αvβ3 expression as new hallmarks of CAFs that promote tumor invasion.

Clinical value of R-spondins in triple-negative and metaplastic breast cancers

Background:

RSPO ligands, activators of the Wnt/β-catenin pathway, are overexpressed in different cancers. The objective of this study was to investigate the role of RSPOs in breast cancer (BC).

Methods:

Expression of RSPO and markers of various cancer pathways were measured in breast tumours and cell lines by qRT–PCR. The effect of RSPO on the Wnt/β-catenin pathway activity was determined by luciferase assay, western blotting, and qRT–PCR. The effect of RSPO2 inhibition on proliferation was determined by using RSPO2 siRNAs. The effect of IWR-1, an inhibitor of the Wnt/β-catenin pathway, was examined on the growth of an RSPO2-positive patient-derived xenograft (PDX) model of metaplastic triple-negative BC.

Results:

We detected RSPO2 and RSPO4 overexpression levels in BC, particularly in triple-negative BC (TNBC), metaplastic BC, and triple-negative cell lines. Various mechanisms could account for this overexpression: presence of fusion transcripts involving RSPO, and amplification or hypomethylation of RSPO genes. Patients with RSPO2-overexpressing tumours have a poorer metastasis-free survival (P=3.6 × 10⁻⁴). RSPO2 and RSPO4 stimulate Wnt/β-catenin pathway activity. Inhibition of RSPO expression in a TN cell line inhibits cell growth, and IWR-1 significantly inhibits the growth of an RSPO2-overexpressing PDX.

Conclusions:

RSPO overexpression could therefore be a new prognostic biomarker and therapeutic target for TNBC.

Abstract 2762: Common DNA methylation patterns in cancer and placental cells involved in migration and invasion, immune escape, and angiogenesis induction

Identifying common patterns of regulation in cancer and placental cells might shed new light on cellular programs allowing aggressive tumor development. Indeed, as it has been described for the first time more than a century ago, cancer and placental cells (trophoblasts) share astonishingly similar phenotypes : migration and invasion, immune escape, and angiogenesis induction. These common phenotypes, relying on common genomic sequences and transcriptomic profiles, may result from a shared epigenomic regulation program. This might be especially true for tumor cells leading eventually to metastasis and cytotrophoblasts (a trophoblasts subset) during placental implantation at the beginning of pregnancy.

In order to investigate such common epigenomic patterns, we carried out comparisons of DNA methylation in cancer and placental cell genomes. This study involved: cancer samples (primary tumor vs. normal tissue) across various tissues (including breast, colon, liver, lung, prostate, thyroid, uterus), on one hand; and placenta samples (early vs. late term) either heterogeneous (chorionic villi) or homogenous (ex vivo cytotrophoblasts), on the other hand. Cancer data were data downloaded from The Cancer Genome Atlas web portal. Placenta data were downloaded from the Gene Expression Omnibus web portal. In addition, our group generated original data from ex vivo cytotrophoblasts samples. All data were generated on the Illumina Infinium 450K array. Data analysis was carried out thanks to computational methods for epigenomics recently described.

This first direct comparison of cancer and placental cells epigenomes, leveraging both published data and original data, led to the identification of large hypomethylated blocks common to cancer and placental cells. Such common patterns have recently been described as a universal defining epigenetic alteration in human solid tumors. These megabase-scale DNA methylation marks differentiate primary tumors from normal tissues. Likewise, they differentiate early term placentas from late term placentas. Moreover, genes belonging to genomic regions displaying common large hypomethylated blocks overlapping in cancers and placentas are enriched for pathways involved in migration and invasion, immune escape, and angiogenesis induction.

Common DNA methylation patterns in cancer and placental cells identified in this pilot study might contribute to the epigenomic regulation of cellular programs allowing aggressive tumor development. Further analyses of these common patterns, as well as analyses of differences in cancer and placental cell epigenomes, could eventually lead to the identification of critical epigenomic switches that prevent healthy placentas to degenerate into tumors, while they allow aggressive tumors to develop. Ultimately, such epigenomic switches could also represent innovative targets in oncology.

Citation Format: Akpeli V. Nordor, Sophie Richon, Thierry Fournier, Dominique Bellet, Virginie Dangles-Marie, Martin J. Aryee. Common DNA methylation patterns in cancer and placental cells involved in migration and invasion, immune escape, and angiogenesis induction. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2762.

Evaluating patient-derived colorectal cancer xenografts as preclinical models by comparison with patient clinical data

Development of targeted therapeutics required translationally relevant preclinical models with well-characterized cancer genome alterations. Here, by studying 52 colorectal patient-derived tumor xenografts (PDX), we examined key molecular alterations of the IGF2-PI3K and ERBB-RAS pathways and response to cetuximab. PDX molecular data were compared with that published for patient colorectal tumors in The Cancer Genome Atlas. We demonstrated a significant pattern of mutual exclusivity of genomic abnormalities in the IGF2-PI3K and ERBB-RAS pathways. The genomic anomaly frequencies observed in microsatellite stable PDX reproduce those detected in nonhypermutated patient tumors. We found frequent IGF2 upregulation (16%), which was mutually exclusive with IRS2, PIK3CA, PTEN, and INPP4B alterations, supporting IGF2 as a potential drug target. In addition to maintaining the genomic and histologic diversity, correct preclinical models need to reproduce drug response observed in patients. Responses of PDXs to cetuximab recapitulate also clinical data in patients, with partial or complete response in 15% (8 of 52) of PDXs and response strictly restricted to KRAS wild-type models. The response rate reaches 53% (8 of 15) when KRAS, BRAF, and NRAS mutations are concomitantly excluded, proving a functional cross-validation of predictive biomarkers obtained retrospectively in patients. Collectively, these results show that, because of their clinical relevance, colorectal PDXs are appropriate tools to identify both new targets, like IGF2, and predictive biomarkers of response/resistance to targeted therapies.

Specific detection of type II human chorionic gonadotropin beta subunit produced by trophoblastic and neoplastic cells

BACKGROUND

The sequence of the beta-subunit of human chorionic gonadotropin (hCGβ) varies depending on whether hCGβ is encoded by type I or type II genes. Type II genes are upregulated in trophoblast and cancer but hCGβ can be detected in the serum of nonpregnant women and healthy individuals. We aimed to determine whether monoclonal antibody (mAb) FBT11-II specifically detects hCGβ encoded by type II genes (type II hCGβ).

METHODS

Competitive inhibition assays with synthetic peptides, immunocytochemical and immunohistochemical studies, type II hCGβ dosing immunoassays and sequencing of CGB genes were performed.

RESULTS

Competitive inhibition assays determined that mAb FBT11-II recognizes the type II hCGβ derived peptide. CGB mRNA sequencing of JEG-3 (trophoblastic) and T24 (bladder) cell lines confirmed that JEG-3 expresses type II genes while T24 expresses exclusively type I. FBT11-II only recognizes JEG-expressed hCGβ. Placenta immunohistochemical studies confirmed that type II hCGβ expression is restricted to the syncytiotrophoblast. Immunoassays detected type II hCGβ in serum of patients with either nontrophoblastic cancers or fetal Down syndrome.

CONCLUSION

Type II gene expression can be detected using FBT11-II. This specific recognition could improve the clinical usefulness of assays aimed at either managing aggressive tumors or screening for Down syndrome.

Human breast cancer and lymph node metastases express Gb3 and can be targeted by STxB-vectorized chemotherapeutic compounds

BACKGROUND

The B-subunit of Shiga toxin (STxB) specifically binds to the glycosphingolipid Gb3 that is highly expressed on a number of human tumors and has been shown to target tumor cells in mouse models and ex vivo on primary colon carcinoma specimen.

METHODS

Using a novel ex vivo STxB labeling (ESL) method we studied Gb3 expression in cytological specimens of primary human breast tumors from 107 patients, and in synchronous lymph node metastases from 20 patients. Fluorescent STxB was incubated with fine-needle aspiration (FNA) specimens, and Gb3 expression was evaluated by fluorescence microscopy. Furthermore, 11 patient-derived human breast cancer xenografts (HBCx) were evaluated for expression of Gb3 by ESL and FACS. In addition, the biodistribution of fluorescent STxB conjugate was studied after intravenous injection in a Gb3 positive HBCx model.

RESULTS

Gb3 expression was detected in 62 of 107 patients (57.9%), mainly in epithelial tumor cells. Gb3 positivity correlated with estrogen receptor expression (p≤0.01), whereas absence of Gb3 expression in primary tumors was correlated with the presence of lymph node metastases (p≤0.03). 65% of lymph node metastases were Gb3 positive and in 40% of tested patients, we observed a statistically significant increase of metastatic Gb3 expression (p≤0.04). Using concordant ESL and flow cytometry analysis, 6 out of 11 HBCx samples were scored positive. Intravenous injections of fluorescent STxB into HBC xenografted mice showed preferential STxB accumulation in epithelial cells and cells with endothelial morphology of the tumor.

CONCLUSION

The enhanced expression of Gb3 in primary breast carcinomas and its lymph node metastases indicate that the development of STxB-based therapeutic strategies is of interest in this pathology. Gb3 expressing HBCx can be used as a model for preclinical studies with STxB conjugates. Finally, the ESL technique on FNA represents a rapid and cost effective method for the stratification of patients in future clinical trials.

Vasculature analysis of patient derived tumor xenografts using species-specific PCR assays: evidence of tumor endothelial cells and atypical VEGFA-VEGFR1/2 signalings

BACKGROUND

Tumor endothelial transdifferentiation and VEGFR1/2 expression by cancer cells have been reported in glioblastoma but remain poorly documented for many other cancer types.

METHODS

To characterize vasculature of patient-derived tumor xenografts (PDXs), largely used in preclinical anti-angiogenic assays, we designed here species-specific real-time quantitative RT-PCR assays. Human and mouse PECAM1/CD31, ENG/CD105, FLT1/VEGFR1, KDR/VEGFR2 and VEGFA transcripts were analyzed in a large series of 150 PDXs established from 8 different tumor types (53 colorectal, 14 ovarian, 39 breast and 15 renal cell cancers, 6 small cell and 5 non small cell lung carcinomas, 13 cutaneous melanomas and 5 glioblastomas) and in two bevacizumab-treated non small cell lung carcinomas xenografts.

RESULTS

As expected, mouse cell proportion in PDXs -evaluated by quantifying expression of the housekeeping gene TBP- correlated with all mouse endothelial markers and human VEGFA RNA levels. More interestingly, we observed human PECAM1/CD31 and ENG/CD105 expression in all tumor types, with higher rate in glioblastoma and renal cancer xenografts. Human VEGFR expression profile varied widely depending on tumor types with particularly high levels of human FLT1/VEGFR1 transcripts in colon cancers and non small cell lung carcinomas, and upper levels of human KDR/VEGFR2 transcripts in non small cell lung carcinomas. Bevacizumab treatment induced significant low expression of mouse Pecam1/Cd31, Eng/Cd105, Flt1/Vegfr1 and Kdr/Vefr2 while the human PECAM1/CD31 and VEGFA were upregulated.

CONCLUSIONS

Taken together, our results strongly suggest existence of human tumor endothelial cells in all tumor types tested and of both stromal and tumoral autocrine VEGFA-VEGFR1/2 signalings. These findings should be considered when evaluating molecular mechanisms of preclinical response and resistance to tumor anti-angiogenic strategies.

Abstract P5-09-07: Identification of resistance-specific gene expression signatures in a breast cancer patient-derived xenograft with acquired resistance to different endocrine therapies

Background:

Acquired resistance to endocrine treatments (ET) occurs in more than 70% of cases of luminal breast cancer (LBC). We used patient derived xenografts (PDX) models of LBC to study molecular changes associated with acquired resistance to different ET modalities.

Methods:

A PDX model of LBC, established from an early stage BRCA2-mutated breast cancer, was treated with different ET (tamoxifen, fulvestrant, oophorectomy and letrozole) during several months. Tumors escaping to therapies were re-engrafted and maintained under therapy. ET-resistant and parental hormono-responders tumors were analyzed with immunohistochemistry (IHC), RT-PCR and Affymetrix Gene Expression Arrays. Hormono-resistant tumors were additionally studied for their in vivo response to ET, mTOR and PARP inhibitors.

Results:

From the initially ET sensitive HBCx22 xenograft model (Cottu, BCRT 2012) two resistant models were obtained respectively to tamoxifen (HBCx22-TamR) and to estrogen deprivation (HBCx22-OvaR). Unsupervised clustering of gene expression showed a clear cut separation between parental, TamR and OvaR tumors. Genes differentially expressed in TamR and OvaR tumors compared to parental HBCx22 were only partially overlapping. Up-Regulated genes in both TamR and OvaR tumors (n = 302) were involved in response to wounding, nucleotide metabolism, immune system, adhesion and cell growth. Biological Processes (BP) specifically deregulated in OvaR tumors (n = 380) included embryonic development, antigen presentation, amino acid and lipid metabolism. The top BP specifically regulated in TamR tumors (n = 1059) were response to estrogen and steroid hormones, TGF-b signaling, hypoxia, regulation of cell proliferation, with several strongly up-regulated genes of the histone clusters 1 and 3. Ingenuity Transcription Factor Analysis predicted activation of NFKB, SP1, AP-1 and JUN, and inhibition of ESR1. RT-PCR and IHC analyses confirmed the down regulation of ER controlled genes in the TamR tumors. Expression of ER co-regulators determined by RT-PCR showed that GREB1 was strongly reduced in TamR, while PBX1, GATA3 and FOXA1 were inhibited in OvaR. IHC analysis showed a loss of PTEN expression in HBCx22, with high levels of p-AKT and p-RPS6 in both parental and TamR and OvaR tumors. In vivo ET showed that the TamR xenograft was resistant to all modalities of ET, while OvaR was resistant to estrogen deprivation while retaining some sensitivity to tamoxifen and fulvestrant. Treatment with the mTOR inhibitor RAD001 arrested tumor growth but did not show any additive effect when combined to ET in TamR or OvaR tumors. Conversely, the combination of RAD001 with Olaparib was highly synergistic and induced complete tumor response in 70% of mice.

Conclusions:

According to the therapeutic selection, tumors derived from a PDX model of ER+ breast cancer show specific resistance patterns and gene expression profiles including disruption in the ER transcriptional program. The analysis of additional resistant tumors established from a second ER+ PDX will be presented at the meeting.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-09-07.

Abstract A9: Establishment and characterization of residual breast cancer patient-derived xenografts resistant to neo-adjuvant therapy

Background: In HER2 positive and triple-negative breast cancer subgroups, residual disease after neoadjuvant therapy is associated with higher risk of metastatic recurrence compared to patients achieving a pathological complete response. Residual tumor analysis after neoadjuvant treatment is a major and under-explored field to identify resistance mechanisms.

To develop patient-derived xenografts (PDX) of residual breast cancer we started a program of residual tumor engraftment in nude mice, following the same procedures previously published for PDX of human breast cancer (Marangoni et al, 2007 and Reyal et al, 2012).

Methods: 26 residual breast tumors and 2 residual metastatic axillary lymph nodes were engrafted in swiss nude mice immediately after surgery. Expression of Ki67, HER2, PTEN, P-AKT, P-S6, MET, RET and KIT were analyzed in xenografts by immunohistochemistry, western blot and RT-PCR analyses. Brain, lungs, liver and bones of xenografts were systematically formalin-fixed to search for human metastasis. The in vivo drug response of established xenografts was determined for the following treatments: adryamicin+cyclophosphamide (AC), docetaxel, capecitabine, cisplatin, irinotecan, everolimus, trastuzumab and lapatinib (for the HER2+ PDX). PDX tumors were additionally mechanically dissociated to establish cell lines.

Results: Seven PDX were established (tumor take of 25%), 5 triple-negative and 2 HER2+. Six out of seven PDX were metastatic in the lungs. Two xenografts were established from lymph node metastasis. The in vivo drug responses were concordant with the response to neo-adjuvant treatments in patients. Histological analyses showed that xenografts’ tumors recapitulated the patients’ tumor morphology. Residual tumor xenografts expressed high level of Ki67 protein and tumor latency during the first tumor passages was found to be shorter when compared to tumor latency of non pre-treated breast cancers. In 5/5 triple-negative breast cancer PDX the PTEN protein was lost and the PI3 kinase pathway activated. The mTOR inhibitor Everolimus was tested in 2 triple-negative PDX: one was resistant and one was responding, with a tumor growth inhibition of 80%. Triple-negative PDX show expression of “druggable” tyrosin kinase receptors (MET, RET, KIT) providing relevant models to test new target therapies in these models. One cell line was established from a highly metastatic triple-negative breast cancer xenograft. When re-injected into mice, the cell line was tumorigenic, however the tumor architecture was changed and the xenograft was not metastatic.

Conclusions: we have established a panel of metastatic PDX models of breast cancer resistant to neo-adjuvant therapies. These models provide a valuable preclinical tool to investigate mechanisms of resistance to neo-adjuvant treatments and for the preclinical testing of new targeted agents.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A9.

Citation Format: Elisabetta Marangoni, Dalila Labiod, Franck Assayag, Rania El Botty, Rana Hatem, Sophie Richon, Sophie Chateau-Joubert, Marine Carlus, Hélène Bonsang-Kitzis, Alice Pinheiro, Cécile Laurent, Ivan Bièche, Fabien Reyal. Establishment and characterization of residual breast cancer patient-derived xenografts resistant to neo-adjuvant therapy. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A9.

Abstract LB-34: Similar PI3K and RTK-Ras status in patient derived colorectal cancer-xenografts and patients

There is a recent increase in the use of patient-derived tumor xenografts (PDX) engrafted into immunodeficient mice as improved preclinical models of patient tumors. An important component in the validation of disease-specific PDXs for clinical relevance is comparing the genomic alterations and the response to standard agents. The CReMEC collection of 54 colorectal PDX has been recently reported to mimic the clinical situation for histopathological and molecular diversity of colorectal cancer. We further analyze here this colorectal PDX collection in regard to robust human patient molecular features: 1) Alterations in both PI3K and RTK-Ras pathways; 2) Role of oncogenic activation of EGFR-Ras downstream signaling on response to cetuximab.

The Cancer Genome Atlas Network (TCGA) newly reported a large genome-scale analysis of 276 colorectal cancer tissue samples, showing common genetic alterations in the PI3K and RTK-RAS pathways, with mutual exclusions in the PI3K pathway. The analysis of the PDX panel by CGH array, RNA expression (microarray, real-time qRT-PCR) and exome sequencing confirmed activation with mutual exclusion in PI3K pathway (IGF2 focal amplification/overexpression; IRS2 overexpression, mutation of PIK3CA, PIK3R1 and PTEN homozygous deletion). In RTK-Ras pathway, frequencies of genomic abnormalities (ERBB2 mutation/amplification; mutation of ERBB3, NRAS, KRAS and BRAF) in PDXs are fully in line with the TCGA patient collection.

The response to cetuximab of 52 subcutaneous engrafted PDX (including 24 KRAS mutated PDX) has been analyzed according to translated clinical criteria: xenograft regression as been defined as a partial response (decrease of at least 70% of the tumor volume measured at the beginning of the treatment) or as a complete response. In this unselected population, tumor regression occurred in 8 out of 52 cases (15%); all were KRAS wild type tumors. The percentage of responders was enriched up to 30% (7/23) when PTEN deletion and mutations of KRAS, BRAF, and PIK3CA are concomitantly excluded. These results completely fit with recent publication of data in patients treated with anti-EGFR antibodies.

Taken together, these results demonstrate that colorectal PDXs are representative clinical colorectal tumor models. They also underline their interest as appropriate tools to identify and test new targeted therapeutics.

Citation Format: Manoel Nunes, Louis-Bastien Weiswald, Patricia Vrignaud, Sophie Vacher, Edouard Turlotte, Sophie Richon, Dominique Bellet, Sergio Roman-Roman, Ivan Bieche, Virginie Dangles-Marie. Similar PI3K and RTK-Ras status in patient derived colorectal cancer-xenografts and patients. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-34. doi:10.1158/1538-7445.AM2013-LB-34

Abstract 85: Endocrine resistant luminal breast cancer xenografts are powerful models for the analysis of sensitivity to endocrine and everolimus treatments

Background. Activation of the PI3K pathway is associated with resistance to endocrine treatments (ET) in luminal breast cancer (LBC). Everolimus, an mTOR inhibitor, has been approved in combination with exemestane in endocrine resistant breast tumors. However, no definite signature of ET resistance or predictive factors of sensitivity to everolimus (EVE) treatment have been evidenced so far. In order to further decipher these molecular patterns, we used patient derived LBC xenografts (LBC-PDX) treated with various ET and EVE based combinations.

Methods. 3 LBC-PDX (named HBCx-3, HBCx-21 and HBCx-34) were treated with ET during several months to establish hormono-resistant (HR) xenografts. Both parental and HR models were treated by tamoxifen, estrogen deprivation, fulvestrant, EVE alone, and EVE combined with all three ET modalities. Tissue Micro Arrays from control and treated tumor samples were generated for IHC analyses. RT-PCR analyses were conducted on genes related to proliferation, ER, PI3K, IGF-1R and angiogenesis pathways.

Results. In primary PDX, ET showed a poor level of sensitivity for HBCx-3 and a high and sustained efficacy of ER targeting and/or ER deprivation for HBCx-21 and HBCx-34 tumors. In vivo resistance to ET was confirmed in all HR variants with tumor growth rates faster than parental xenografts. ER expression was conserved in HR tumors, but expression of the ER-responsive genes PS2, PR and MYB was strongly decreased, indicating impaired ER transcriptional activity. Acquired resistance to tamoxifen and ovariectomy was also associated to a strong decrease of IGF-1R signaling in HBCx-21, and was related to higher P-AKT expression, although P-pS6 was highly expressed in both sensitive and resistant tumors. Furthermore, in vivo experiments showed that EVE alone was highly efficient in all models independently of P-AKT expression/PTEN loss. EVE combined with fulvestrant yielded the most complete and durable tumor growth inhibition. In HBCx-3, proliferation and pS6 levels were markedly decreased only by the EVE-fulvestrant combination. In HBCx-21 and HBCx-34 HR models, EVE-based treatments decreased proliferation, expression of angiogenesis markers, as well as P-pS6 expression with no variation in (P-)AKT nor (P-)mTOR levels. A high IGF-1R protein expression was found only in the HBCx-34 TAM-R tumor, which was strongly decreased in the fulvestrant-treated tumors.

Conclusions. LBC-PDX with confirmed HR status have been established and may serve as models to study alternate therapies. Of note, in the HBCx-21 and -34 models, activation of the PI3K pathway is poorly correlated with baseline sensitivity to ET, suggesting other pathways of resistance. EVE alone is highly efficient in all settings, and combination with fulvestrant is promising at the in vivo and molecular levels. Proteomic, genomic and gene expression studies are ongoing.

Citation Format: Paul H. Cottu, Thomas Bagarre, Jean-Jacques Fontaine, Franck Assayag, Sophie Richon, Sophie Chateau-Joubert, Aurélie Thuleau, Patricia de Cremoux, Khemaies Slimane, Didier Decaudin, Anne Vincent-Salomon, Ivan Bièche, Elisabetta Marangoni. Endocrine resistant luminal breast cancer xenografts are powerful models for the analysis of sensitivity to endocrine and everolimus treatments . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 85. doi:10.1158/1538-7445.AM2013-85

Abstract LB-111: Mastospheres as a new 3D ex vivo breast cancer microtumors for preclinical drug testing

There is increasing evidence that three-dimensional (3D) tissue culture technologies have many uses within the preclinical assays in cancer. The 3D tumor model accurately reproduces the in vivo tumor phenotype and represents an additional tool for studying tumor biology and allowing better preclinical evaluation of anticancer drugs. One of the used models involves small tumor aggregates, termed spheres, that are obtained from mechanical tumor dissociation and that have shown the superiority of 3D culture over standard two-dimensional cell culture for mimicking the tumor biology and drug response observed in vivo. The aim of this study was to generate new ex vivo 3D models from breast (BC) cancer xenografts established from patients’ tumor fragments. These ex vivo mastospheres are easily obtained from mechanically dissociated fresh human BC tissue xenografted in Nude mice, in a similar way as colospheres from human colon cancer (Weiswald et al, Br J Cancer 2009, 101:473). In contrast to mammospheres described in the literature, 3D mastospheres are obtained from tumor fragments, without enzymatic tumor dissociation, without matrix substratum and in SVF supplemented medium. From a large panel of patient-derived BC xenografts already well characterized (Marangoni et al, Clin Cancer Res 2007, 13:3989; Cottu et al, Breast Cancer Res Treat 2011; Reyal et al, Breast Cancer Res 2012, 14:R11), we get mastospheres from 26 out of 36 (72%) xenografts. Mastosphere formation is scored on day 1 after culture according to the number of spheres/mg of dissociated xenograft tissue. Within mastospheres, we clearly distinguish 3 distinct morphologies: round, grape-like and aggregates. Histological analyses show also that mastospheres were formed only with proliferating cancer cells. In a reproducible way, dissociation of a given xenograft leads to a similar score and to a similar morphology. All BC subtypes (luminal, triple negative and HER2+ tumors) give rise to mastospheres. We noted that the 5 out of 5 xenografts (100%) able to metastasise in Nude mice (lung metastasis) form mastospheres, suggesting that the capacity to give mastospheres could be related to tumour aggressiveness, as already reported with colospheres and colon cancer. These different features prompted us to test the potential of these mastospheres in chemosensitivity assays. We first demonstrated that mastospheres can be kept viable a couple of days, consistent with ex vivo assay aim. For this purpose, we tested the sensitivity to cisplatin in two xenograft models with different in vivo response. We found that the paired mastospheres tested in viability assays mimicked these different response profiles (mean of IC50: 1.2 µM versus 15.5 µM). In conclusion, according to these preliminary data, mastospheres deserve additional investigation because of their interest as new ex vivo microtumour model.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-111. doi:1538-7445.AM2012-LB-111

In situ protein expression in tumour spheres: development of an immunostaining protocol for confocal microscopy

Background

Multicellular tumour sphere models have been shown to closely mimic phenotype characteristics of in vivo solid tumours, or to allow in vitro propagation of cancer stem cells (CSCs). CSCs are usually characterized by the expression of specific membrane markers using flow cytometry (FC) after enzymatic dissociation. Consequently, the spatial location of positive cells within spheres is not documented. Confocal microscopy is the best technique for the imaging of thick biological specimens after multi-labelling but suffers from poor antibody penetration. Thus, we describe here a new protocol for in situ confocal imaging of protein expression in intact spheroids.

Methods

Protein expression in whole spheroids (150 μm in diameter) from two human colon cancer cell lines, HT29 and CT320X6, has been investigated with confocal immunostaining, then compared with profiles obtained through paraffin immunohistochemistry (pIHC) and FC. Target antigens, relevant for colon cancer and with different expression patterns, have been studied.

Results

We first demonstrate that our procedure overcomes the well-known problem of antibody penetration in compact structures by performing immunostaining of EpCAM, a membrane protein expressed by all cells within our spheroids. EpCAM expression is detected in all cells, even the deepest ones. Likewise, antibody access is confirmed with CK20 and CD44 immunostaining. Confocal imaging shows that 100% of cells express β-catenin, mainly present in the plasma membrane with also cytoplasmic and nuclear staining, in agreement with FC and pIHC data. pIHC and confocal imaging show similar CA 19-9 cytoplasmic and membranar expression profile in a cell subpopulation. CA 19-9⁺ cell count confirms confocal imaging as a highly sensitive method (75%, 62% and 51%, for FC, confocal imaging and pIHC, respectively). Finally, confocal imaging reveals that the weak expression of CD133, a putative colon CSC marker, is restricted to the luminal cell surface of colorectal cancer acini, with CD133⁺ cellular debris into glandular lumina.

Conclusion

The present protocol enables in situ visualization of protein expression in compact three-dimensional models by whole mount confocal imaging, allowing the accurate localization and quantification of cells expressing specific markers. It should prove useful to study rare events like CSCs within tumour spheres.

Newly characterised ex vivo colospheres as a three-dimensional colon cancer cell model of tumour aggressiveness

Background:

New models continue to be required to improve our understanding of colorectal cancer progression. To this aim, we characterised in this study a three-dimensional multicellular tumour model that we named colospheres, directly obtained from mechanically dissociated colonic primary tumours and correlated with metastatic potential.

Methods:

Colorectal primary tumours (n=203) and 120 paired non-tumoral colon mucosa were mechanically disaggregated into small fragments for short-term cultures. Features of tumours producing colospheres were analysed. Further characterisation was performed using colospheres, generated from a human colon cancer xenograft, and spheroids, formed on agarose by the paired cancer cell lines.

Results:

Colospheres, exclusively formed by viable cancer cells, were obtained in only 1 day from 98 tumours (47%). Inversely, non-tumoral colonic mucosa never generated colospheres. Colosphere-forming capacity was statistically significantly associated with tumour aggressiveness, according to AJCC stage analysis. Despite a close morphology, colospheres displayed higher invasivity than did spheroids. Spheroids and colospheres migrated into Matrigel but matrix metalloproteinase (MMP)-2 and MMP-9 activity was detected only in colospheres. Mouse subrenal capsule assay revealed the unique tumorigenic and metastatic phenotype of colospheres. Moreover, colospheres and parental xenograft reproduced similar CD44 and CD133 expressions in which CD44⁺ cells represented a minority subset of the CD133⁺ population.

Conclusion:

The present colospheres provide an ex vivo three-dimensional model, potentially useful for studying metastatic process.

Changes in the maternal serum concentration of proearly placenta insulin-like growth factor peptides in normal vs abnormal pregnancy

OBJECTIVE

The objective of the study was to evaluate maternal serum pro-early placenta insulin like (proEPIL) levels during normal and pathologic pregnancy by using a newly developed enzyme-linked immunosorbent assay, based on a monoclonal antibody designated EPIL15 and directed to the pro-EPIL C-chain 98-108 region.

STUDY DESIGN

In a group of healthy pregnant women (n = 22), proEPIL peptide serum levels were measured longitudinally throughout gestation (8-12, 20-24, and 30-34 weeks). Serum proEPIL levels were measured in women with preterm labor (n = 24), intrauterine growth restriction (n = 27), and preeclampsia (n = 12).

RESULTS

In healthy pregnant women, a significant rise of serum pro-EPIL levels (mean +/- SEM) was observed during the third trimester of gestation (30.97 +/- 2.978 ng/mL; P < .01), with the highest serum levels at 30-34 weeks' gestation (P < .001). Serum proEPIL levels were found elevated in women with intrauterine growth restriction (107.4 +/- 12.99 ng/mL), preeclampsia (104.8 +/- 36.20 ng/mL), or preterm labor (183.8 +/- 36.42 ng/mL) in comparison with levels observed in healthy pregnant women (P < .001).

CONCLUSION

These results showed that proEPIL secretion increases in the last trimester during normal pregnancy and is highly secreted in women with pathologic conditions.

Isolation and characterization of spontaneous spheroid aggregates within human colon carcinomas

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Background: In vitro spheroid model using cancer cell lines is widely admitted to mimic in vivo micro tumors, including micrometastases. Floating spheroid cell cluster culture has been recently used for normal and cancer stem cell expansion. Spontaneously spheroids generated in vivo have been only studied in ovarian cancer ascites while organoid aggregates have been sometimes observed in the establishment of human colon cancer cell lines. In this study, we investigated whether spontaneous spheroid aggregates from colon cancer could be isolated and characterized. Methods: 127 colorectal primary tumor specimens have been collected and mechanically dissociated into small fragments, which were then shortly cultured on cell plastic flask. Production of spheroid- like structures, referred to as colospheres, was examined at Day 1 and colospheres were gathered for phenotypic characterization. Results: Colospheres were successfully generated from 67 surgical specimens (53%). The capacity to form colospheres was strictly restricted to tumor tissue: dissociated normal colon mucosa never generated colospheres and colospheres were formed exclusively by cancer cells. The ability to generate colospheres was demonstrated to be significantly related to tumor aggressiveness, according to nodal status and AJCC’s stages (Chi-2 test, p<0.05). Immunohistochemical studies showed that cells forming colospheres were frequently positive for Ki67, and displayed often a disturbed expression of the epithelial caretaker E-cadherin. Peripheral cells of colospheres were able to migrate into Matrigel in absence of any chemoattractant. Conclusions: Collectively, the morphology of these colospheres derived directly from tumoral tissues and made up exclusively of cancer cells, their potential capacity to acquire an epithelial-to-mesenchymal transition phenotype and their in vitro migration ability could be aligned with the collective migration properties of carcinomas. Consequently, these ex vivo spherical structures might form an in vitro cell system for micrometastasis studies, at the very time when mortality among colorectal cancer patients continues to be attributed to metastasis development.

No significant financial relationships to disclose.

Establishment of human colon cancer cell lines from fresh tumors versus xenografts: comparison of success rate and cell line features

Obtaining representative human colon cancer cell lines from fresh tumors is technically difficult. Using 32 tumor fragments from patients with colon cancer, the present study shows that prior xenograft leads to more efficient cell line establishment compared with direct establishment from fresh tumors (P < 0.05). From 26 tumor specimens, we successfully established 20 tumor xenografts in nude mice (77%); among 19 of these xenografts, 9 (47%) led to cell lines, including four from liver metastases. Only 3 of 31 tumor specimens (9.7%) grew immediately in vitro, and all were derived from primary tumors. To compare major phenotypic and genotypic characteristics of human colon cancer cell lines derived from the same tumor fragment using two protocols, the two pairs of cell lines obtained from 2 of 32 tumor fragments were extensively studied. They displayed similar morphology and were able to form compact spheroids. Chemosensitivity to 5-fluorouracil, CPT11, and L-OHP differed between cell lines obtained from patient tumors and those derived from xenografts. Matched cell lines shared a common core of karyotype alterations and distinctive additional chromosomal aberrations. Expression levels of genes selected for their role in oncogenesis evaluated by real-time quantitative PCR were found to be statistically correlated whatever the in vitro culture model used. In conclusion, xenotransplantation in mice of tumor fragments before establishment of cell lines enables generation of more novel human cancer cell lines for investigation of colon cancer cell biology, opening up the opportunity of reproducing the diversity of this disease.

Early placenta insuline-like peptide (pro-EPIL): A novel biomarker in advanced and metastatic non-small cell lung cancer (NSCLC) patients treated by chemotherapy

20069

Background: Some studies suggest a causal relationship between the early placenta insuline-like peptide encoded by the insulin-like 4 gene and cancer invasiveness. Methods: Serum concentrations of pro-EPIL were measured by ELISA using a novel two-site “sandwitch” assay, based on two monoclonal antibodies (mAb) raised against synthetic peptides analogous to two distinct regions of the pro-Epil polypeptide: mAb EPIL15, and biotinylated mAb EPIL02, used as the labelled indicator. The first mAb EPIL15 was purified and bound to a solid phase. Pro-EPIL was allowed to bind, and unbound proteins were removed by washing. The sensitivity limit of the assay was 3 ng/mL of synthetic peptide, and detection was linear over a range of at 3 pg to 200 ng of the synthetic peptide. As primary endpoint, we studied the Pro-EPIL distribution according to some clinico-biological prognostic factors. Results: Between July 2001 and April 2005, nineteen chemonaive NSCLC pts were treated by chemotherapy in our center and serum determinations of pro-EPIL were performed. Ten pts (63%) overexpressed pro-EPIL before start of chemotherapy with a median value of 1.06 ng/mL (range 0.01–6.75). Median age was 60 years (range 38–80), more than 90% of pts were men with an advanced or metastatic disease. Forty-two percent of pts had a large cell carcinoma subtype, with 25% of adenocarcinoma and 25% of epidermoid type. Immunologic evaluations were performed with a median value of the CD3+ lymphocites of 1290/mm3 (range 610–2138). Significant correlations were observed between age, serum alcaline phosphatase and CD3+ number. A border-line positive correlation was observed between pro-EPIL and CD3+ levels (P = 0.09, R2 = 0.5). Median OS for entire cohort was 7.5 months (95% CI, 5.5–9.4), with 67% deaths. Because our sample size was very low, no survival analysis were performed according to the baseline pro-EPIL value and other prognostic factors. A bootstrapping procedure is planned on our data. Conclusions: This results showed that pro-EPIL was overexpressed in the majority of advanced NSCLC pts. Interactions between this biomarker and immune system are possible. Furthemore, pro-EPIL as a therapeutic target might be tested in prospective studies.

No significant financial relationships to disclose.

Impairment of lymphocyte function in head-injured rats: effects of standard and immune-enhancing diets for enteral nutrition

BACKGROUND

The metabolic response to head injury (HI) is characterized by a dysimmunity which may be a risk factor of a septic state. The use of immune enhancing diets (IEDs) could be a promising approach to improve immune functions. The aim of the study was to investigate the consequences of HI on lymphocyte function and to determine the effects of an enteral IED comparatively to a standard enteral nutrition.

METHOD

A rat model of HI by fluid percussion was used. Twenty-five male Sprague-Dawley rats were randomized into 4 groups: rats receiving standard chow diet ad libitum (AL), rats sustaining HI and receiving standard chow diet and enteral saline (HI), rats receiving the enteral standard diet Sondalis HP (HIS), and rats receiving the IED Crucial (HIC). The two enteral diets were infused continuously during 4 days after the HI and were isocaloric, isonitrogenous and isovolumic.

RESULTS

HI induced a thymus atrophy (HI vs. AL, P<0.05), and an impairment in lymphocyte CD25 receptor density responsiveness to stimulation. The IED blunted thymus atrophy and allowed to preserve the stimulation of blood and Peyer patches lymphocytes (HIC: Stimulated vs. Basal, P<0.05).

CONCLUSION

IED seems more adapted for preserving lymphocyte function than standard diet in HI patients.

A three-dimensional tumor cell defect in activating autologous CTLs is associated with inefficient antigen presentation correlated with heat shock protein-70 down-regulation

We described previously a CTL clone able to lyse the autologous carcinoma cell line IGR-Heu after specific recognition of an HLA-A2/mutated alpha-actinin-4 peptide complex. Here, we used IGR-Heu, cultured either as standard two-dimensional monolayers or as three-dimensional spheroids, to further analyze the influence of target architecture on CTL reactivity. Interestingly, we found that changes in the tumor structure from two- to three-dimensional induced a dramatic decrease in its capacity to activate autologous CTL, as measured by IFN-gamma and tumor necrosis factor-alpha secretion. These functional alterations were attributable neither to MHC class I expression nor to tumor antigen (Ag) down-regulation, because IGR-Heu, cultured as two- or three-dimensional, expressed similar levels of HLA-A2 and alpha-actinin-4. More importantly, incubation of three-dimensional cells with synthetic epitope completely restored cytokine release by CTL. This defective Ag presentation correlated with a decrease in heat shock protein (hsp)70 expression by three-dimensional tumors compared with two-dimensional cells. Furthermore, transfection of the tumor cells with hsp70 cDNA completely restored the Ag-presenting potential of spheroids and, therefore, cytokine production by T cells. These data strongly suggest that hsp70 down-regulation in three-dimensional cells may result in tumor resistance to the immune response.

Gene expression profiles of bladder cancers: evidence for a striking effect of in vitro cell models on gene patterns

In order to assess the effect of in vitro models on the expression of key genes known to be implicated in the development or progression of cancer, we quantified by real-time quantitative PCR the expression of 28 key genes in three bladder cancer tissue specimens and in their derived cell lines, studied either as one-dimensional single cell suspensions, two-dimensional monolayers or three-dimensional spheroids. Global analysis of gene expression profiles showed that in vitro models had a dramatic impact upon gene expression. Remarkably, quantitative differences in gene expression of 2-63-fold were observed in 24 out of 28 genes among the cell models. In addition, we observed that the in vitro model which most closely mimicked in vivo mRNA phenotype varied with both the gene and the patient. These results provide evidence that mRNA expression databases based on cancer cell lines, which are studied to provide a rationale for selection of therapy on the basis of molecular characteristics of a patient's tumour, must be carefully interpreted.

Impact of human bladder cancer cell architecture on autologous T-lymphocyte activation

To investigate the influence of tumor cell architecture on T-cell activation, we used an autologous human model based on 2 bladder tumor cell lines as targets for cytotoxic tumor-infiltrating lymphocytes (TILs). These tumor cell lines were grown in vitro as either standard 2-dimensional (2D) monolayers or 3-dimensional (3D) spheroids. T-cell activation was determined by measuring the production of three major cytokines (tumor necrosis factor, granulocyte/macrophage colony-stimulating factor and interferon-gamma), known to be secreted by most activated TILs. Changes in the architecture of target cells from 2D to 3D induced a dramatic decrease in their capacity for stimulating TILs. Interestingly, neither TIL infiltration nor MHC class I, B7.1 costimulatory or lymphocyte function-associated factor-3 adhesion molecule downregulation played a major role in this decrease. These findings demonstrate that tumor architecture has a major impact on T-cell activation and might be implicated in the escape of tumor cells from the immune system.

Tumor-associated antigen human chorionic gonadotropin beta contains numerous antigenic determinants recognized by in vitro-induced CD8+ and CD4+ T lymphocytes

The beta subunit of human chorionic gonadotropin (hCG beta) is markedly overexpressed by neoplastic cells of differing histological origin including those present in colon, breast, prostate and bladder tumors. We have previously shown that some patients with hCG beta-producing urothelial tumors have circulating T cells that proliferate in response to hCG beta. To make a comprehensive study of hCG beta as a potential target for cancer immunotherapy, we investigated whether hCG beta peptides could induce CD4+ or CD8+ T-cell responses in vitro. By stimulating peripheral blood mononuclear cells (PBMCs) from three donors with mixtures of overlapping 16-mer synthetic peptides analogous to portions of either the hCG beta 20-71 or the hCG beta 102-129 region, we established six CD4+ T-cell lines that proliferated specifically in response to five distinct determinants located within these two hCG beta regions. Three antigenic determinants (hCG beta 52-67, 106-121 and 114-125) were presented by HLA-DR molecules, while the two other antigenic determinants (hCG beta 48-63 and 56-67) were presented by HLA-DQ molecules. Interestingly, one T-cell line specific for peptide hCG beta 106-121 recognized hCG beta peptides comprising, at position 117, either an alanine or an aspartic acid residue, with the latter residue being present within the protein expressed by some tumor cells. In addition, three other hCG beta-derived peptides that exhibited HLA-A*0201 binding ability were able to stimulate CD8+ cytotoxic T cells from two HLA-A*0201 donors. These three immunogenic peptides corresponded to regions hCG beta 40-48, hCG beta 44-52 and hCG beta 75-84. Our results indicate that the tumor-associated antigen hCG beta possesses numerous antigenic determinants liable to stimulate CD4+ and CD8+ T lymphocytes, and might thus be an effective target antigen for the immunotherapy of hCG beta-producing tumors.

MHC-dependent cytolysis of autologous tumor cells by lymphocytes infiltrating urothelial carcinomas

Tumor-infiltrating lymphocytes (TIL) were grown from 23 urothelial carcinomas. Phenotyping analysis showed that the TIL cultures were mainly CD3+. Although CD4+ and CD8+ T-cell sub-sets were grown in culture, CD4+ T-cell sub-sets predominated over CD8+ T cells. Immunohistochemical studies performed on 5 tumor specimens confirmed this observation, and indicated that CD4+ T cells surrounded the tumor islets, whereas CD8+ T lymphocytes were localized among the tumor cells. Five short-term carcinoma cell lines established from these urothelial tumors were used as target cells in cytolysis assays in order to investigate the functional anti-tumor activity of autologous TIL. TIL from 4/5 tumors were lytic and 3 TIL lines displayed MHC-class-I-dependent cytotoxicity directed against autologous tumor cells. CD4+ T-cell-depletion experiments performed on TIL line 07 confirmed that CD8+ MHC-class-I-dependent CTL were the predominant effectors. Finally, experiments performed on 6 allogeneic urothelial-cancer cell lines matched for HLA-class-I molecules showed that TIL07 exhibited selective lytic activity toward tumor 07. These data indicate that CD8+ MHC-class-I-dependent CTL present in urothelial carcinomas are functional and may participate in the anti-tumor immune response.