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.

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.

Modeling of response to endocrine therapy in a panel of human luminal breast cancer xenografts

Resistance to endocrine therapy is a major complication of luminal breast cancer and studies of the biological features of hormonal resistance are limited by the lack of adequate preclinical models. The aim of this study is to establish and characterize a panel of primary human luminal breast carcinoma xenografts, and to evaluate their response to endocrine therapies. Four hundred and twenty-three tumor fragments obtained directly from patients have been grafted in the interscapular fatpad of Swiss nude mice. After stable engraftment with estradiol supplementation, xenografted tumors have been validated by conventional pathology and immunohistochemistry examination, and additional molecular studies. In vivo tumor growth and response to different endocrine treatments were evaluated. We have engrafted 423 tumors including 314 ER+ tumors, and 8 new luminal breast cancer xenografts have been obtained (2.5%). Tumor take was much lower for luminal tumors than for non-luminal tumors (2.5 vs. 24.7%, P < 0.0001), and was associated with two independent criteria, i.e., ER status (P < 0.0001) and a high grade tumor (P = 0.05). Histological and immunohistochemical analyses performed on patient's tumors and xenografts showed striking similarities in the tumor morphology as well as in the expression level of ER, PR, and HER2. Response to hormone therapy, evaluated in 6 luminal models, showed different sensitivities, thus exhibiting heterogeneity similar to what is observed in the clinic. We have established a panel of primary human luminal breast cancer xenografts, recapitulating the biological and clinical behaviors of patient tumors, and therefore suitable for further preclinical experiments.

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.

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.

Molecular circuits shared by placental and cancer cells, and their implications in the proliferative, invasive and migratory capacities of trophoblasts

Trophoblast research over the past decades has underlined the striking similarities between the proliferative, migratory and invasive properties of placental cells and those of cancer cells. This review recapitulates the numerous key molecules, proto-oncogenes, growth factors, receptors, enzymes, hormones, peptides and tumour-associated antigens (TAAs) expressed by both trophoblastic and cancer cells in an attempt to evaluate the genes and proteins forming molecular circuits and regulating the similar behaviours of these cells. Among the autocrine and paracrine loops that might be involved in the strong proliferative capacity of trophoblastic and cancer cells, epidermal growth factor (EGF)/EGF receptor (EGFR), hepatocyte growth factor (HGF)/HGF receptor (HGFR) (Met) and vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) loops may play a predominant role. Similar mechanisms of migration and invasion displayed by trophoblastic and malignant cells comprise alterations in the adhesion molecule phenotype, including the increased expression of alpha1beta1 and alphavbeta3 integrin receptors, whereas another critical molecular event is the down-regulation of the cell adhesion molecule E-cadherin. Among proteases that may play an active role in the invasive capacities of these cells, accumulating evidence suggests that matrix metalloproteinase-9 (MMP-9) expression/activation is a prerequisite. Finally, an overview of molecular circuitries shared by trophoblast and cancer cells reveals that the activation of the phosphatidylinositol 3'-kinase (PI3K)/AKT axis has recently emerged as a central feature of signalling pathways used by these cells to achieve their proliferative, migratory and invasive processes.