CENP-A Subnuclear Localization Pattern as Marker Predicting Curability by Chemoradiation Therapy for Locally Advanced Head and Neck Cancer Patients

Simple Summary

For clinicians, rapid diagnosis of early neoplastic lesions and prediction of treatment response are two key aspects to guide their choice of treatment. Current histological markers are based on proliferation, differentiation states or specific cell function, but do not take full advantage of tumor characteristics. We show that the subnuclear distribution of CENP-A, the centromeric histone variant, provides, for both aspects, information distinct from and independent of commonly used markers. Our study reveals that in locally advanced head and neck squamous cell cancer patients, the subnuclear distribution of CENP-A at the time of diagnosis is an independent predictive marker of local disease control and curability by concurrent chemoradiation therapy. We provide evidence for the clinical applicability of this CENP-A labeling as a cost-effective marker regardless of genetic alterations in the tumor, perfectly compatible with the clinical time constraints in the course of therapy.

Abstract

Effective biomarkers predictive of the response to treatments are key for precision medicine. This study identifies the staining pattern of the centromeric histone 3 variant, CENP-A, as a predictive biomarker of locoregional disease curability by chemoradiation therapy. We compared by imaging the subnuclear distribution of CENP-A in normal and tumoral tissues, and in a retrospective study in biopsies of 62 locally advanced head and neck squamous cell carcinoma (HNSCC) patients treated by chemoradiation therapy. We looked for predictive factors of locoregional disease control and patient’s survival, including CENP-A patterns, Ki67, HPV status and anisokaryosis. In different normal tissues, we reproducibly found a CENP-A subnuclear pattern characterized by CENP-A clusters both localized at the nuclear periphery and regularly spaced. In corresponding tumors, both features are lost. In locally advanced HNSCC, a specific CENP-A pattern identified in pretreatment biopsies predicts definitive locoregional disease control after chemoradiation treatment in 96% (24/25) of patients (OR = 17.6 CI 95% [2.6; 362.8], p = 0.002), independently of anisokaryosis, Ki67 labeling or HPV status. The characteristics of the subnuclear pattern of CENP-A in cell nuclei revealed by immunohistochemistry could provide an easy to use a reliable marker of disease curability by chemoradiation therapy in locally advanced HNSCC patients.

A Potential Renewed Use of Very Heavy Ions for Therapy: Neon Minibeam Radiation Therapy

Simple Summary

The treatment of hypoxic tumours continues to be one of the main challenges for radiation therapy. Minibeam radiation therapy (MBRT) shows a highly promising reduction of to-xicity in normal tissue, so that very heavy ions, such as Neon (Ne) or Argon (Ar), with extremely high LET, might become applicable to clinical situations. The high LET in the target would be unrivalled to overcome hypoxia, while MBRT might limit the side effects normally preventing the use of those heavy ions in a conventional radiotherapeutic setting. The work reported in this manuscript is the first experimental proof of the remarkable reduction of normal tissue (skin) toxicities after Ne MBRT irradiations as compared to conventional Ne irradiations. This result might allow for a renewed use of very heavy ions for cancer therapy.

Abstract

(1) Background: among all types of radiation, very heavy ions, such as Neon (Ne) or Argon (Ar), are the optimum candidates for hypoxic tumor treatments due to their reduced oxygen enhancement effect. However, their pioneering clinical use in the 1970s was halted due to severe side effects. The aim of this work was to provide a first proof that the combination of very heavy ions with minibeam radiation therapy leads to a minimization of toxicities and, thus, opening the door for a renewed use of heavy ions for therapy; (2) Methods: mouse legs were irradiated with either Ne MBRT or Ne broad beams at the same average dose. Skin toxicity was scored for a period of four weeks. Histopathology evaluations were carried out at the end of the study; (3) Results: a significant difference in toxicity was observed between the two irradiated groups. While severe da-mage, including necrosis, was observed in the broad beam group, only light to mild erythema was present in the MBRT group; (4) Conclusion: Ne MBRT is significantly better tolerated than conventional broad beam irradiations.

Spatially Modulated Proton Minibeams Results in the Same Increase of Lifespan as a Uniform Target Dose Coverage in F98-Glioma-Bearing Rats

Proton minibeam radiation therapy (pMBRT) is a new approach in proton radiotherapy, by which a significant increase in the therapeutic index has already been demonstrated in RG2 glioma-bearing rats. In the current study we investigated the response of other types of glioma (F98) and performed a comparative evaluation of tumor control effectiveness by pMBRT (with different levels of dose heterogeneity) versus conventional proton therapy. The results of our study showed an equivalent increase in the lifespan for all evaluated groups (conventional proton irradiation and pMBRT) and no significant differences in the histopathological analysis of the tumors or remaining brain tissue. The reduced long-term toxicity observed with pMBRT in previous evaluations at the same dose suggests a possible use of pMBRT to treat glioma with less side effects while ensuring the same tumor control achieved with standard proton therapy.

X-rays minibeam radiation therapy at a conventional irradiator: Pilot evaluation in F98-glioma bearing rats and dose calculations in a human phantom

Minibeam radiation therapy (MBRT) is a type of spatial fractionated radiotherapy that uses submillimetric beams. This work reports on a pilot study on normal tissue response and the increase of the lifespan of glioma-bearing rats when irradiated with a tabletop x-ray system. Our results show a significant widening of the therapeutic window for brain tumours treated with MBRT: an important proportion of long-term survivals (60%) coupled with a significant reduction of toxicity when compared with conventional (broad beam) irradiations. In addition, the clinical translation of the minibeam treatment at a conventional irradiator is evaluated through a possible human head treatment plan.

Short and long-term evaluation of the impact of proton minibeam radiation therapy on motor, emotional and cognitive functions

Radiotherapy (RT) is one of the most frequently used methods for cancer treatment. Despite remarkable advancements in RT techniquesthe treatment of radioresistant tumours (i.e. high-grade gliomas) is not yet satisfactory. Finding novel approaches less damaging for normal tissues is of utmost importance. This would make it possible to increase the dose applied to tumours, resulting in an improvement in the cure rate. Along this line, proton minibeam radiation therapy (pMBRT) is a novel strategy that allows the spatial modulation of the dose, leading to minimal damage to brain structures compared to a high dose (25 Gy in one fraction) of standard proton therapy (PT). The aim of the present study was to evaluate whether pMBRT also preserves important cerebral functions. Comprehensive longitudinal behavioural studies were performed in irradiated (peak dose of 57 Gy in one fraction) and control rats to evaluate the impact of pMBRT on motor function (motor coordination, muscular tonus, and locomotor activity), emotional function (anxiety, fear, motivation, and impulsivity), and cognitive function (learning, memory, temporal processing, and decision making). The evaluations, which were conducted over a period of 10 months, showed no significant motor or emotional dysfunction in pMBRT-irradiated rats compared with control animals. Concerning cognitive functions, similar performance was observed between the groups, although some slight learning delays might be present in some of the tests in the long term after irradiation. This study shows the minimal impact of pMBRT on the normal brain at the functional level.

ZRANB2 and SYF2-mediated splicing programs converging on ECT2 are involved in breast cancer cell resistance to doxorubicin

Besides analyses of specific alternative splicing (AS) variants, little is known about AS regulatory pathways and programs involved in anticancer drug resistance. Doxorubicin is widely used in breast cancer chemotherapy. Here, we identified 1723 AS events and 41 splicing factors regulated in a breast cancer cell model of acquired resistance to doxorubicin. An RNAi screen on splicing factors identified the little studied ZRANB2 and SYF2, whose depletion partially reversed doxorubicin resistance. By RNAi and RNA-seq in resistant cells, we found that the AS programs controlled by ZRANB2 and SYF2 were enriched in resistance-associated AS events, and converged on the ECT2 splice variant including exon 5 (ECT2-Ex5+). Both ZRANB2 and SYF2 were found associated with ECT2 pre-messenger RNA, and ECT2-Ex5+ isoform depletion reduced doxorubicin resistance. Following doxorubicin treatment, resistant cells accumulated in S phase, which partially depended on ZRANB2, SYF2 and the ECT2-Ex5+ isoform. Finally, doxorubicin combination with an oligonucleotide inhibiting ECT2-Ex5 inclusion reduced doxorubicin-resistant tumor growth in mouse xenografts, and high ECT2-Ex5 inclusion levels were associated with bad prognosis in breast cancer treated with chemotherapy. Altogether, our data identify AS programs controlled by ZRANB2 and SYF2 and converging on ECT2, that participate to breast cancer cell resistance to doxorubicin.

Tumor Control in RG2 Glioma-Bearing Rats: A Comparison Between Proton Minibeam Therapy and Standard Proton Therapy

PURPOSE

Proton minibeam radiation therapy (pMBRT) is a novel radiation therapy approach that exploits the synergies of proton therapy with the gain in normal tissue preservation observed upon irradiation with narrow, spatially fractionated, beams. The net gain in normal tissue sparing that has been shown by pMBRT may lead to the efficient treatment of very radioresistant tumors, which are currently mostly treated palliatively. The aim of this study was to perform an evaluation of the tumor effectiveness of proton minibeam radiation therapy for the treatment of RG2 glioma-bearing rats.

METHODS AND MATERIALS

Two groups (n = 9) of RG2 glioma-bearing rats were irradiated with either standard proton therapy or with pMBRT, with a dose prescription of 25 Gy in 1 fraction. The animals were followed up for a maximum of 6 months. At the end of the study, histopathological studies were performed to assess both the tumor presence and the possible side effects.

RESULTS

Tumor control was achieved in the 2 irradiated series, with superior survival in the pMBRT group compared with the standard proton therapy group. Long-term (>170 days) survival rates of 22% and 67% were obtained in the standard proton therapy and pMBRT groups, respectively. No tumor was observed in the histopathological analysis. Although animals with long-term survival in the standard radiation therapy exhibit substantial brain damage, including marked radionecrosis, less severe toxicity was observed in the pMBRT group.

CONCLUSIONS

pMBRT offers a significant increase in the therapeutic index of brain tumors: The majority of the glioma-bearing rats (67%) survived 6 months with less severe side effects.

Primary CNS lymphoma patient-derived orthotopic xenograft model capture the biological and molecular characteristics of the disease

Primary CNS lymphomas (PCNSL) are rare and poor prognosis diffuse large B-cell lymphomas. Because of the brain tumor environment and the restricted distribution of drugs in the CNS, specific PCNSL patient-derived orthotopic xenograft (PDOX) models are needed for preclinical research to improve the prognosis of PCNSL patients. PCNSL patient specimens (n = 6) were grafted in the caudate nucleus of immunodeficient nude mice with a 83% rate of success, while subcutaneous implantation in nude mice of human PCNSL sample did not generate lymphoma, supporting the role of the brain microenvironment in the PCNSL physiopathology. PDOXs showed diffuse infiltration of B-cell lymphoma cells in the brain parenchyma. Each model had a unique mutational signature for genes in the BCR and NF-κB pathways and retained the mutational profile of the primary tumor. The models can be stored as cryopreserved biobank. Human IL-10 levels measured in the plasma of PCNSL-PDOX mice showed to be a reliable tool to monitor the tumor burden. Treatment response could be measured after a short treatment with the targeted therapy ibrutinib. In summary, we established a panel of human PCNSL-PDOX models that capture the histological and molecular characteristics of the disease and that proved suitable for preclinical experiments. Our methods of generation and characterization will enable the generation of additional PDOX-PCNSL models, essential tools for cognitive and preclinical drug discovery.

Proton minibeam radiation therapy widens the therapeutic index for high-grade gliomas

Proton minibeam radiation therapy (pMBRT) is a novel strategy which has already shown a remarkable reduction in neurotoxicity as to compared with standard proton therapy. Here we report on the first evaluation of tumor control effectiveness in glioma bearing rats with highly spatially modulated proton beams. Whole brains (excluding the olfactory bulb) of Fischer 344 rats were irradiated. Four groups of animals were considered: a control group (RG2 tumor bearing rats), a second group of RG2 tumor-bearing rats and a third group of normal rats that received pMBRT (70 Gy peak dose in one fraction) with very heterogeneous dose distributions, and a control group of normal rats. The tumor-bearing and normal animals were followed-up for 6 months and one year, respectively. pMBRT leads to a significant tumor control and tumor eradication in 22% of the cases. No substantial brain damage which confirms the widening of the therapeutic window for high-grade gliomas offered by pMBRT. Additionally, the fact that large areas of the brain can be irradiated with pMBRT without significant side effects, would allow facing the infiltrative nature of gliomas.

Transfer of Minibeam Radiation Therapy into a cost-effective equipment for radiobiological studies: a proof of concept

Minibeam radiation therapy (MBRT) is an innovative synchrotron radiotherapy technique able to shift the normal tissue complication probability curves to significantly higher doses. However, its exploration was hindered due to the limited and expensive beamtime at synchrotrons. The aim of this work was to develop a cost-effective equipment to perform systematic radiobiological studies in view of MBRT. Tumor control for various tumor entities will be addressable as well as studies to unravel the distinct biological mechanisms involved in normal and tumor tissues responses when applying MBRT. With that aim, a series of modifications of a small animal irradiator were performed to make it suitable for MBRT experiments. In addition, the brains of two groups of rats were irradiated. Half of the animals received a standard irradiation, the other half, MBRT. The animals were followed-up for 6.5 months. Substantial brain damage was observed in the group receiving standard RT, in contrast to the MBRT group, where no significant lesions were observed. This work proves the feasibility of the transfer of MBRT outside synchrotron sources towards a small animal irradiator.

Proton minibeam radiation therapy spares normal rat brain: Long-Term Clinical, Radiological and Histopathological Analysis

Proton minibeam radiation therapy (pMBRT) is a novel strategy for minimizing normal tissue damage resulting from radiotherapy treatments. This strategy partners the inherent advantages of protons for radiotherapy with the gain in normal tissue preservation observed upon irradiation with narrow, spatially fractionated beams. In this study, whole brains (excluding the olfactory bulb) of Fischer 344 rats (n = 16) were irradiated at the Orsay Proton Therapy Center. Half of the animals received standard proton irradiation, while the other half were irradiated with pMBRT at the same average dose (25 Gy in one fraction). The animals were followed-up for 6 months. A magnetic resonance imaging (MRI) study using a 7-T small-animal MRI scanner was performed along with a histological analysis. Rats treated with conventional proton irradiation exhibited severe moist desquamation, permanent epilation and substantial brain damage. In contrast, rats in the pMBRT group exhibited no skin damage, reversible epilation and significantly reduced brain damage; some brain damage was observed in only one out of the eight irradiated rats. These results demonstrate that pMBRT leads to an increase in normal tissue resistance. This net gain in normal tissue sparing can lead to the efficient treatment of very radio-resistant tumours, which are currently mostly treated palliatively.

Abstract 1687: Vandetanib as a potential new treatment for ER negative breast cancers

Introduction: Recent studies have shown that the receptor tyrosine kinase RET is involved in the biology of ER positive breast cancers and in the response to endocrine treatment, but its role in ER negative tumors is unknown. Here we investigated the expression of RET in BC patients tumors and patient-derived xenografts (PDX) and evaluated the therapeutic potential of Vandetanib in ER negative BC PDX.

Methods: RET mRNA expression was analyzed in BC of 446 patients and 57 PDX by RT-PCR analysis. The activity of Vandetanib, a tyrosine kinase inhibitor targeting RET, EGFR and VEGFR2, was tested in three PDX of triple-negative breast cancer (TNBC) and one PDX of HER2+ BC with different levels of RET expression. Protein expression of P-RET, RET, EGFR, P-EGFR and c-KIT were determined by immunohistochemistry (IHC). Analyses of PI3K and MAPK pathways and angiogenesis were performed by IHC and RT-PCR in both untreated and Vandetanib-treated tumors.

Results: In both clinical samples and PDX, elevated levels of RET were found in ER+ and HER2+ tumors, and in a subgroup of TNBC tumors. In the HBCx5 (HER2+) and HBCx24 (TNBC) PDX, both with RET over-expression, treatment by Vandetanib resulted in tumor growth inhibition (TGI) of 90% and 98%, respectively. In both models, tumor regressions were observed in 50% of xenografts. The effect of Vandetanib was associated to a marked inhibition of RET phosphorylation. To determine whether the lack of RET over-expression was associate to Vandetanib resistance, we treated two additional TNBC PDX with low and no expression of RET: HBCx4B and HBCx14. In these models, treatment by Vandetanib still inhibited tumor growth with a TGI of 85%. Tumor regressions were registered in 42% of animals in the PDX model with low expression of RET (HBCx4B), while no tumor regression were observed in HBCx14. IHC analyses showed an over-expression of EGFR in the HBCx4B xenograft and inhibition of EGFR phosphorylation in treated tumors, suggesting that tumor response to Vandetanib could depend on EGFR inhibition in this tumor. Further analyses of treated tumors revealed a decreased expression of phospho-ERK in the 4 PDX models, indicating inhibition of MAPK pathway, while the phosphorylation status of the PI3K pathway markers S6 and 4EBP1 was unchanged. Finally, treatment by Vandetanib decreased expression of murine Vegf receptors and the endothelial marker Cd31 in the 4 PDX tested, indicating angiogenesis inhibition.

Conclusions: Treatment by Vandetanib resulted in strong tumor growth inhibition in ER negative PDX with over-expression of RET. This effect was associated to inhibition of RET phosphorylation and MAPK pathway and decreased tumor vascularization. The lack of RET over-expression did not predict Vandetanib resistance, and over-expression of EGFR was also associated to a marked tumor response. These preclinical results suggest that Vandetanib treatment could be useful for patients with ER negative breast cancers expressing Vandetanib's targets.

Citation Format: Elisabetta Marangoni, Rana Hatem, Dalila Labiod, Sophie Chateau-Joubert, Rania El Botty, Jean-Luc Servely, Ludmilla De Plater, Ivan Bièche. Vandetanib as a potential new treatment for ER negative breast cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1687. doi:10.1158/1538-7445.AM2015-1687

Abstract 4499: Activation of PI3-kinase pathway and tumor response to everolimus in patient-derived xenografts of triple-negative breast cancer

Purpose: Patients with triple-negative breast cancer (TNBC) have a poor prognosis and targeted therapies are lacking. Recent studies performed on patients tumors showed and increased activity of the phosphatidylinositol 3-kinase (PI3K) pathway in TNBC. PI3K pathway is critical for cell growth, survival, and angiogenesis. Everolimus is a mTOR inhibitor recently showed to increase survival of patients with metastatic luminal breast cancer. The objectives of this work were to analyze the PI3K activation status in a large cohort of patient-derived xenografts (PDX) of TNBC and to investigate the therapeutic potential of mTOR inhibition.

Experimental procedures: this study included a panel of 32 TNBC PDX models previously described (Marangoni et al 2007). Expression of AKT, P-AKT, P-mTOR, S6, P-S6, P-4EBP1, PTEN and INPP4B was analyzed by WB and IHC. Mutations of PIK3CA (exons 9 and 20), PIK3R1 (exons 11-15), and AKT1 (exon 4) were detected by sequencing of cDNA fragments obtained by RT-PCR amplification. The efficacy of the mTOR inhibitor everolimus was investigated in vivo on 10 PDX models with different expressions and mutational status of PI3K markers.

Results: INPP4B protein expression was lost in 56% of tumors (n=18) and expressed at low levels in 31% of models, while only 2 models displayed a marked expression. PTEN expression was lost in 78% of tumors. Thirteen PDX models (40%) displayed a concomitant loss of both INPP4B and PTEN proteins. In 67% of tumors, the ratio between phosphorylated and unphosphorylated AKT was greater than 1. S6 was found to be phosphorylated in the great majority of tumors. PI3KCA and AKT1 genes were mutated only in 1 and 2 tumors, respectively. On the 10 PDX models treated with everolimus, 6 models responded to treatment with a tumor growth inhibition (TGI) comprised between 60% and 80%. Four models were classified as resistant or low responder (TGI<50%). Preliminary analysis of treated tumors from 6 models indicates increased level of P-AKT (feedback loop) to occur only in responder models, while inhibition of S6 phosphorylation occurred in treated tumors from both responder and resistant models. Finally, expression of INPP4B or PTEN alone did not predict for tumor response, while a P-AKT/AKT ratio greater than 1 predicted response to everolimus (p<0.05, Fisher's exact test).

Conclusions: the majority of TNBC PDX models showed loss of PTEN or INPP4B proteins or both, associated with activation of PI3K pathway. Preliminary results obtained from 10 PDX models indicate that mTOR targeting resulted in tumor growth inhibition in several models with AKT phosphorylation. Additional TNBC models will be tested in order to search for robust predictive biomarkers. This large panel of characterized PDX of TNBC models represents a clinical relevant tool to investigate the activity of PI3K-AKT-mTOR inhibitors and identify predictive biomarkers.

Citation Format: Elisabetta Marangoni, Rana Hatem, Rania El Botty, Ludmilla De Plater, Dalila Labiod, Sophie Vacher, Sophie Chateau-Joubert, Ivan Bièche. Activation of PI3-kinase pathway and tumor response to everolimus in patient-derived xenografts of triple-negative breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4499. doi:10.1158/1538-7445.AM2014-4499

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-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

Abstract A15: Establishment and characterization of a new patient-derived non-small cell lung cancer xenograft panel for pharmacological assessment

Background: Development of targeted therapies in non-small cell lung carcinoma (NSCLC) is rapidly growing and offers promising treatment perspectives for cancer patients. However, the assessment of new therapeutic compounds requires preclinical models defined by precise tumor molecular features that could impact their antitumor efficacy. The aim of this study was then to develop and characterize a new reliable panel of human NSCLC xenografts.

Material and methods: From 28 samples of NSCLC specimens obtained from patient's surgery and grafted into Swiss nude mice, 18 transplantable xenografts were established (64%). Molecular characterization included histological features, gene mutation status (EGFR, KRAS, and BRAF), and research of ALK translocation in both xenografts and their corresponding patient's tumors. For determination of the predictive value of the models, a standard pharmacological assessment was then performed in 6 adenocarcinoma (ADK) models using the EGFR inhibitor erlotinib (50 mg/kg/day, 5 days/week, 4 weeks, orally). Tumor Growth Inhibition (TGI) was calculated to measure the efficiency of erlotinib. Finally, to evaluate responses to erlotinib according to individual mouse variability, we decided to consider each mouse as one tumor-bearing entity. In all in vivo experiments, a relative tumor volume variation (RTVV) of each erlotinib-treated mouse was calculated from the following formula: Vt/Vc, where Vt is the volume of the treated mouse and Vc the median volume of the corresponding control group at a time corresponding to the end of treatment. An overall response rate (ORR) was then calculated for both EGFR-mutated and -non mutated tumors.

Results: Among the 18 established models, we have diagnosed 9 ADK, 6 epidermoid carcinomas, and 3 undifferientiated large cell cancers, with a high degree of similarity with the originated patient's tumors in regard to histological characteristics (Morphology and IHC), and a complete concordance for gene mutation status. Among the 18 NSCLC xenografts, 3 were EGFR mutated (exon 18 G719A, exon 19 del18b, and exon 21 L858R) and 3 others were KRAS mutated (G12C). No BRAF mutation nor ALK translocation were found. Erlotinib induced a TGI of 30%, 62%, and 93% for the 3 EGFR-mutated xenografts, and 0% (preliminary result), 37%, and 52% (KRAS-mutated model) for the 3 wild type EGFR tumors. Moreover, the individual mouse ORR ORR ≥ 90% was 26% in the first group and 4% in the second one, respectively (p < 0,05).

Conclusions: We have developed and characterized a new panel of primary human NSCLC xenografts that is highly representative of the heterogeneity of the disease and responses to the anti-EGFR targeted therapy, and provides precious tools to assess innovative therapeutic approaches.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A15.