Fariba Nemati

Characterization of a Large Panel of Patient-Derived Tumor Xenografts Representing the Clinical Heterogeneity of Human Colorectal Cancer

Purpose: Patient-derived xenograft models are considered to represent the heterogeneity of human cancers and advanced preclinical models. Our consortium joins efforts to extensively develop and characterize a new collection of patient-derived colorectal cancer (CRC) models. Experimental Design: From the 85 unsupervised surgical colorectal samples collection, 54 tumors were successfully xenografted in immunodeficient mice and rats, representing 35 primary tumors, 5 peritoneal carcinoses and 14 metastases. Histologic and molecular characterization of patient tumors, first and late passages on mice includes the sequence of key genes involved in CRC (i.e., APC, KRAS, TP53), aCGH, and transcriptomic analysis. Results: This comprehensive characterization shows that our collection recapitulates the clinical situation about the histopathology and molecular diversity of CRC. Moreover, patient tumors and corresponding models are clustering together allowing comparison studies between clinical and preclinical data. Hence, we conducted pharmacologic monotherapy studies with standard of care for CRC (5-fluorouracil, oxaliplatin, irinotecan, and cetuximab). Through this extensive in vivo analysis, we have shown the loss of human stroma cells after engraftment, observed a metastatic phenotype in some models, and finally compared the molecular profile with the drug sensitivity of each tumor model. Through an experimental cetuximab phase II trial, we confirmed the key role of KRAS mutation in cetuximab resistance. Conclusions: This new collection could bring benefit to evaluate novel targeted therapeutic strategies and to better understand the basis for sensitivity or resistance of tumors from individual patients. Clin Cancer Res; 18(19); 5314–28. ©2012 AACR.

Ability of Doxorubicin-Loaded Nanoparticles to Overcome Multidrug Resistance of Tumor Cells After Their Capture by Macrophages

AbstractPurpose. Investigation of the ability of doxorubicin-loaded nanoparticles (NP/Dox) to overcome multidrug resistance (MDR) when they have first been taken up by macrophages. Methods. The growth inhibition of P388 sensitive (P388) and resistant (P388/ADR) tumor cells was evaluated in a coculture system consisting of wells with two compartments. The tumor cells were seeded into the lower compartment, the macrophages were introduced into the upper part in which the drug preparations were also added. Results. Doxorubicin exerted lower cytotoxicity on tumor cells in coculture compared with direct contact. In P388/ADR, NP/Dox cytotoxicity was far higher than that of free doxorubicin (Dox). Three different formulations of cyclosporin A (either free (CyA), loaded to nanoparticles (NP/CyA) or in a combined formulation with doxorubicin (NP/Dox-CyA)), were added to modulate doxorubicin efficacy. The addition of cyclosporin A to Dox increased drug cytotoxicity. Both CyA added to NP/Dox and NP/Dox-CyA were able to bypass drug resistance. Conclusions. Despite the barrier role of macrophages, NP/Dox remained far more cytotoxic than Dox against P388/ADR. Both NP/ Dox + CyA and NP/Dox-CyA allowed to overcome MDR, but the last one should present greater advantagein vivo by confining both drugs in the same compartment, hence reducing the adverse effects.

Polo-like Kinase 1: A Potential Therapeutic Option in Combination with Conventional Chemotherapy for the Management of Patients with Triple-Negative Breast Cancer

Breast cancers are composed of molecularly distinct subtypes with different clinical outcomes and responses to therapy. To discover potential therapeutic targets for the poor prognosis-associated triple-negative breast cancer (TNBC), gene expression profiling was carried out on a cohort of 130 breast cancer samples. Polo-like kinase 1 (PLK1) was found to be significantly overexpressed in TNBC compared with the other breast cancer subtypes. High PLK1 expression was confirmed by reverse phase protein and tissue microarrays. In triple-negative cell lines, RNAi-mediated PLK1 depletion or inhibition of PLK1 activity with a small molecule (BI-2536) induced an increase in phosphorylated H2AX, G(2)-M arrest, and apoptosis. A soft-agar colony assay showed that PLK1 silencing impaired clonogenic potential of TNBC cell lines. When cells were grown in extracellular matrix gels (Matrigel), and exposed to BI-2536, apoptosis was observed specifically in TNBC cancerous cells, and not in a normal cell line. When administrated as a single agent, the PLK1 inhibitor significantly impaired tumor growth in vivo in two xenografts models established from biopsies of patients with TNBC. Most importantly, the administration of BI-2536, in combination with doxorubicin + cyclophosphamide chemotherapy, led to a faster complete response compared with the chemotherapy treatment alone and prevented relapse, which is the major risk associated with TNBC. Altogether, our observations suggest PLK1 inhibition as an attractive therapeutic approach, in association with conventional chemotherapy, for the management of patients with TNBC.

Clinical and experimental progression of a new model of human prostate cancer and therapeutic approach.

We report the clinical evolution of a prostate cancer, metastasizing to lungs and bones, recurring locally, and escaping from anti-androgen therapy. Key event of biological progression of the patients tumor was the coincidence of allelic imbalance accumulation and of bone metastases occurrence. The recurrent tumor was established as the transplantable xenograft PAC120 in nude mice, where it grew locally. PAC120 displayed the same immunophenotype of the original tumor (positive for keratin, vimentin, prostatic acid phosphatase, and Leu-7) and expressed human HOXB9, HOXA4, HER-2/neu, and prostate-specific antigen genes, as detected by reverse transcriptase-polymerase chain reaction. It formed lung micrometastases detected by mRNA expression of human genes. Cytogenetic analysis demonstrated numerous alterations reflecting the tumor evolution. PAC120 was still hormone-dependent; its growth was strongly inhibited by the new gonadotropin-releasing hormone antagonist FE 200486 but weakly by gonadotropin-releasing hormone superagonist D-Trp(6)-luteinizing-hormone releasing hormone (decapeptyl). Tumor growth inhibition induced by anti-hormone therapy was linked to the hormone deprivation degree, more important and more stable with FE 200486 than with D-Trp(6)-luteinizing-hormone releasing hormone. Surgical castration of mice led to tumor regressions but did not prevent late recurrences. Transition to hormone-independent tumors was frequently associated with a mucoid differentiation or with a neuroendocrine-like pattern. Independent variations of mRNA expression of HER-2/neu and prostate-specific antigen were observed in hormone-independent tumors whereas HOXB9 gene expression was constant. In conclusion, PAC120 xenograft, a new model of hormone-dependent prostate cancer retained the progression potential of the original tumor, opening the opportunity to study the hormone dependence escape mechanism.

Pyrophosphorolysis-activated polymerization detects circulating tumor DNA in metastatic uveal melanoma.

Purpose: To develop a molecular tool to detect circulating tumor–derived DNA (ctDNA) in the plasma from patients with uveal melanoma as a marker of tumor burden and monitor treatment efficacy. Experimental Design: A real-time PCR was developed on the basis of bidirectional pyrophosphorolysis-activated polymerization (bi-PAP) for the quantification of ctDNA using 3′blocked primer pairs specific for the 3 recurrent mutually exclusive mutations of Gα subunits GNAQ and GNA11. Results: Sensitivity and specificity of bi-PAP were assessed on serial dilutions of tumor DNA in normal DNA for the 3 recurrent mutations. Each assay could detect a single mutated molecule per reaction, whereas 104 copies of normal DNA were not detected. The ctDNA was readily detected in plasma of mice bearing uveal melanoma xenografts in amounts proportional to circulating human DNA. Finally, plasma was almost always found positive (20 of 21 tested patients) in a prospective analysis of patients with metastatic uveal melanoma. Conclusions: Bi-PAP assays detect and quantify ctDNA in patients with metastatic uveal melanoma. A prospective study is ongoing to assess the clinical usefulness of ctDNA level in uveal melanoma. Clin Cancer Res; 18(14); 3934–41. ©2012 AACR.

In vivo efficacy of STI571 in xenografted human small cell lung cancer alone or combined with chemotherapy.

STI571, or imatinib, selectively inhibits BCR/ABL, PDGFR and c‐kit kinase activity. It has been reported that a large proportion of small cell lung cancer (SCLC) cell lines and tumors express c‐kit and that STI571 inhibits tumor cell growth. We therefore investigated the therapeutic efficacy of STI571, alone or combined with chemotherapy, in human SCLC cells or tumors xenografted into nude mice. The level of c‐kit mRNA expression was variable in SCLC tumors (positive for 2 of 4 xenografts), and c‐kit protein was not detected by immunohistochemistry. On the 4 xenografted tumors, PDGFRα and PDGFRβ were not detected by immunohistochemistry. STI571 induced inhibition of proliferation of the SCLC6 cell line without inducing apoptosis; in contrast, in combination with etoposide or topotecan, the growth inhibition of SCLC6 cells induced by STI571 was increased, with apoptotic DNA fragmentation. Four human SCLC xenografts (SCLC6, SCLC61, SCLC74 and SCLC108) were transplanted into mice. After intraperitoneal injection of STI571, we observed 80%, 40% and 78% growth inhibition of SCLC6, SCLC61 and SCLC108 tumors, respectively, without any significant inhibition of SCLC74 tumor growth. In mice bearing responsive SCLC tumors, we observed an increase of growth inhibition induced by chemotherapy (etoposide + ifosfamide or topotecan) by concomitant and continuous administration of STI571, associated with an increase of toxic deaths. In SCLC6‐bearing mice receiving sequential treatments, we observed a reduction of toxic deaths but a decrease of synergistic antitumor efficacy. In conclusion, the efficacy of STI571 alone in SCLC xenografted tumors was variable and did not depend on c‐kit expression. Moreover, a significant increase of chemotherapy‐induced growth inhibition was obtained by concomitant administration of STI571 that should be carefully investigated in SCLC patients.

Patient-derived xenografts recapitulate molecular features of human uveal melanomas.

We have previously developed a new method for the development and maintenance of uveal melanoma (UM) xenografts in immunodeficient mice. Here, we compare the genetic profiles of the primary tumors to their corresponding xenografts that have been passaged over time. The study included sixteen primary UMs and corresponding xenografts at very early (P1), early (P4), and late (P9) in vivo passages. The tumors were analyzed for mutation status of GNAQ, GNA11, GNAS, GNA15, BAP1, and BRAF, chromosomal copy number alterations using Affymetrix GeneChip® Genome‐Wide Human SNP6.0 arrays, gene expression profiles using GeneChip® Human Exon 1.0 ST arrays, BAP1 mRNA and protein expression, and MAPK pathway status using Reverse Phase Protein Arrays (RPPA). The UM xenografts accurately recapitulated the genetic features of primary human UMs and they exhibited genetic stability over the course of their in vivo maintenance. Our technique for establishing and maintaining primary UMs as xenograft tumors in immunodeficient mice exhibit a high degree of genetic conservation between the primary tumors and the xenograft tumors over multiple passages in vivo. These models therefore constitute valuable preclinical tool for drug screening in UM.

Clinical relevance of human cancer xenografts as a tool for preclinical assessment: example of in-vivo evaluation of topotecan-based chemotherapy in a panel of human small-cell lung cancer xenografts

Prediction of human tumor response based on preclinical data could reduce the failure rates of subsequent new anticancer drugs clinical development. Human small-cell lung carcinomas (SCLC) are characterized by high initial sensitivity to chemotherapy but a low median survival time because of drug resistance. The aim of this study was to evaluate the therapeutic relevance of a panel of human SCLC xenografts established in our laboratory using one compromising drug in SCLC, topotecan (TPT). Six SCLC xenografts derived from six patients were used: three were sensitive to a combination of etoposide (VP16), cisplatin (CDDP), and ifosfamide (IFO), and three were resistant, as published earlier. Growth inhibition was greater than 84% for five xenografts at doses of 1–2 mg/kg/day. TPT was combined with IFO, etoposide (VP16), and CDDP. IFO improved the efficacy of TPT in three of the five xenografts and complete responses were obtained even with the less TPT-sensitive xenograft. VP16 increased the efficacy of two of four xenografts and complete responses were obtained. The combination of TPT and CDDP did not improve TPT responses for any of the xenografts tested. Semiquantitative reverse transcriptase-PCR of genes involved in drug response, such as topoisomerase I, topoisomerase II&agr;, multidrug resistance 1 (MDR1), multidrug resistance-associated protein (MRP), lung resistance-related protein (LRP), and glutathione S-transferase π (GSTπ), did not explain the variability in drug sensitivity between SCLC xenografts. In conclusion, these preclinical data mirror those from published clinical studies suggesting that our panel of SCLC xenografts represents a useful tool for preclinical assessment of new treatments.

Conjunctival low-grade non-Hodgkin's lymphoma: a large single-center study of initial characteristics, natural history and prognostic factors

To define the initial characteristics and prognostic factors of patients with conjunctival low-grade malignant lymphoma, all patients treated for low-grade lymphoma with initial conjunctival involvement were reviewed. Forty-nine cases were selected, including 45 cases with exclusive ophthalmologic conjunctival involvement. Pathologic review showed 55% of mucosa-associated lymphoid tissue type lymphoma, and 23% of lymphoplasmocytic lymphoma. Initial characteristics were median age of 62 years, nodal involvement in 17% of cases, and stage IV in 22% of patients with 10% of bone marrow involvement. With a median follow-up of 75 months, the 5-year disease-free survival (DFS) and overall survival were 65% and 83%, respectively. On multivariate analysis, nodal involvement was the only factor with a pejorative impact on DFS. Our patient cohort represents one of the largest published series defining the characteristics and prognostic factors of primary conjunctival low-grade malignant lymphoma.

In Vivo Tumor Targeting by the B-Subunit of Shiga Toxin

Delivery of drugs to the appropriate target cells would improve efficacy and reduce potential side effects. The nontoxic B-subunit of the intestinal pathogen-produced Shiga toxin (STxB) binds specifically to the glycosphingolipid Gb3, overex-pressed in membranes of certain tumor cells, and enters these cells through the retrograde pathway. Therefore, STxB binding to Gb3 receptors may be useful for cell-specific vectorization or imaging purposes. Here we labeled STxB with a fluorophore to evaluate its potential as an in vivo cell-specific targeting reagent in two different models of human colorectal carcinoma. Fluorescent STxB was administered systemically to xenografted nude mice, and its biodistribution was studied by optical imaging. The use of fluorescent STxB allowed the combination of the macroscopic observations with analyses at the cellular level using confocal microscopy. After administration, the fluorescent STxB was slowly eliminated by renal excretion. However, it accumulated in the tumor area. Furthermore, STxB was demonstrated to enter the Gb3-expressing tumoral cells, as well as the epithelial cells of the neovascularization and the monocytes and macrophages surrounding the xenografts.