Sensitivity of c-erbB positive cells to a ligand toxin and its utility in purging breast cancer cells from peripheral blood stem cell (PBSC) collections

Oncolytic viral purging of leukemic hematopoietic stem and progenitor cells with Myxoma virus

High-dose chemotherapy and radiation followed by autologous blood and marrow transplantation (ABMT) has been used for the treatment of certain cancers that are refractory to standard therapeutic regimes. However, a major challenge with ABMT for patients with hematologic malignancies is disease relapse, mainly due to either contamination with cancerous hematopoietic stem and progenitor cells (HSPCs) within the autograft or the persistence of residual therapy-resistant disease niches within the patient. Oncolytic viruses represent a promising therapeutic approach to prevent cancer relapse by eliminating tumor-initiating cells that contaminate the autograft. Here we summarize an ex vivo "purging" strategy with oncolytic Myxoma virus (MYXV) to remove cancer-initiating cells from patient autografts prior to transplantation. MYXV, a novel oncolytic poxvirus with potent anti-cancer properties in a variety of in vivo tumor models, can specifically eliminate cancerous stem and progenitor cells from samples obtained from acute myelogenous leukemia (AML) patients, while sparing normal CD34+ hematopoietic stem and progenitor cells capable of rescuing hematopoiesis following high dose conditioning. We propose that a broader subset of patients with intractable hematologic malignancies who have failed standard therapy could become eligible for ABMT when the treatment schema is coupled with ex vivo oncolytic therapy.

Downregulation of HER2/neu receptor by solamargine enhances anticancer drug-mediated cytotoxicity in breast cancer cells with high-expressing HER2/neu

Overexpression of HER2/neu is associated with drug resistance and poor outcome in breast cancer. Solamargine (SM), a glycoalkaloid purified from the herb Solanum incanum, exhibits HER2/neu gene modulation of HER2/neu high-expressing human breast cancer cell line ZR-75-1. SM downregulation of HER2/neu gene expression was determined by RT-PCR and Southern hybridization. Additionally, the membrane-bound HER2/neu receptor in highly HER2/neu-expressing breast cancer cells was determined by radioimmunoassay, immunocytochemistry, fluorescent immunocytochemistry, and flow cytometry. SM significantly decreased the number of HER2/neu receptors on the cell membrane. Methotrexate (MTX), 5-florouracil (5-Fu), and cisplatin (CDDP) are commonly used for breast carcinoma treatment in clinics; however, patients with HER2/neu overexpression exhibit resistance to these anticancer drugs. Notably, combination of MTX, 5-Fu, and CDDP with SM individually increased the susceptibility of breast cancer cells to these chemotherapeutic agents. Experimental results indicated that downregulation of HER2/neu by SM might be an effective strategy for enhancing drug susceptibility of breast cancer cells expressing high levels of HER2/neu.

Isolation and development of haematopoietic progenitor cells from peripheral blood of adult and newborn pigs

Pluripotent stem cells (PSCs), already described in human beings, are fibroblast-like cells that exhibit a CD34 marker specific for haematopoietic stem cells. In this work we have demonstrated the presence of PSCs in the peripheral blood of pigs, a species frequently used in transplantation studies as an animal model for human diseases. Differentiation into haematopoietic colonies (granulomacrophagic colonies, erythroid colonies and mixed colonies) has been carried out with the peripheral blood of adult and newborn pigs, using solely human commercial media. Peripheral blood mononuclear cells (PBMNCs) were cultured in semisolid methylcellulose based media enriched with recombinant human cytokines, achieving granulomacrophagic-colony forming unit (GM-CFU) and mixed-colony forming unit (Mix-CFU) growth with erythroblastic lineage proliferation in the presence of erythropoietin (Epo). In all the samples CFU growth was associated with the presence of recombinant human cytokine. No evidence of proliferation in control plates without cytokines was found. From liquid medium culture, a population of macrophages and CD34+ fibroblast like cells were retrieved 21 days after sowing. These findings allow us to think about the direct application of this simple and standardised method in several work fields such as the study of pharmacological effects of many drugs over the haematopoietic line and in the study of new strategies in cellular therapy for some human diseases.

Viral purging of haematological autografts: should we sneeze on the graft?

High-dose cytotoxic chemotherapy followed by autologous haematopoietic stem cell transplantation (ASCT) is extensively used for the treatment of many haematopoietic, as well as several epithelial cancers. Disease relapse may be the result of tumour contamination within autograft as evidenced by gene marking studies. The multiple purging strategies that have been described to date have not proven effective in most ASCT settings. This review addresses the possibility of using oncolytic viruses as a novel purging strategy. DNA viruses such as genetically engineered adenoviral vectors have widely been used to deliver either a prodrug-activating enzyme or express wild-type p53 selectively in tumour cells in ex vivo purging protocols. In addition, conditionally replicating adenoviruses that selectively replicate in tumour cells and herpes simplex virus type 1 are other DNA viruses that have been tested as ex vivo purging agents under laboratory conditions. Vesicular stomatitis virus (VSV) and reovirus are naturally occurring RNA viruses that appear to hold promise as purging agents under ex vivo and in vivo settings. Preclinical data demonstrate reovirus's purging potential against breast, monocytic and myeloma cell lines as well as patient-derived tumours of diffuse large B-cell lymphoma, chronic lymphocytic leukaemia, Waldenstrom macroglobulinemia and small lymphocytic lymphoma. In addition, VSV has shown effective killing of leukaemic cell lines and multiple myeloma patient specimens. Given the increasing interest in the utilization of viruses as purging agents, the following review provides a timely summary of the potential and the challenges of oncolytic viruses as purging modalities during ASCT.

Study and culture of haematopoietic progenitor cells from peripheral blood in rats, hamsters and mice

The aim of this work was to isolate and cultivate a subpopulation of pluripotent stem cells present in peripheral blood of different animal species, frequently used in laboratory studies (mice, rats and hamsters). Pluripotent stem cells (PSCs), already described in human beings, are fibroblast-like cells that exhibit a CD34 marker, specific for haematopoietic stem cells. Commonly used human commercial media were investigated for culturing animal PSCs. These findings suggest that this simple and standardized methodology may be applicable in several fields such as the study of the pharmacological effects of drugs on the haematopoietic line and the study of new strategies in cellular therapy for some human diseases.

Biological purging of breast cancer cell lines using a replication-competent oncolytic virus in human stem cell autografts

Autologous hematological stem cell transplantation (ASCT) is used for the treatment of many hematological and several solid cancers. ASCT, however, has proven disappointing as a therapeutic strategy for breast cancer. Our group and others have previously shown that breast cancer micrometastases found in patients' apheresis products (APs) predict shorter progression-free and overall survival. The implications of this finding are twofold: (i) contaminating tumor cells (CTCs) in AP reflect a higher systemic disease burden and/or (ii) reinfused CTCs contribute to relapse/progressive disease. To date, purging strategies have been disappointing. We have previously demonstrated the oncolytic properties of reovirus in in vitro, in vivo and ex vivo systems. In the present study, we tested the hypothesis that reovirus purges CTCs in a breast cancer cell line purging model. Reovirus-infected human breast cancer cell lines (HTB 133, HTB 132, SKBR3 and MCF7) exhibited cell death within days. Admixtures of AP with cells from breast tumor cell lines, which were then exposed to reovirus, showed complete purging of CTCs (assessed via flow cytometry/tumor cell outgrowth analysis) without deleterious effect on CD34+ cells. Our results provide preclinical support for the ex vivo use of reovirus as a purging modality for breast cancer during ASCT.

Reovirus oncolysis as a novel purging strategy for autologous stem cell transplantation

Hematologic stem cell rescue after high-dose cytotoxic therapy is extensively used for the treatment of many hematopoietic and solid cancers. Gene marking studies suggest that occult tumor cells within the autograft may contribute to clinical relapse. To date purging of autografts contaminated with cancer cells has been unsuccessful. The selective oncolytic property of reovirus against myriad malignant histologies in in vitro, in vivo, and ex vivo systems has been previously demonstrated. In the present study we have shown that reovirus can successfully purge cancer cells within autografts. Human monocytic and myeloma cell lines as well as enriched ex vivo lymphoma, myeloma, and Waldenström macroglobulinemia patient tumor specimens were used in an experimental purging model. Viability of the cell lines or purified ex vivo tumor cells of diffuse large B-cell lymphoma, chronic lymphocytic leukemia, Waldenström macroglobulinemia, and small lymphocytic lymphoma was significantly reduced after reovirus treatment. Further, [35S]-methionine labeling and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of cellular proteins demonstrated reovirus protein synthesis and disruption of host cell protein synthesis as early as 24 hours. Admixtures of apheresis product with the abovementioned tumor cells and cell lines treated with reovirus showed complete purging of disease. In contrast, reovirus purging of enriched ex vivo multiple myeloma, Burkitt lymphoma, and follicular lymphoma was incomplete. The oncolytic action of reovirus did not affect CD34+ stem cells or their long-term colony-forming assays even after granulocyte colony-stimulating factor (G-CSF) stimulation. Our results indicate the ex vivo use of an unattenuated oncolytic virus as an attractive purging strategy for autologous stem cell transplantations.

A deletion mutant of heregulin increases the sensitivity of breast cancer cells to chemotherapy without promoting tumorigenicity

Heregulin (HRG) is an activator of the erbB2-, erbB3- and erbB4-(erbB-2/3/4) signaling pathway. Transfection of full-length HRG cDNA into the estrogen (E2)-dependent cell line MCF-7 promoted an invasive E2-independent phenotype, as well as persistent activation of the erbB-2/3/4 receptors. Moreover, HRG expression in MCF-7 cells renders the cells sensitive to the topoisomerase II inhibitor doxorubicin (Doxo). In an attempt to dissociate the tumorigenic effect of HRG from the sensitizing effect to chemotherapy, we constructed a structural deletion mutant of HRG. Transfection of the deletion mutant of HRG described in this study (HRG/M) into MCF-7 cells resulted in the dissociation of the tumor-promoting activity of HRG from the sensitization to Doxo, that is, although the cells did not become more aggressive or E2-independent they became more sensitive to Doxo. HRG/M was unable to autophosphorylate the erbB receptors and did not affect the level of MAPK phosphorylation. Furthermore, the intracellular localization of the protein was different from that of the full-length protein. Our data show that the HRG/M sequences are sufficient to sensitize MCF-7 cells to Doxo, and provide evidence that this sensitization is independent of erbB2 activation.

HER/erbB receptors as therapeutic targets of immunotoxins in human rhabdomyosarcoma cells

Human rhabdomyosarcoma cells express HER/erbB growth factors receptors. Receptors belonging to this family are overexpressed and play a role in many types of epithelial and neural cancer and have been selected as targets for cancer therapy. In this paper EGF-R, HER-2 and HER-3 receptors were tested as therapeutic targets of immunotoxins in human rhabdomyosarcoma. Rhabdomyosarcoma cells were treated with indirect immunotoxins consisting in primary specific murine monoclonal antibodies recognizing EGF-R, HER-2 and HER-3 followed by secondary F(ab')2 antimouse immunoglobulin linked to saporin-S6, a type 1 ribosome-inactivating protein (RIP) from the seeds of Saponaria officinalis. The indirect immunotoxin targeting EGF-R caused a significant inhibition in cell growth and protein synthesis and a strong increase in apoptosis in rhabdomyosarcoma cells, whereas indirect immunotoxins against HER-2 and HER-3 were ineffective. The toxic activity of anti-EGF-R immunotoxin was also observed on rhabdomyosarcoma cells expressing low level of EGF-R. EGF-R could be a novel therapeutic target of immunotoxins in human rhabdomyosarcoma.