Engraftment of MDR1 and NeoR Gene-Transduced Hematopoietic Cells After Breast Cancer Chemotherapy

Abstract

To determine whether the multidrug resistance gene MDR1could act as a selectable marker in human subjects, we studied engraftment of peripheral blood progenitor cells (PBPCs) transduced with either MDR1 or the bacterial NeoR gene in six breast cancer patients. This study differed from previous MDR1 gene therapy studies in that patients received only PBPCs incubated in retroviral supernatants (no nonmanipulated PBPCs were infused), transduction of PBPCs was supported with autologous bone marrow stroma without additional cytokines, and a control gene (NeoR) was used for comparison with MDR1. Transduced PBPCs were infused after high-dose alkylating agent therapy and before chemotherapy with MDR-substrate drugs. We found that hematopoietic reconstitution can occur using only PBPCs incubated ex vivo, that theMDR1 gene product may play a role in engraftment, and that chemotherapy may selectively expand MDR1 gene-transduced hematopoietic cells relative to NeoR transduced cells in some patients.

Genetic protection of repopulating hematopoietic cells with an improved MDR1‐retrovirus allows administration of intensified chemotherapy following stem cell transplantation in mice

“…It remains to be determined to what extent differences in vector design, multiplicity of infection and other conditions related to the experimental protocol might be responsible for this disparity. In accordance with our data and those from clinical trials and nonhuman primates, [17][18][19][20][21][22]47 transgenic mice that expressed MDR1 in BM cells also did not present with signs of myeloproliferation or myelodysplasia, 11 indicating that there may be a therapeutic win-790 dow for MDR1 overexpression in genetically engineered hematopoietic cells.…”

“…48,49 Therefore, it is tempting to speculate that some clinical trials with MDR1 vectors may have failed because of the delay and/or insufficient stem cell toxicity in administering chemotherapy following transplantation of genemodified cells. [17][18][19]22,23 Since our study indicates that improved MDR1 vectors promise a successful chemoprotection of repopulating hematopoietic cells, it seems plausible to continue with careful clinical evaluation of this approach.…”

“…Despite early success with establishing proof of principle that protection from myelotoxic side effects of systemic chemotherapy might be possible with retroviral gene transfer of MDR1 in mice, [12][13][14][15][16] no studies have been published that provide convincing evidence that transgenic MDR1 will protect from severe hematopoietic side effects in a novel chemotherapeutic concept of potential clinical value. Several clinical trials performed to evaluate the safety and efficiency of retroviral MDR1-gene transfer in human hematopoietic cells were compromised by insufficient expression of MDR1 from retroviral vectors [17][18][19][20][21][22] or by low gene transfer efficiency (with the notable exception of reference 20).…”

Progress with retroviral gene vectors

“…In tumour therapy, retrovirus vectors have mainly been applied ex vivo to transduce immunomodulatory molecules (e.g. IL-2 and IFN-c) into neoplastic cells (autologous tumour cell vaccines) [88,89] and tumour in®ltrating lymphocytes [90] or to transduce the multidrug resistance gene into autologous bone marrow cells in order to induce higher tolerance to chemotherapy agents [91,92]. Treatment of brain tumours represents the most frequent in vivo application of retroviral vectors.…”

Reversal of Multidrug Resistance with LY335979: Functional Analysis of P-glycoprotein-Mediated Transport Activity and Its Modulation In Vivo

“…Several high-potency modulators are now in clinical trials. [9][10][11][12][13][14] Second, transgenic expression of the MDR1 gene has been explored for hematopoietic cell protection in the context of cancer chemotherapy, [15][16][17][18][19] wherein Pgp could protect hematopoietic progenitor cells from chemotherapy-induced myelosupression. For proper use of MDR modulators as well as monitoring MDR gene therapy in chemotherapeutic protocols, identification of transporter-mediated resistance could guide the choice of agents and provide important prognostic information for cancer patients.…”