Retroviral Gene Transfer in Autologous Bone Marrow Transplantation for Adult Acute Leukemia

Abstract

To evaluate whether marrow contributes to relapse after autologous bone marrow transplantation (AuBMT) for acute leukemia, transplanted marrow was marked with the G1N retroviral vector (Genetic Therapy Inc.) containing the neomycin phosphotransferase gene (neo). Between April 1992 and August 1993, 4 patients were transplanted for acute myeloid leukemia (AML) in second complete remission (CR) and 1 patient for acute lymphoid leukemia in first CR. An average of 12.4% (range 5-19%) of transplanted marrow mononuclear cells were exposed to G1N vector for 4 hr. In the vector-treated portion of the marrow, 4.9% of GM-CFU and 3.6% of erythroid burst-forming units (BFU-E) were resistant to G418 in vitro. In the 5 patients, the polymerase chain reaction (PCR) detected the neo sequence on only two occasions after AuBMT. Of 4 patients surviving 1 year after transplantation, only 1 had evidence of gene marked cells by PCR. Two AML patients have relapsed, one of whom had evidence of neo sequences in the bone marrow at day 100 but not at relapse 11 months after AuBMT. The second patient relapsed 18 months after AuBMT but never had PCR evidence of neo sequences before or after relapse. Our results indicate vector-transduced autologous bone marrow from heavily pretreated adults with acute leukemia mark with low efficiency, although vector sequences have been detected in bone marrow and peripheral blood up to 1 year after transplant. Of the 2 relapsed patients, no evidence of vector-marked leukemic blasts have been detected.

Stroma-conditioned medium and sufficient prestimulation improve fibronectin fragment-mediated retroviral gene transfer into human primitive mobilized peripheral blood stem cells through effects on their recovery and transduction efficiency

“…[30][31][32] This dramatic loss of individual stem cell quality after ex vivo culture of HSC could explain the disappointing results of the clinical gene transfer studies. 2,[6][7][8][9] In our view, CAFC week 6 after ex vivo manipulation do not only produce less LTC-CFC in vitro but may also have reduced in vivo repopulating capacity. Therefore, future clinical gene therapy studies should not only assess the number of genetically transduced stem cells but also their individual repopulating quality.…”

“…[3][4][5] The most desirable approach in human gene therapy trials is a cell-free virus-containing supernatant transduction protocol, but clinical trials using this supernatant approach have demonstrated low levels of gene delivery to repopulating HSC. 2,[6][7][8][9] Although mobilized PBSC are clinically the most relevant target cells for cancer gene therapy in adult patients, these cells are likely to be resistant to stable integration of transduced genes. It has been shown that primitive HSC from mobilized peripheral blood are quiescent [10][11][12][13] and refractory to cell cycle activation.…”

No Discrepancy between in Vivo Gene Marking Efficiency Assessed in Peripheral Blood Populations Compared with Bone Marrow Progenitors or CD34+ Cells

“…In the canine autologous transplantation model one investigator noted a similar discrepancy between the overall level of marking in marrow mononuclear cells and in CFU-GMs (Carter et al, 1992). However, other human clinical trials using similar or identical retroviral vectors have not detected this phenomenon Cornetta et al, 1996;Emmons et al, 1997). These observations have not been investigated systematically, with concurrent samples of peripheral blood cells, CFU-Cs or purified CD34 1 cells obtained for analysis from the same individuals over time.…”

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“…However, one should bear in mind that this does not rule out the possibility that residual disease in the patients investigated also played a role in the relapses that took place. Similar types of trials have been performed in acute lymphocytic leukemia, myeloma, breast cancer, lymphoma and chronic lymphocytic lymphoma but so far no neo marked relapses have been reported (13)(14)(15)(16). Since in most of these studies the transduction efficiency has been low, these negative findings do not exclude that unmarked cells in the harvests have contributed to the disease reoccurrence in these trials as well.…”

“…Since in most of these studies the transduction efficiency has been low, these negative findings do not exclude that unmarked cells in the harvests have contributed to the disease reoccurrence in these trials as well. In one trial only 10% of the harvest was actually exposed to the vector, further reducing the chance of finding marked cells at relapse (16).…”