A Novel Targeted Therapeutic Approach to Multiple Myeloma Using Tumor Specific Anti-Sense RNA Sequences

Despite recent advances in the therapy of multiple myeloma (MM), the disease remains incurable. Current drugs for MM target not only MM but also normal cells. This limits the efficacy of these agents and may lead to significant morbidities for patients. Therefore, novel strategies are needed that allow targeting of tumor cells in these patients without affecting nonmalignant cells. MM is a malignancy of clonal antibody-secreting plasma cells with specific rearrangement of DNA that is transcribed into a unique mRNA sequence that is translated into the tumor specific monoclonal antibody. These tumor specific transcripts are abundant in all of the malignant cells of these patients. We have explored the possibility of using a unique sequence from this transcript, the complementarity determining region (CDR) gene sequence, to direct drug release into MM cells. Using a quenched fluorescein-labeled oligonucleotide sequence complementary to the CDR3 gene sequence from the MM cell line RPMI8226 as a probe, our results have demonstrated that quenched fluorescent signals of this RPMI8226-specific oligonucleotide were released upon binding to the CDR3 gene sequence of RPMI8226, but not to oligo(dT), random sequences or the CDR3 gene sequence from another MM cell line, U266. Similarly, using a quenched fluorescein-labeled oligonucleotide sequence complementary to the CDR3 gene sequence from U266 as a probe, our results have also shown that quenched fluorescent signals of the U266-specific oligonucleotide were released upon binding to the CDR3 gene sequence of U266, but not to oligo(dT), random sequences or the CDR3 gene sequence from RPMI8226. In addition, transfection of 8226- or U266-specific oligonucleotides into 8226 and U266 cells indicated that the oligonucleotides specifically discriminated the two cell lines. Furthermore, these oligonucleotides are stable in PBS or in transfected cells for at least 48hrs at 37°C, long enough for killing of MM cells with most currently available anti-MM drugs. Currently, we are evaluating the efficacy of this targeted approach to specifically identify tumor cells, and developing therapeutic modification of the oligonucleotide to allow drug delivery specifically to the tumor cells. Our studies validate a new strategy for MM treatment that may introduce a new targeted therapeutic approach in MM as well as other B cell malignancy, without impacting nonmalignant cells, which should allow much higher concentrations of drugs to be delivered into the tumor cells. Updated results using this novel targeted treatment approach will be reported at the meeting.