Researchers from the University of Illinois Urbana-Champaign have developed a groundbreaking approach to target and eliminate leukemia stem cells (LSCs) using drug-delivering DNA aptamers, potentially addressing one of the most significant challenges in blood cancer treatment.
The novel technology combines precision targeting with a dual mechanism of action, delivering a "double punch" that could significantly reduce relapse rates in leukemia patients while minimizing toxic side effects associated with conventional treatments.
Targeting the Root of Leukemia Recurrence
High relapse rates in leukemia and other blood cancers are largely attributed to LSCs, which can evade standard chemotherapy by retreating to the bone marrow. These stem cells can remain dormant for extended periods before proliferating and causing disease recurrence.
"It's important in leukemia, lymphoma or other blood cancers that we actually target and eliminate these stem cells, because as long as any are remaining, they can cause relapse and secondary cancers," explained Abhisek Dwivedy, first author of the study published in Advanced Functional Materials.
The research team, led by Professor Xing Wang of the University of Illinois, focused on developing aptamers—single-stranded DNA molecules that can bind to specific protein targets—designed to recognize two distinct biomarkers on acute myeloid leukemia stem cells: CD117 and CD123.
Dual-Target Approach Enhances Specificity
A key innovation in this research is the use of multiple biomarkers to enhance targeting specificity. Many cancer biomarkers are also expressed on healthy cells, making single-target approaches problematic.
"A big thing we showed in this study is that having two targets is better than one in terms of selectivity," said Professor Wang. "There are known antibody-drug conjugates for blood cancers that target one marker, but that marker is also found on a lot of healthy cells. So there is a lot of toxicity associated with antibody conjugates."
The researchers arranged the aptamers into precise patterns using their Designer DNA-Architecture (DDA)-based platforms, creating structures that can differentiate target cells from non-target cells with high precision.
Double Mechanism Delivers Enhanced Potency
The aptamers themselves demonstrated cytotoxic effects by disrupting MAP kinase and apoptosis signaling pathways in cancer cells. When loaded with the anticancer drug daunorubicin, creating a DDA-drug conjugate (DDA-DC), they delivered a powerful combination therapy.
Laboratory testing revealed impressive results. After 72 hours, the aptamers alone reduced cancer cells in culture by 40%. When combined with daunorubicin, the DDA-DC eliminated cancer cells at a dose 500 times smaller than the standard dosage of daunorubicin alone.
In mouse models with leukemia, the drug-aptamer conjugates achieved the same efficacy at one-tenth the clinical standard dose, with no observed off-target effects.
"This was exciting to us, because in cancer research, what we see in vitro is not always what we see in the body. Yet we saw excellent survivability and tumor reduction in the mice treated with our aptamer-drug conjugates, at one-tenth of the therapeutic dose, and no off-target effects," Wang noted.
Overcoming Drug Delivery Challenges
The aptamer technology also addresses a critical challenge in cancer drug delivery. Many potent anticancer drugs, including daunorubicin, have difficulty crossing cell membranes efficiently.
"This is especially important for drugs like daunorubicin, because the drug on its own cannot cross the cell membrane easily. But aptamers can carry it in," Dwivedy explained.
This enhanced delivery mechanism allows for lower drug dosages while maintaining or improving efficacy, potentially reducing the severe side effects associated with traditional chemotherapy regimens.
Future Applications Beyond Leukemia
The researchers are now working to expand their suite of drug-carrying DNA aptamers by identifying key biomarker combinations for other cancer types and exploring combinations with different therapeutic agents.
"Every cancer cell has a signature in its surface biomarkers. If we can find markers that are present uniquely in cancer cells, we can target other cancer types as well," said Dwivedy.
The technology's versatility may extend beyond cancer treatment. The researchers note that pairing drugs with DNA molecules is relatively straightforward compared to protein-based delivery systems, opening possibilities for broader therapeutic applications.
The research was supported by the National Institutes of Health and the National Science Foundation, with Professor Wang affiliated with the Cancer Center at Illinois, the Carl R. Woese Institute for Genomic Biology, and the Holonyak Micro and Nanotechnology Lab at the University of Illinois.
