Aptamer-Drug Conjugates of Active Metabolites of Nucleoside Analogs and Cytotoxic Agents Inhibit Pancreatic Tumor Cell Growth

Abstract

Aptamer-drug conjugates (ApDCs) have the potential to improve the therapeutic index of traditional chemotherapeutic agents due to their ability to deliver cytotoxic drugs specifically to cancer cells while sparing normal cells. This study reports on the conjugation of cytotoxic drugs to an aptamer previously described by our group, the pancreatic cancer RNA aptamer P19. To this end, P19 was incorporated with gemcitabine and 5-fluorouracil (5-FU), or conjugated to monomethyl auristatin E (MMAE) and derivative of maytansine 1 (DM1). The ApDCs P19-dFdCMP and P19-5FdUMP were shown to induce the phosphorylation of histone H2AX on Ser139 (γ-H2AX) and significantly inhibited cell proliferation by 51%–53% in PANC-1 and by 54%–34% in the gemcitabine-resistant pancreatic cancer cell line AsPC-1 (p ≤ 0.0001). P19-MMAE and P19-DM1 caused mitotic G2/M phase arrest and inhibited cell proliferation by up to 56% in a dose-dependent manner when compared to the control group (p ≤ 0.001). In addition, the cytotoxicity of P19-MMAE and P19-DM1 in normal cells and the control human breast cancer cell line MCF7 was minimal. These results suggest that this approach may be useful in decreasing cytotoxic side effects in non-tumoral tissue.

AptaBlocks: Accelerating the Design of RNA-based Drug Delivery Systems

“…Complementing the in silico validation of AptaBlocks, we also validated its ability to design sticky bridges in vitro on a pancreatic cancer cell model using aptamer tP19 as described in [16] and a siRNA as shown in Fig. 5A.…”

“…In the same pancreatic cancer model, but in contrast to conjugating a siRNA to the aptamer, AptaBlocks has also been successful in designing a sticky bridge for an aptamer-drug conjugate. This design has been implemented experimentally, verified in vitro, and described in detail in [16].…”

“…Despite our focus on ssRNA or dsRNAs as cargoes, it is important to note that our approach extends naturally to a multitude of other cargoes. As a case in point, a universal bridge designed with AptaBlocks is currently explored in an experimental setting, facilitating the conjugation of cytotoxic drugs and RNA aptamer tP19, targeting pancreatic tumor cell growth [16]. Given the rapid development of efficient in vitro selection technologies allowing for the generation of highly target-specific and target-affine aptamers, we anticipate that with its general design strategy, AptaBlocks will further accelerate the development of flexible and effective drug delivery systems.…”

Emerging cancer-specific therapeutic aptamers

“…However, because of their high toxicity, neither MMAE nor DM1 can be used as cytotoxic drugs in their own right in clinic. As an targeted delivery of both MMAE and DM1, truncated pancreatic cancer-targeted aptamers have been chemically conjugated to MMAE and DM1 to construct aptamer-drug conjugates (21). Aptamer-MMAE and -DM1 show significant pancreatic cancer cell-specific cytotoxicity, but non-toxic effects in non-targeted breast cancer cells (MCF7) or normal skin fibroblast cells (BJ).…”

Treating Tumors at Low Drug Doses Using an Aptamer–Peptide Synergistic Drug Conjugate

“…[1][2][3][4] However, drug combinations are typically administered at doses close to the maximum tolerated dose (MTD) of each drug. [7] Several aptamer drug conjugates have been reported, but they are limited by low drug payloads (one drug per aptamer), [8][9][10][11][12] or incompatibility with drugs other than DNAi ntercalators such as doxorubicin (DOX), [13][14][15][16] making them unusable for delivering drug combinations. [5,6] Herein, an ovel strategy using aptamers for targeted and controlled combination drug dosing is reported to achieve ap otent antitumor response at doses far below individual drug MTDs.This approach entails the generation of aptamerpeptide drug constructs for the effective delivery of multiple therapeutic agents at defined molar ratios.T he targeted delivery of acombination of drugs is demonstrated, including one drug with known solubility issues,with highly controlled stoichiometry to achieve efficacy at unprecedentedly low drug doses.Aptamers offer aversatile targeting platform for awide range of tumors,with affinities and specificities comparable to antibodies.O wing to their small size,t hey also penetrate deeper into tumors.…”