Nanoparticle-based combinatorial therapy for targeted treatment of cancer

Cancer is a group of diseases caused by aberrant cell growth and division that is capable of spreading to other healthy organs. Conventional anticancer therapies (chemotherapies which are chemical agents used to kill the cancer cells) are associated with serious side effects. One problem with chemotherapy is that it is cytotoxic toward healthy tissues as well as cancer cells. Additionally, many cancers can develop drug resistance so that certain chemotherapeutic drugs no longer work. One strategy currently used to combat drug resistance is to combine more than one chemotherapy, but this approach is still associated with serious side effects. Ciprofloxacin derivatives are currently gaining great attention in the field of cancer therapy. Ciprofloxacin is an antimicrobial agent currently used to treat bacterial infections. However, it has been found that some chemical modifications in the structure of ciprofloxacin can result in changing its activity from an antibacterial to an anticancer drug. Therefore, CIP2b, which is a newly synthesized ciprofloxacin derivative, was used as an alternative for one of the chemotherapies in combinational therapies. To solve the distribution issue of the anticancer drug to all body organs, scientists developed a nanocarrier (or nanoparticles (NPs)) that would enhance the delivery of the drug to the tumor. Most normal healthy tissues are impermeable to molecules with a diameter larger than 5 nm. However, the tumors are more permeable to larger macromolecules, allowing NPs with diameters of up to 600 nm to penetrate and accumulate at the tumor site. Therefore, NPs can be used to take advantage of the increased permeability of tumors by what is known as passive targeting. Herein, we are studying the effect of novel drug combinations using an NP-based delivery system to treat aggressive forms of cancer.

In the first study, combination therapy of CIP2b in its soluble form and soluble paclitaxel (PTX), first-line chemotherapy for endometrial cancer (EC), was initially tested against different aggressive forms of EC cell lines that possess different mutations. The results showed that our novel drug combination was effective against all type II (aggressive EC) cell lines where the drug combination significantly enhanced the cell cytotoxicity compared to a single treatment. In addition, the results showed a significant increase in drug accumulation at the tumor site when the cells were treated with the combination of PTX and CIP2b compared to the single treatment. This drug combination was found to work by at least 4 different mechanisms. Moreover, the drug combination of PTX and CIP2b was also tested on animals and for that purpose, CIP2b NPs were prepared and combined with PTX and tested against a mouse EC model. The results showed that the group that received the combination of CIP2b NPs and PTX exhibited a significant reduction in tumor size compared to the untreated group. In another animal experiment carried out to determine the distribution of CIP2b in tumors and main organs, it was found that CIP2b shifted the drug distribution from the healthy organs toward the tumor. A toxicity study showed that this drug combination was safe. Thus, the combination of CIP2b and PTX may have potentially superior therapeutic activity over current chemotherapeutic combinations. This study highlighted the importance of this novel drug combination in treating aggressive forms of EC.

Since this drug combination had the potential to inhibit drug pumps (present in the blood-brain barrier (BBB)) which can pump PTX out of the brain and therefore decrease the effectiveness of PTX against brain tumors, we were interested in testing this combination against brain cancer. Therefore, in the second study, the novel combination of CIP2b and PTX was tested against one of the most aggressive forms of brain cancer, glioblastoma multiforme (GBM). In order to test our drug combination's ability to penetrate the BBB cells, the combination therapy of novel soluble CIP2b and soluble PTX was initially tested against a BBB cell line. The results showed that our drug combination significantly increased PTX penetration across the BBB when compared to PTX alone while the cytotoxicity assay against GBM cells showed that there were no differences between PTX alone or when PTX was combined with CIP2b. This indicated that the role of CIP2b is to help the PTX penetration across the BBB not to directly enhance the cytotoxicity of PTX. To confirm whether CIP2b enhances PTX accumulation in the brain, CIP2b was formulated into NPs. It is important to know that the plasma membrane of the BBB is negatively charged. Therefore, positively charged NPs are expected to enhance the electrostatic interaction with negatively charged plasma membrane which can potentially increase BBB permeability and accumulation of PTX in the brain accumulation. Accordingly, positively charged CIP2b NPs were prepared and conjugated with PTX, and then PTX accumulation in the brain was tested in mice. The results showed that mice receiving the combination of CIP2b NPs and PTX exhibited a significantly higher accumulation of PTX in the brain compared to PTX alone. Presented data highlighted different applications of this novel drug combination and showed its validity to treat different forms of cancer. Additionally, it showed targeted NPs as a promising efficient delivery system for cancer treatment.