Nano-Micelles efficacy depends on tumor c-Myc expression

Significance 

The Innovation Center of NanoMedicine together with the group of Prof. Yu Matsumoto of Otorhinolaryngology and Head and Neck Surgery and the group of Prof. Horacio Cabral of the Department of Bioengineering in the University of Tokyo showed that the efficacy of polymeric nano-micelles with different drug activation profile depends on the expression level of c-Myc, one of the major proto-oncogenes, has been developed. The new research is currently published in the journal ACS Nano.

It is known that c-Myc is involved in cancer cell proliferation and angiogenesis and changes the cell cycle, suppresses normal cell differentiation, and promotes cancer metastasis. It is a typical proto-oncogene that regulates many genes related to growth factors and is known to be involved in developing of many cancers, such as chromosomal translocation in Burkitt lymphoma. Therefore, drug discovery research is being conducted worldwide as an anticancer drug targeting this transcription factor that can directly attack cancer stem cells. However, since embryonic lethality occurs in c-Myc knockout mice, c-Myc is considered as an essential gene for living cells, and selective delivery to cancer tissues is an important key to developing its inhibitors. Besides, c-Myc is also known as a factor necessary for the initial induction of iPS cells. In the future this inhibition can be expected to be applied as a technology that can also be used to suppress iPS cell-derived carcinogenesis.

JQ1H, which is a structural analogue of JQ1H, a typical indirect c-Myc inhibitor, was encapsulated inside functional nano-micelles, and their efficacy was evaluated. JQ1 binds to a bromodomain protein called BRD4, which is involved in the activation of RNA polymerase II regulating the expression of c-Myc, to inhibit this stream strongly. As a result, the activity of RNA polymerase is weakened and c-Myc expression is down-regulated. Although JQ1 was expected as a promising epigenome drug due to its strong gene expression inhibition, it has an extremely short half-life in vivo due to its fast kidney excretion and rapid clearance after administration. Additionally, JQ1 is almost insoluble in water. These properties of JQ1 became big issues to develop it as an effective drug. The polymeric nano-micelles developed so far at the Innovation Center of NanoMedicine (iCONM), for anticancer therapy, demonstrated (1) stabilization of encapsulated drugs, (2) suppression of kidney excretion, (3) EPR (selective drug delivery to cancer tissues) mediated tumor accumulation, and (4) drug release based on tumor acidosis. This time, we confirmed good antitumor activity in mice transplanted with tongue cancer, melanoma and pancreatic cancer using JQ1-equipped nano-micelles.

Nano-micelles containing JQ1H leak into the tumor tissue from blood vessels after systemic administration due to the so-called EPR effect. Tumor tissues are rich in lactic acid due to its enhanced glycolysis and is more acidic than normal tissues. The authors prepared two types of nano-micelle; one in which hydrophobic JQ1H were linked to a amphiphilic block polymer composed of hydrophilic polyethylene glycol block and hydrophobic poly-amino acid block using 3-aminopropionaldehyde (aliphatic aldehyde) linker and the other micelle in which JQ1H was linked with polymer via p-aminomethylbenzaldehyde (aromatic aldehyde) linker. An amphiphilic block polymer was synthesized and used as a base material for nano-micelles. When it was self-assembled in water to a micellar structure and administered to cancer-bearing mice, antitumor activity was achieved.

When the linker is an aliphatic aldehyde or when it is an aromatic aldehyde, the release pattern of the drug differs greatly depends on the acidity. The former releases the drug rapidly, and the latter releases the drug slowly. Therefore, the former nano-medicine was named FR-JQ1H/m and the latter was named SR-JQ1H/m. The antitumor activity of these nano-micelles differ greatly depending on the expression level of c-Myc. While, FR-JQ1H/m is more effective for tumors with high c-Myc expression, SR-JQ1H/m is more effective for tumors with low c-Myc expression.

The authors believe that the selection of nano-micelles according to the expression level of biomarkers will be an important step toward the realization of personalized medicine.

Nano-Micelles efficacy depends on tumor c-Myc expression - Medicine Innovates
Fig. 1: Different drug release profile depending on the linker used for block-copolymers of nano-micellesFR-JQ1H/m with aliphatic aldehyde linker: Fast drug release in gradually elevated aciditySR-JQ1H/m with aromatic aldehyde linker: Slow drug release in gradually elevated acidityDrug release curve of FR-JQ1 and SR-JQdepending on the pH change of tumor tissues Credit: 2021 Innovation. Center of NanoMedicine

About the author

Prof. Kazunori Kataoka received Ph.D. degree in polymer chemistry from the University of Tokyo in 1979. He joined the faculty at Tokyo Women’s Medical College (1979-1989) and then at Tokyo University of Science (1989-1998). He moved to the University of Tokyo on 1998 as full Professor of Biomaterials at Graduate School of Engineering. He has been appointed joint position as Professor of Clinical Biotechnology at Center of Disease Biology and Integrative Medicine, the University of Tokyo Medical School (2004~2016). Since 2016, he has assumed Director General at Innovation Center of NanoMedicine (iCONM), Kawasaki Institute of Industry Promotion.

Dr. Kataoka is currently the Member of the Science Council of Japan, the Foreign Member of the United States National Academy of Engineering (NAE), and the Fellow of the United States National Academy of Inventors (NAI). He has received several awards, including Clemson Award from the Society for Biomaterials USA (2005), Founder’s Award from the Controlled Release Society (2008), Humboldt Research Award (2012), Leo Esaki Prize (2012), Gutenberg Research Award (2015), and Princess Takamatsu Cancer Research Fund Prize (2017). In 2018, he was installed Doctor Honoris Causa (Dr.h.c.) at Johannes Gutenberg University Mainz, Germany.

Reference

Hitoshi Shibasaki, Hiroaki Kinoh, Horacio Cabral*, Sabina Quader, Yuki Mochida, Xueying Liu, Kazuko Toh, Kazuki Miyano, Yu Matsumoto, Tatsuya Yamasoba, and Kazunori Kataoka* .Hitoshi Shibasaki et al, Efficacy of pH-Sensitive Nanomedicines in Tumors with Different c-MYC Expression Depends on the Intratumoral Activation ProfileACS Nano (2021). DOI: 10.1021/acsnano.1c00364

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