Future

Magnetic Hyperthermia Therapy

In view of the development trend and concept of the integration of diagnosis and treatment, we hope that the engineering magnetosome as a contrast agent can provide further potential treatment. And then we came up with magnetic hyperthermia.

What is Magnetic Hyperthermia Therapy?

Magnetic hyperthermia therapy was first attempted in 1957 to treat cancers that had metastasised to the lymph nodes. The experimential animal was put in the copper spiral (Figure 1) and it built upon the principles of localised hyperthermia therapy by using magnetic nanoparticles and incorporating an alternating magnetic field to generate heat^[1].

In fact, many studies have shown that magnetic nanoparticles as a potential mediator have been proven to be useful in magnetic hyperthermia therapy for a variety of tumors^[2]-[5], including breast cancer^[6].

But some obstacles remain for optimal magnetic hyperthermia therapy application, especially inaccuracy intratumoural heating at the tumour site. Fortunately, MagHER2somes targeting HER2-positive breast cancer can fully meet the requirements of the magnetic hyperthermia medium and reduce the damage to healthy cells caused by unspecificity.

In addition, due to their thermally stable magnetic moment, the magnetosomes produce a larger amount of heat than the smaller super-paramagnetic chemically synthesised nanoparticles^[7].

Therefore, the application of an alternating magnetic field to magnetic nanoparticles could be applied to induce magnetic hyperthermia and partially or completely destroy small occult lesions limiting the extent of or completely avoiding the need for surgical intervention^[8].

Experiments conducted on mice showed that the temperature of magnetic hyperthermia therapy could reach as high as 46℃ when using the magnetosomes as the medium for magnetic hyperthermia. And after 30 days of treatment, tumors in some mice disappeared^[7].

Figure 1. The set-up used to carry out the treatment of the mice by positioning the mice inside the copper coil and by applying an alternating magnetic field.

How to Apply Magnetic Hyperthermia Therapy?

In order to minimize the potential side effects arising during the clinical treatments, the quantity of nanoparticles administered needs to be as small as possible but still retaining the desired effect.

We will refer to the experience of existing studies to determine the amount of contrast agent.

Studies applied to breast cancer showed that the core diameter of magnetosomes was 10nm, and the temperature could be raised to 71℃ in 242 seconds at a certain concentration (21 mg ± 9 magnetite per 299 mm³ target tissue) under an appropriate alternating magnetic field size (field amplitude: 6.5 kA/m, frequency: 400 kHz)^[9].

Figure 2. When applying magnetic hyperthermia therapy with breast cancer, the temperature could be raised to 71℃ in 242 seconds at a certain concentration under an appropriate alternating magnetic field size.

This gives us great encouragement, indicating that the effect of high temperature by using trace magnetosomes in magnetic hyperthermia therapy can be expected.

And last but not least is what stage of patients we apply magnetic hyperthermia therapy to and what kind of criteria we follow.

In fact, magnetic hyperthermia therapy is often is applied as an adjunctive therapy with various established cancer treatments such as radiotherapy and chemotherapy. Several phase III trials comparing radiotherapy alone or with hyperthermia have shown a beneficial effect of hyperthermia (with existing standard equipment) in terms of local control (e.g. recurrent breast cancer)^[10]. In addition, we will strictly follow quality assurance guidelines for superficial hyperthermia clinical trials^[11].

Overproduction

All applications using magnetosome particles so far have been hampered by their poor availability due to the fastidious growth requirements of magnetotactic bacteria and the low magnetosome content of biomass. Therefore, an attractive possibility to increase magnetosome bioproduction would be genetic engineering or overexpression of biosynthesis pathway genes in native or foreign hosts^[12].

In a study, researchers present a strategy for the overexpression of magnetosome biosynthesis genes in the alphaproteobacterium Magnetospirillum gryphiswaldense MSR-1 by chromosomal multiplication of individual and multiple magnetosome gene clusters via transposition.

While stepwise amplification of the mms6 operon resulted in the formation of increasingly larger crystals (increase of ∼35%), the duplication of all major magnetosome operons (mamGFDC, mamAB, mms6, and mamXY, comprising 29 genes in total) yielded an overproducing strain in which magnetosome numbers were 2.2-fold increased^[12].

Therefore, in the future, we will use this method to control the production of magnetosome to achieve the overproduction of magnetosome, which will help us to use MagHER2some as a real product for the benefit of doctors and patients.

Figure 3. Overproduction of magnetosome.

Size Control

It is well established that various physical characteristics of magnetic nanoparticles, such as sedimentation stability and magnetic remanence, are functions of their size^[13]. In order to obtain a uniform and stable contrast agent product, we hope to produce the magnetosome with narrow size distribution and control the particle size of the magnetosome to our desired size — 20nm.

Although sorting the obtained magnetosomes is a convenient way, it is not economical. We hope to further control the particle size of the magnetosomes by using biology method in the future.

Existing studies have shown that the size of magnetosomes is affected by many factors. In a study, the size of magnetosomes cultured in the presence of Zn and Ni (23 ± 3 nm and 25 ± 5 nm, respectively) is considerably higher than that of magnetosomes in the control set (15 ± 3 nm)^[14].

Interestingly, the size of the magnetosome is not constant, and both the size and the heating power of the magnetosome will be reduced during the magnetic hyperthermia that we wish to apply. But it turns out that this change doesn't block antitumor activity^[15]. In the future, we'll be able to control the conditions that affect the size of magnetosomes to make sure that the final MagHER2somes are superparamagnetic with sizes smaller than 20 nm and the overall particle size distribution is narrow so that the particles have uniform physical and chemical properties^[16].

Figure 4. Control the size of magnetosome.

Targeted Platform

In the past work, we have successfully developed an engineered contrast agent MagHER2some which specifically targets HER2-positive breast cancer cells. The core technology we adopted is to display anti-HER2 antibodies on the surface of magnetosome taking advantage of the efficient combination of ZZ domain and Fc region. In the same way, we can design diverse scFv modified magnetosomes according to different tumor targets. Looking forward to the future, we aim to develop a versatile targeted imaging platform apply to the clinical diagnosis of more types of tumors (Table 1).

Cancer	Target
Hepatocellular Carcinoma	AFP^[17], Arginase-1^[18], GPC3^[19]
Gastric Cancer	CD133^[20], E-cadherin^[21]
Lung Cancer	CEA^[22][23], CYFRA21-1^[22][23]
Non Hodgkin's lymphoma	CD20^[24]
Pancreatic Cancer	5mg
Vitamin B₁₂	uPAR^[25], SSTR^[26]

Table 1. Specific targets that we can use for different types of tumors.

References

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[12]. Lohße, A., Kolinko, I., Raschdorf, O., Uebe, R., Borg, S., Brachmann, A., Plitzko, J. M., Müller, R., Zhang, Y., & Schüler, D. (2016). Overproduction of Magnetosomes by Genomic Amplification of Biosynthesis-Related Gene Clusters in a Magnetotactic Bacterium. Applied and environmental microbiology, 82(10), 3032–3041. https://doi.org/10.1128/AEM.03860-15

[13]. Hergt, R., Hiergeist, R., Zeisberger, M., Schüler, D., Heyen, U., Hilger, I., & Kaiser, W. A. (2005). Magnetic properties of bacterial magnetosomes as potential diagnostic and therapeutic tools. Journal of Magnetism and Magnetic Materials, 293(1), 80-86. doi:10.1016/j.jmmm.2005.01.047

[14]. Kundu, S., Kale, A. A., Banpurkar, A. G., Kulkarni, G. R., & Ogale, S. B. (2009). On the change in bacterial size and magnetosome features for Magnetospirillum magnetotacticum (MS-1) under high concentrations of zinc and nickel. Biomaterials, 30(25), 4211–4218. https://doi.org/10.1016/j.biomaterials.2009.04.039

[15]. Alphandéry, E., Idbaih, A., Adam, C., Delattre, J. Y., Schmitt, C., Gazeau, F., Guyot, F., & Chebbi, I. (2019). Biodegraded magnetosomes with reduced size and heating power maintain a persistent activity against intracranial U87-Luc mouse GBM tumors. Journal of nanobiotechnology, 17(1), 126. https://doi.org/10.1186/s12951-019-0555-2

[16]. Sun, Shouheng, and Hao Zeng. “Size-controlled synthesis of magnetite nanoparticles.” Journal of the American Chemical Society vol. 124,28 (2002): 8204-5. doi:10.1021/ja026501x

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[19]. Nakatsura, T., & Nishimura, Y. (2005). Usefulness of the novel oncofetal antigen glypican-3 for diagnosis of hepatocellular carcinoma and melanoma. BioDrugs : clinical immunotherapeutics, biopharmaceuticals and gene therapy, 19(2), 71–77. https://doi.org/10.2165/00063030-200519020-00001

[20]. Hashimoto, K., Aoyagi, K., Isobe, T., Kouhuji, K., & Shirouzu, K. (2014). Expression of CD133 in the cytoplasm is associated with cancer progression and poor prognosis in gastric cancer. Gastric cancer : official journal of the International Gastric Cancer Association and the Japanese Gastric Cancer Association, 17(1), 97–106. https://doi.org/10.1007/s10120-013-0255-9

[21]. Zhou, Y. N., Xu, C. P., Han, B., Li, M., Qiao, L., Fang, D. C., & Yang, J. M. (2002). Expression of E-cadherin and beta-catenin in gastric carcinoma and its correlation with the clinicopathological features and patient survival. World journal of gastroenterology, 8(6), 987–993. https://doi.org/10.3748/wjg.v8.i6.987

[22]. Fiala, O., Pesek, M., Finek, J., Benesova, L., Minarik, M., Bortlicek, Z., & Topolcan, O. (2014). Predictive role of CEA and CYFRA 21-1 in patients with advanced-stage NSCLC treated with erlotinib. Anticancer research, 34(6), 3205–3210.

[23]. Dansheng Lei, Pei Feng, Yu Jing, Kun Wang, & Yi Zhu. (2015). Tissue polypeptide antigen joint progrp, cea, nse, SCC, cyfra21-1 value in the diagnosis and treatment of lung cancer. Cancer Prevention Research(05), 488-492.

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[25]. Gorantla, B., Asuthkar, S., Rao, J. S., Patel, J., & Gondi, C. S. (2011). Suppression of the uPAR-uPA system retards angiogenesis, invasion, and in vivo tumor development in pancreatic cancer cells. Molecular cancer research : MCR, 9(4), 377–389. https://doi.org/10.1158/1541-7786.MCR-10-0452

[26]. Ragozin, E., Hesin, A., Bazylevich, A., Tuchinsky, H., Bovina, A., Shekhter Zahavi, T., Oron-Herman, M., Kostenich, G., Firer, M. A., Rubinek, T., Wolf, I., Luboshits, G., Sherman, M. Y., & Gellerman, G. (2018). New somatostatin-drug conjugates for effective targeting pancreatic cancer. Bioorganic & medicinal chemistry, 26(13), 3825–3836. https://doi.org/10.1016/j.bmc.2018.06.032

Team:ZJU-China/Future