Photoimmunotherapy

Photoimmunotherapy (PIT), also referred to as photothermal immunotherapy and photothermalimmunology, is an oncological treatment that combines photodynamic therapy of tumor with immunotherapy treatment. Combining photodynamic therapy with immunotherapy enhances the immunostimulating response and has synergistic effects for metastatic cancer treatment.[1][2][3]

PIT is type of molecular targeted cancer therapy, which allows the selective destruction of cancer cells without any damage to normal tissues. It is a light-based cancer therapy, which was developed by Professor Kobayashi and his colleagues at National Cancer Institute, Bethesda, Maryland.

Conventional photodynamic therapy (PDT) uses a non-specific photosensitizer which can be activated by a non-ionizing light to kill cancer cells. Photosensitizers are molecules that rapidly destroy cells though the production of reactive oxygen species (ROS) when exposed to light at specific wavelength.[4] However, this PDT treatment results in serious side effects because non-targeted photosensitizers are also taken up by normal tissues.

PIT treatment avoids the side effects problem through the creation of a targeted-photosensitizer, which involves two components: a monoclonal antibody (mAb) which recognizes specific proteins on the surface of cancer cells, and a non-targeted photosensitizer. Even though the new mAb-based photosensitizers are distributed throughout the body, it can be activated by light for targeted PIT only when bound to specific proteins on cancer cellular membrane.[5]

The research team at Professor Kobayashi’s lab coupled anti-tumor antibodies targeting human epidermal growth factor receptors to a phthalocyanine dye, IRDye 700DX,[6] which is activated by near-infrared light. IRDye 700DX was chosen for its hydrophilicity and strong cytotoxicity induced upon association with the cellular membrane and subsequent activation.[5] A variety of cancers, such as breast and pancreatic cancers over-express epidermal growth factor receptors.[7] This new photosensitizing compound utilizing IRDye 700DX NHS Ester was referred to as “mAb-IR700 conjugates”.

In Vitro studies showed that mAb-IR700 killed tumor cells seconds after the near-infrared light irradiation. There was also a positive correlation between the intensity of excitation light and percentage of cell death. Infrared light alone or mAb-IR700 conjugate alone did not cause any damage to normal cells. When tumor-xenografted mice were treated with mAb-IR700 and near-infrared light, significant tumor shrinkage was observed. With fractionated administration of mAB–IR700 conjugate followed by systematic repeated NIR light irradiation to the tumor, 80 percent of tumor cells were eradicated and the mice’s survival were significantly prolonged.[8] Based on the current hypothesis, cell death induced by PIT was caused by rapid expansion of local water upon the formation of holes in the membrane.

Another desirable feature of PIT using mAb-IR700 conjugate is that it also emits fluorescence light upon activation. Therefore before PIT, mAb-IR700 can be administered at a lower dosage to guide the application of excitation light to tumor tissues, further minimizing unnecessary light exposure to surrounding tissues.

PIT is a promising highly selective and clinically feasible therapeutic method for treatment of mAb-binding tumors with minimal off-target effects. For future directions, researchers are trying to conjugate a variety of other monoclonal antibodies to phthalocyanine, creating a highly flexible therapeutic platform.

See also

References

  1. ↑ "Immunological responses triggered by photothermal therapy with carbon nanotubes in combination with anti-CTLA-4 therapy to inhibit cancer metastasis.". 2014. PMID 25331930. doi:10.1002/adma.201402996.
  2. ↑ Lin, Z.; et al. (2015). "Photothermal ablation of bone metastasis of breast cancer using PEGylated multi-walled carbon nanotubes.". PMID 25331930. doi:10.1038/srep11709.
  3. ↑ Chen, Q.; et al. (2016). "Photothermal therapy with immune-adjuvant nanoparticles together with checkpoint blockade for effective cancer immunotherapy.". PMID 25331930. doi:10.1038/ncomms13193.
  4. ↑ Park, S (2007-05). "Delivery of photosensitizers for photodynamic therapy". Korean J Gastroenterol 49 (5): 300–313
  5. 1 2 Mitsunaga, M; Ogawa, M; Kosaka, N; Rosenblum, L. T; Choyke, P. L; Kobayashi, H (2011). "Cancer cell-selective in vivo near infrared photoimmunotherapy targeting specific membrane molecules". Nature Medicine. 17 (12): 1685–1691. PMC 3233641 Freely accessible.
  6. ↑ Peng, Xinzhan; Daniel R. Draney; William M. Volcheck; Gregory R. Bashford; Donald T. Lamb; Daniel L. Grone; Yonghong Zhang; Craig M. Johnson (14 February 2006). "Phthalocyanine dye as an extremely photostable and highly fluorescent near-infrared labeling reagent". Proc.SPIE 6097, Optical Molecular Probes for Biomedical Applications, 60970E. 6097. doi:10.1117/12.669173.
  7. ↑ McKeage K, Perry CM., Trastuzumab: a review of its use in the treatment of metastatic breast cancer overexpressing HER2., Drugs. 2002;62(1):209-43.
  8. ↑ Makoto Mitsunaga, Takahito Nakajima, Kohei Sano, Peter L. Choyke, and Hisataka Kobayashi, (2012) Near-infrared Theranostic Photoimmunotherapy (PIT): Repeated Exposure of Light Enhances the Effect of Immunoconjugate, Bioconjugate Chem., 2012, 23 (3), 604–609

Bibliography

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