Introduction to cancer immunotherapy using highly active NK cells

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Past problems of NK cell therapy

As we described in this website, NK (natural killer) cell therapy is expected to be effective for the treatment of cancer. However, important results inconsistent with such an expectation were reported in the past.

Failure of LAK cells

In the 1980’s, Rosenberg’s team in the United States published an innovative report that, when lymphocytes in patients’ blood are isolated and cultured with interleukin 2 (IL-2), they are activated and when they were returned to patients’’ bodies, they showed marked anticancer effect.
The activated lymphocytes described in this study report are called “LAK cells” and were frequently used for the treatment of cancer patients also in Japan. Later, it turned out that the lymphocyte with antitumor effect in LAK cells are mainly activated NK cells. However, when the efficacy of LAK cells was examined again in many cancer patients using a strict method, these cells did not show the initially reported efficacy. Because of this finding, cancer treatment using LAK cells produced by activating lymphocytes only with IL-2 became less common. After that, development of a method using a CD3 antibody by which activated T cells can be easily increased to a large amount made T cell (lymphocyte) therapy a mainstay of immune cell therapy currently provided at private healthcare facilities in Japan.

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Problems of LAK cells

There are many possible reasons that LAK cells were not markedly effective for cancer. Among them, three main reasons are summarized below.

1. LAK cells are peripheral blood lymphocytes stimulated only by IL-2 for a short period of 5 to 7 days. Using this method, NK cells were not increased sufficiently (at most, dozens of times more) and the number of cells actually administered was not high enough.

2. Short-term stimulation only with IL-2 did not result in strong cytotoxicity because patients’ NK cells weakened by cancer cells contained only a small number of cells that actually attack cancer cells.

3. Activated NK cells that were administered could not reach cancer lesions because they did not have the marker called, “chemokine receptor”, which serves as a guide when NK cells go from blood vessels to cancer lesions.

A major problem of the past cancer therapy using LAK cells stimulated by and cultured with IL-2 alone (among them, those with an antitumor effect are considered to mainly consist of NK cells) is considered to be the fact that all of the above factors, the number of administered cells, chemokine receptor and cytotoxicity against cancer cells, were not sufficient to confront the formidable enemy, e. g., cancer.

Highly active NK cell therapy at the New City Osaki Clinic solves these problems and weak points.

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Cancer immunotherapy

Immune system | Cancer immunotherapy | Highly active NK cell therapy | Problems of highly active NK cells | Characteristics of highly active NK cells | “immunity-enhancing effect” of highly active NK cells | Recommendation of highly active NK cell therapy