Loss of Tumor Antigens
There are two types of tumor antigens: “tumor-specific antigens (neoantigens)” that exist only on cancer cells, and “tumor-associated antigens” that are also present on normal cells but are overexpressed on cancer cells.
As cancer cells grow, gene mutations are likely to occur, changing tumor antigens. Therefore, T cells (killer T cells and CAR-T cells) cannot recognize or attack these antigens. This is the mechanism by which the effectiveness of CAR-T cell therapy and killer T cell therapy targeting tumor-associated antigens such as CD19, HER2, and Claudin 18.2 is often reduced. On the other hand, neoantigens are abnormal peptides that arise from gene mutations in cancer cells and are not present on normal cells. They are presented on the cell surface via MHC class I molecules. Killer T cells (CD8-positive T cells) recognize these as foreign substances and attack them. As cancer cells grow, they reduce MHC class I molecule expression, preventing neoantigens from being presented on the surface and thus attempting to evade the immune system. However, cells with reduced MHC class I molecule expression are recognized by NK cells and become prey.

Recruitment of Immunosuppressive Cells in the Tumor Microenvironment
Cancer cells do not exist in isolation; they enlist the help of surrounding normal cells to create an “immunosuppressive” environment (tumor microenvironment) that strongly suppresses the activity of immune cells. Cancer cells actively recruit regulatory T cells (Tregs), directly inhibiting the activity of killer T cells or causing them to release suppressive cytokines (TGF-β and IL-10), making it difficult for an immune response to occur against cancer cells. Myeloid suppressor cells (MDSCs), which, like Tregs, possess strong immunosuppressive capabilities, are a population of immature myeloid cells that normally appear temporarily during inflammation, but are recruited from the bone marrow by factors released by cancer cells and proliferate in tumor tissue and lymphoid tissue. MDSCs produce reactive oxygen species (ROS), nitric oxide (NO), etc., paralyzing the proliferation and function of T cells and suppressing the immune response to cancer. Fas ligand expressed on NK cells recognizes the FAS antigen expressed on Tregs and MDSCs, inducing apoptosis and eliminating them. On the other hand, macrophages are cells that normally engulf and eliminate foreign substances, but in a tumor environment, they change into a type called M2 macrophages (tumor-associated macrophages: TAMs) that help cancer cells survive. TAMs not only promote angiogenesis and help supply nutrients to cancer cells, but also release immunosuppressive factors that block attacks by T cells. NK cell exosomes contain miR146a,21,155, which promote the differentiation of M2 macrophages (immunosuppressive type) into M1 macrophages (immunostimulatory type).

Immune Brake of T Cells Caused by PD-L1 Expression
Activated T cells express a receptor called PD-1 on their surface. This is normally a brake switch that prevents damage to normal tissues by excessive immune responses. Cancer cells express large amounts of a molecule called PD-L1, which is a ligand for activating this switch, on their surface. Even when killer T cells recognize cancer cells and approach them, if the PD-L1 on the cancer cell binds to the PD-1 on the T cell, an inhibitory signal is transmitted inside the T cell, causing it to lose its ability to attack. Since NK cells cannot resolve this situation, it is necessary to block the PD-L1 on cancer cells using immune checkpoint inhibitors to release the immune brake.

Chronic Antigen Exposure Leads to T Cell Exhaustion Gene Expression
In cancer tissue, antigens are constantly present, leading to chronic stimulation of T cells. Under these conditions, T cell-derived exhaustion genes (BATF and TOX) are expressed, resulting in a state called “exhaustion.” Exhausted T cells highly express not only PD-1 but also multiple immunosuppressive receptors such as TIM-3 and LAG-3, losing their proliferative capacity, cytokine production capacity, and cytotoxic activity. Exosomes secreted by NK cells contain miR155, which suppresses the expression of exhaustion genes, thus preventing T cell exhaustion and restoring immune function.

Release of Immunosuppressive Cytokines
Cancer cells release cytokines (signaling molecules) that suppress the immune system, either by themselves or by acting on surrounding cells (tumor microenvironment). TGF-β (transforming growth factor beta) is a prime example; it not only directly suppresses the function of killer T cells and NK cells, but also activates fibroblasts to create a physical barrier, preventing immune cells from reaching cancer cells. IL-10 also works to reduce the function of antigen-presenting cells, thereby calming the overall immune response. Furthermore, these cytokines are known to impair dendritic cells, reducing their antigen-presenting ability.

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Treatment mechanism
• Role of NK cells
NK (natural killer) cells are innate immune cells that find, attack, and destroy cancer and virus-infected cells.
• Treatment flow:
1. Collect patient’s blood and isolate NK cells.
2. Activate NK cells in a dedicated facility and multiply them from hundreds of millions to billions.
3. The activated NK cells are returned to the patient’s body via an intravenous drip.

• Effects:
Activated NK cells are expected to attack cancer cells through circulation in the body, suppressing cancer growth or reducing cancer size. It is also expected to be effective in preventing recurrence and metastasis after surgery.

Features and expected effects
• Fewer side effects: Because it uses your own immune cells, it is said to have fewer side effects than transplanting someone else’s cells.
• Combination with other treatments: Synergistic effects can be expected when combined with other treatments such as chemotherapy and radiation therapy.
• Cancer prevention: With permission from the Ministry of Health, Labor and Welfare, it can also be used to replenish NK cells for cancer prevention.
At our hospital, in order to further increase the activity of NK cells, we inject exosomes secreted by NK cells intravenously to enhance the antitumor effect. It is expected to be more effective than conventional NK cell therapy, so we believe it is suitable for patients whose cancer is more advanced and whose immune system is weakened.

The progress of an example is shown below.

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It prevents unnecessary genes from functioning, creating individual cells and maintaining the normal functioning of our bodies.

However, when DNA methylation becomes abnormal, it can inhibit the function of genes necessary for each cell, or promote genes that should be suppressed.

For example, it has been found that when cancer cells are collected, abnormalities in DNA methylation are present. While cancer is normally prevented by the action of tumor-suppressing genes, in some cases, abnormalities in methylation can prevent these tumor-suppressing genes from functioning, leading to cancer development.

In such cases, it is believed that if DNA methylation can be normalized using drugs that control the epigenetic state, it may be possible to treat the cancer.

Can cancer be cured by reprogramming (resetting) cancer cells?

It is believed that repairing gene mutations or epigenetic abnormalities can reverse cancerous transformation back to normal.

Similar to the reprogramming of somatic cells into iPS cells, the concept of reprogramming cancer cells to return them to normal cells is becoming established.

There have been published reports of reprogramming mouse melanoma cells, which are cancer cells, and other research teams have also announced that when they added two types of chemical substances, including anticancer drugs, to human liver cancer stem cells in a culture dish, 85-90% of the cancer cells became normal liver cells after two days. Furthermore, they succeeded in reprogramming iPS cells by adding two genes and two types of chemical substances, and returning them to normal liver cells.

We have identified miR-520d, which promotes the formation of iPS cells in cancer cells, among the approximately 2700 types of miRNAs already known. We have found that small molecule compounds that inhibit the methylation-related enzymes HAT1 and KAT8 enhance the function of miR-520d. Furthermore, these compounds have been shown to upregulate the tumor suppressor gene p53, thereby inducing apoptosis in cancer cells. At our hospital, we propose cancer treatment by administering these compounds to demethylate and reprogram cancer cells. Several clinical cases have suggested efficacy against cancer, and no serious adverse events have been reported.

Reprogramming therapy, which involves administering genes or chemical substances to restore cells to a normal state, is expected to lead to treatments for cancer and diabetes. It has been reported that major pharmaceutical companies are focusing their development efforts on this therapy, as it is seen as a treatment with no side effects and the potential to cure even intractable diseases.

However, a problem exists: even if cancer cells are reprogrammed into normal cells, to actually achieve cancer treatment, it’s necessary to reprogram cancer cells in the living body, not just in a culture dish, with 100% efficiency. Generally, even early-stage cancers detected by imaging tests are thought to consist of 100 million cancer cells. Even if 99.9% of cancer cells could be reprogrammed into normal cells, 100,000 cancer cells would still be needed for recurrence, making it insufficient from the perspective of a complete cure.

Therefore, Saisei no Mori Clinic Roppongi has devised the Saisei no Mori cancer treatment method, which uses these small molecule compounds to shrink cancer to one-thousandth of its original size, a level at which cancer immunotherapy is effective, and then treats the remaining cancer cells in combination with NK cell therapy, macrophage activation therapy, and other therapies. It is expected to be particularly effective against advanced, highly malignant undifferentiated or poorly differentiated cancers. It can also be used as a second opinion for cancer treatment.

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NKT Cell Targeted Therapy
Monocytes (dendritic cell progenitor cells) are collected from the patient’s blood via apheresis and cultured in vitro to form dendritic cells. Then, the glycolipid “α-galactosylceramide (α-GalCer)” is bound to the CD1d molecule of the dendritic cells to create an “α-GalCer-presenting dendritic cell (α-GalCer-DC) complex,” which is then returned to the body via intravenous infusion. When NKT cells recognize this complex with a receptor called the invariant T cell receptor, they are activated en masse, releasing large amounts of the cytokine interferon-γ, which primarily calls upon NK cells (innate immunity) and killer T cells (CD8+ T cells) (adaptive immunity) to powerfully attack cancer cells. Activated NKT cells also attack cancer cells, but their direct cytotoxic activity is limited due to the small amount present in the body. Furthermore, some activated immune cells become memory cells (such as memory T cells) and remain in the body, forming long-term immune memory and preventing cancer recurrence and metastasis. In addition, they mature dendritic cells whose function has been impaired by cancer, improving the immunosuppressed state.

The main difference between NK cells and NKT cells is that NK cells belong to innate immunity and directly attack cancer cells and other pathogens in an MHC-independent manner, while NKT cells possess the properties of both T cells and NK cells, recognizing lipid antigens via MHC molecules (CD1d) and performing both potent immunomodulation (cytokine production) and direct attack. The differences are shown in the table below.

Difference between NK cell and NKT cell therapy

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