What Are the Different Types of Immunotherapy for Prostate Cancer?

Under normal circumstances, the immune system can recognize and clear tumor cells in the tumor microenvironment. However, in order to survive and grow, tumor cells can use different strategies to suppress the body's immune system and cannot kill tumor cells normally, thus preventing tumors. Stages of the immune response survive. ^[1-2] The above characteristics of tumor cells are called immune escape. In order to better understand the complexity of multi-step and multi-step of tumor immunity, Chen He proposed the concept of tumor-immune cycle. The tumor-immune cycle is divided into the following seven steps: 1. tumor antigen release; 2. tumor antigen presentation; 3. activation and activation of effector T cells; 4. migration of T cells to tumor tissue; 5. infiltration of T cells in tumor tissue; 6. T cells recognize tumor cells; 7. Clear tumor cells. Any abnormality in these links can lead to the failure of the anti-tumor-immune cycle and immune escape. Different tumors can suppress immune cells' effective recognition and killing of tumor cells through abnormal abnormalities in different links, which can produce immune tolerance and even promote the occurrence and development of tumors.

Under normal circumstances, the immune system can recognize and clear tumor cells in the tumor microenvironment. However, in order to survive and grow, tumor cells can use different strategies to suppress the body's immune system and cannot kill tumor cells normally, thus preventing tumors. Stages of the immune response survive. ^[1-2] The above characteristics of tumor cells are called immune escape. In order to better understand the complexity of multi-step and multi-step of tumor immunity, Chen He proposed the concept of tumor-immune cycle. The tumor-immune cycle is divided into the following seven steps: 1. tumor antigen release; 2. tumor antigen presentation; 3. activation and activation of effector T cells; 4. migration of T cells to tumor tissue; 5. infiltration of T cells in tumor tissue; 6. T cells recognize tumor cells; 7. Clear tumor cells. Any abnormality in these links can lead to the failure of the anti-tumor-immune cycle and immune escape. Different tumors can suppress immune cells' effective recognition and killing of tumor cells through abnormal abnormalities in different links, which can produce immune tolerance and even promote the occurrence and development of tumors.

Tumor immunotherapy is a treatment method that controls and clears the tumor by restarting and maintaining the tumor-immune cycle and restoring the body's normal anti-tumor immune response. Including monoclonal antibody-type immune checkpoint inhibitors, therapeutic antibodies, cancer vaccines, cell therapy, and small molecule inhibitors. In recent years, the good news of tumor immunotherapy has continued. At present, it has shown strong antitumor activity in the treatment of various tumors such as melanoma, non-small cell lung cancer, kidney cancer and prostate cancer. Immunotherapy drugs have been approved for clinical use by the Food and Drug Administration (FDA). Tumor immunotherapy was named the most important scientific breakthrough of the year by Science Magazine in 2013 due to its excellent efficacy and innovation ^[3] .

Chinese name

Tumor immunotherapy

Foreign name

Tumor immunotherapy

Classification of tumor immunotherapy

(1) Monoclonal antibody checkpoint inhibitor ( immune checkpoint inhibitor ) inhibitor

1. PD-1 / PD-L1 pathway and PD-1 / PD-L1 inhibitor

Anti-programmed death protein 1 (PD-1) antibody is currently the most studied and clinically developed immunotherapy. PD-1 acts in the effector phase of the immune response. It is expressed on activated T cells, B cells, and myeloid cells. It has two ligands, namely programmed death ligand 1, PD. -L1) and PD-L2. PD-L1 / L2 is expressed in antigen-presenting cells, and PD-L1 is also expressed in a variety of tissues. The combination of PD-1 and PD-L1 mediates co-suppression signals of T cell activation, suppresses the killing function of T cells, and plays a negative regulatory role in the human immune response. The Chinese scientist Zhanping Lab first discovered that PD-L1 is highly expressed in tumor tissues and regulates the function of tumor-infiltrating CD8 + T cells. Therefore, immunoregulation targeting PD-1 / PD-L1 as a target has important significance in the fight against tumors. ^[4]

PD-1 / PD-L1 inhibitors can specifically bind to PD-L1 on tumor cells to inhibit its expression, so that the inhibited T cells can restore the recognition function of tumor cells, thus achieving the autoimmune system Achieve anti-cancer effect.

In recent years, a variety of PD-1 / PD-L1 monoclonal antibodies have been rapidly developed in clinical research of tumor immunotherapy. Currently PD-1 inhibitors Pembrolizumab and Nivolumab have been approved by the FDA for advanced melanoma, non-small cell lung cancer, Hodgkin's lymphoma, and head and neck squamous cell carcinoma. Nivolumab has also been approved by the FDA for the treatment of kidney cancer and urothelial cancer. Wait. In addition, monoclonal antibodies such as PD-L1 inhibitors Atezolizumab and Durvalumab have also entered multiple phase III clinical studies covering non-small cell lung cancer, melanoma, and bladder cancer.

2. CTLA-4 inhibitor

Cytotoxic T-lymphocyte antigen 4, CTLA-4 is a transmembrane protein expressed on the surface of activated T cells. CTLA-4 acts on the initiation phase of the immune response, and its activation can suppress the initiation of T cell immune response, which results in the reduction of activated T cells and prevents the generation of memory T cells. Studies have found that tumor cells can activate CTLA-4, inactivating activated T cells, thereby achieving the immune escape of the tumor itself. ^[5-6]

Several pre-clinical studies have found that blocking CTLA-4 can restore T cell activity and prolong the survival time of memory T cells, thereby restoring the body's immune function to tumor cells and increasing the rate of tumor control. Anti-CTLA-4 specific monoclonal antibody. ^[7-8]

At present, two CTLA-4 inhibitors, Ipilimumab, have been approved by the FDA for adjuvant treatment of stage III melanoma and advanced melanoma. ^[9] Clinical studies of Ipilimumab and Tremelimumab in kidney cancer, prostate cancer, lung cancer, etc. have been widely developed. Carry out. Early clinical studies have shown that both monoclonal antibodies are safe and effective, both as single agents or in combination with IL-2, PD-1 / PD-L1 inhibitors, or chemotherapy.

3. Other types of monoclonal antibodies

Other monoclonal antibodies, such as OX40 and 4-1BB monoclonal antibodies that enhance the second signal of T cells to promote tumor-specific T cell activation and proliferation, are still under development.

4. Common adverse reactions and management of immune checkpoint inhibitors

Because immune checkpoint inhibitor therapy uses the body's own immune system to kill tumors, ^[10] can release the suppressive state of the immune system. Therefore, adverse events related to immune checkpoint inhibitors include almost all organs. Such as skin (papular papules, vitiligo, psoriasis, Lyell syndrome, delayed hypersensitivity of multiple organs related to drugs), gastrointestinal tract (small bowel colitis, gastritis, pancreatitis, celiac disease), endocrine organs (thyroid function Hyperactivity or reduction, pituitary inflammation, adrenal insufficiency, diabetes mellitus), lungs (immune pneumonia, pleurisy, pulmonary sarcoma), peripheral and central nervous system (peripheral neuropathy, aseptic meningitis, Guillain-Barre syndrome, neurons Lesions, myelitis, meningoencephalitis, myasthenia gravis, liver (immune hepatitis), kidneys (interstitial nephritis, lupus glomerulonephritis) blood system (hemolytic anemia, thrombocytopenia, granulocytopenia, Three-line reduction syndrome), musculoskeletal system (arthritis, myopathy), heart (pericarditis, myocarditis), eyes (uveitis, conjunctivitis, retinitis, choroiditis, eyelid inflammation, periorbital myositis), etc. The severity of the toxic events is not the same. Some symptoms are mild and easy to manage, while others are severe and can be life-threatening. ^[11-13] The overall incidence of immune-related adverse reactions is lower than that of chemotherapy and is well tolerated. The most common adverse reactions to treatment are fatigue, decreased appetite, nausea, weakness, and rash. The overall serious adverse reactions ( Grade 3/4 adverse reactions) have an incidence of 7-13%. ^[14-17] Most adverse reactions are reversible and manageable. During the course of immunotherapy, prevention, evaluation, inspection, treatment and monitoring of immune-related adverse reactions should be done, and treatment-related adverse reactions should be found in time, the dosage of medication should be adjusted and corticosteroids should be used for corresponding treatment.

(1) Prevention of high-risk groups: individual or family history of autoimmune disease; diffuse tumor invasion, such as cancerous lymphangiitis, tumor infiltration with surrounding inflammation; opportunistic infection, chronic infection, etc., have caused T cell depletion and apoptosis ; Certain drugs such as antiarrhythmics, antihypertensives, antibiotics, antispasmodics, or antipsychotics are themselves associated with autoimmune diseases.

(2) Examination: The symptoms often associated with immunotoxicity include skin symptoms, gastrointestinal symptoms, and endocrine symptoms. In addition, it includes neurological symptoms, respiratory symptoms, rheumatic symptoms, liver disease symptoms, hematological symptoms, kidney disease symptoms, cardiovascular symptoms, and ophthalmic symptoms. Immune abnormalities can occur at any time. According to the median time to onset, immunotoxicity can be divided into early (<2 months) and late (> 2 months) toxicity. Early toxicity includes skin (5 weeks), gastrointestinal (7.3 weeks), and liver (7.7 weeks), while late toxicity includes lungs (8.9 weeks), endocrine (week 10.4), and kidneys (15.1 weeks). Some immunodeficiency toxicities will be delayed, and some will not occur even after 1 year of immunotherapy.

(3) Treatment: A side effect of enhancing the immune response of T cells is the potential occurrence of autoimmune inflammation in normal tissues. In most cases, these side effects can be controlled with immunomodulatory drugs. The best drugs to combat these inflammatory reactions, especially when they reach a severe stage, are hormones. For patients who are unsatisfactory with hormone therapy, other immunomodulatory drugs can also be selected, such as anti-TNF- antibody infliximab, mycophenolate, tallimus, and cyclosporine. T cell depletion drugs such as anti-human thymocyte globulin have also been reported to be effective in rare cases.

If adverse reactions related to immune checkpoint inhibitors occur, please contact medical staff in time.

(Two) therapeutic antibodies

Therapeutic antibodies are synthetic antibodies designed to destroy tumor cells in the laboratory. They try to kill tumor cells through different ways, including antibody-dependent cell-mediated cytotoxity (ADCC), complement-dependent Cytotoxicity (complement-dependent cytotoxity, CDC) and antibodies directly induce apoptosis. . A number of therapeutic antibodies have been approved for clinical treatment of tumors. In 1997, the first chimeric antibody against CD20, Rituximab (Mirova), was approved by the US FDA for use in the treatment of non-Hodgkin's lymphoma. In 1998, the first humanized anti-Her2 monoclonal antibody, Trastuzumab (Herceptin), was launched for the treatment of breast cancer. In 2006, Panitumumab, the first human antibody against epidermal growth factor, was approved to treat colorectal cancer. And in 2011, the FDA approved a new generation of antibody-drug conjugates (ADCs), Adcetris, which consists of the anti-CD30 chimeric antibodies Brentuximab and monomethylstatin Oliss Statin E (Auristain E), for the treatment of lymphoma.

(Three) cancer vaccine

Cancer vaccine refers to the introduction of tumor antigens in various forms, such as tumor cells, tumor-related proteins or peptides, genes expressing tumor antigens, etc., to overcome the immunosuppressive state caused by tumors and activate the patient's own immune system to achieve Treatments for the purpose of controlling or clearing the tumor. Cancer vaccines can be divided into preventive vaccines and therapeutic vaccines. Prophylactic vaccines, such as the cervical cancer vaccine, can effectively prevent certain carcinogenic HPV-related cervical diseases. ^{[18] The} first tumor therapeutic vaccine, Sipuleucel-T vaccine (Provenge), was approved by the US FDA for the treatment of prostate cancer on April 29, 2010.

(D) Cell therapy

Without external intervention, the number of T cells that can recognize tumor cells in the human body is very small, accounting for less than one in 100,000. Cell therapy, also called adoptive T cell transfer (ACT), is an attempt to make ordinary T cells become T cells that can recognize tumor cells through external modifications, thereby triggering immune effects on tumor cells.

Adoptive cellular immunotherapy, in accordance with its development process, is in turn lymphokine-activated killer (LAK), tumor infil-trating lymphocytes (TIL), and natural killer cell. NK), cytokine-induced killer (CIK), cytotoxicT lymphocyte (CTL), and genetically modified T cells (CAR-T, TCR-T).

(1) Tumor infiltrating lymphocytes (TIL) are lymphocytes isolated from tumor sites and are produced after expansion in vitro by cytokines such as IL-2. Their phenotypes are mainly CD4T cells and CD8T cells, which have a certain Tumor-specific and MHC-restricted. Although TIL has shown strong cell proliferation and killing effects in melanoma, similar efficacy has not appeared in other tumors.

(2) NK cell immunotherapy related antibodies have been used in the treatment of melanoma, lung cancer and kidney cancer. NK cells belong to the innate immune system. Unlike T cells, they do not require tumor-specific recognition or clonal expansion before exerting anti-tumor effects. The antitumor effect of NK cells is controlled by a large number of receptors on the cell surface.

(3) CIK cells are NK-like T cells derived from peripheral blood mononuclear cells induced by in vitro differentiation of anti-CD3 monoclonal antibodies and cytokines such as IL-2, IFN-y, and IL-1, showing a phenotype of CD3 and CD56. It has both non-MHC-restrictive characteristics and T-lymphocyte antitumor activity.

(4) CTL cells are the main effector cells of body-specific anti-tumor immunity. The preparation process is: isolation of tumor cells; modulation of tumor cells: introduction of B7 gene into tumor cells by direct introduction method or reverse transcriptase-mediated transfer method And detect the expression of B7 molecules in tumor cells; induce CTL: co-culture tumor cells with effector cells after modulation and modification to induce highly active CTL; isolate CTL cells for clinical treatment.

(5) The latest CAR-T treatment method: immunologists collect T cells from the patient's own blood, and then genetically process the T cells after collection to express a special receptor capable of recognizing specific tumor antigens on the surface. The receptor is called a chimeric antigen receptor (CAR). At the same time, a signaling region that causes T cell activation is added to the intracellular segment of the receptor. CAR is a protein receptor that allows T cells to recognize specific proteins (antigens) on the surface of tumor cells. T cells that express CAR can recognize and bind to tumor antigens and then attack tumor cells. This CAR-expressing T cell is called CAR-T. The designed CAR-T cells can be cultured and grown in the laboratory, reaching billions of times. The expanded CAR-T cells are injected into the patient. The injected T cells will also proliferate in the patient and kill Tumor cells with corresponding specific antigens. ^[19] CAR-T cell therapy has shown good targeting, lethality and durability in clinical trials, providing a new solution for immune cell therapy, showing great development potential and application prospects. Kymriah (Tisagenlecleucel, CTL-019), a CAR-T cell drug currently approved by the US FDA, is used to treat acute lymphoblastic leukemia (ALL) in children and young adults (2-25 years old). And Yescarta (AxicabtageneCiloleucel, KTE-C10), is used to treat certain types of adult large B-cell lymphoma patients who have failed other therapies or have relapsed after receiving at least 2 regimens. So far this approach has been limited to small-scale clinical trials. These engineered immune cells have yielded some significant results in treating patients with advanced hematological tumors, and are being tried for solid tumors. Although these preliminary results are encouraging, there are many aspects of CAR-T cell therapy to be studied, such as unique side effects, cytokine release syndrome, etc.

(6) TCR-T cell therapy, like CAR-T therapy, is also used to improve the ability of T cell receptors to recognize and attack specific cancer cell antigens through genetic modification. The principle of TCR-T is to treat patients' tumors Among infiltrating lymphocytes (tumor-infiltrating lymphocytes, TILs), T cells that can kill tumors can be identified by restricting antigens, and their T cell receptor (TCR) sequences are obtained by gene cloning technology. This gene was transfected into more T cells, which caused the T cells that recognized the antigen to grow tens of thousands. TCR-T is derived from TCR, so it can recognize various antigens derived from the nucleus, cytoplasm and membrane. A number of related researches are currently underway, and some research results have good prospects.

(5) Small molecule inhibitors

There are many immunosuppressive molecules in the tumor microenvironment. Immunotherapy strategies to improve the tumor immune microenvironment by regulating the functions of these inhibitory molecules have also received attention. Indoleamine- (2,3) -dioxygenase (IDO), IDO expressed in tumors mediates tumor immune escape. Antigen-presenting cells such as macrophages and IDOs on dendritic cells can induce T-cell immune tolerance to tumor antigens by inhibiting T-cell proliferation. ^[20] Therefore, IDO inhibitors can regulate the tryptophan content of the tumor microenvironment, prevent the inhibition of T cell proliferation in the tumor microenvironment, and become a potential target for immunotherapy. Multiple phase I / II clinical studies have confirmed that IDO inhibitors can improve the efficacy of PD-1 / PD-L1 inhibitors.

(6) Immune system regulators

Immune system modulators are the earliest method used for tumor immunotherapy. They are often called active nonspecific immunotherapy. They can be traced back to William Coley's use of Streptococcus culture in 1892. To treat sarcoma. Immune system modulators include cytokine therapy (IL-2, INF), synthetic molecules, immune adjuvants (BCG), and short peptides (thymosin) that have been developed subsequently. Recently, some scholars have used malaria to treat tumors. In fact, they have also used the inflammatory response and non-specific immune effects activated by Plasmodium. However, the effective rate of immune system modulators is only 10%, and it is mainly used for some solid tumors, including metastatic kidney cancer and malignant melanoma. In the future, it is worth exploring the direction of combining non-specific and specific immunotherapy or using different immune system modulators.

Tumor immunotherapy tumor biomarkers

1. Definition of tumor biomarkers

At present, it is still controversial how to define tumor biomarkers. The National Cancer Institute (NCI) defines biomarkers as "biomolecules found in blood, other body fluids or tissues, which can be used as a sign of abnormal processes or diseases. Biomarkers can also be used to determine the body's response to treatment. Biomarkers may also be called molecular markers or molecular markers. " ^[21] We can consider that tumor biomarkers are biomolecules that can be used as a sign of tumors or to judge the response to tumor treatment, that is, we can use tumor biomarkers to help diagnose tumors, determine the choice of treatment options, and predict the efficacy of treatment.

2. The role of tumor biomarkers

The role of tumor biomarkers runs through the entire process of tumor diagnosis and treatment, from tumor risk prediction and diagnosis to treatment plan selection and efficacy prediction. More importantly, the discovery and application of tumor biomarkers makes it possible for targeted therapy and immunotherapy and effectively improve the efficacy.

(1) Tumor risk prediction

Some biomarkers that can be used to predict high-risk tumors have been found. For example, patients with positive mutations in the BRCA1 / 2 gene have a higher risk of breast cancer and ovarian cancer. ^{[twenty two]}

(2) Cancer diagnosis

Although the gold standard for tumor diagnosis is still pathological examination, tumor biomarker-assisted diagnosis has gradually become popular due to its convenience and non-invasiveness.

(3) Prognosis and treatment prediction

With the gradual maturity of targeted therapy and immunotherapy methods, tumor biomarkers have shown considerable potential in treatment and prognosis prediction. For example, the higher the expression of PD-L1 for certain cancer species, the better the efficacy. But for some tumors, the expression of PD-L1 cannot predict the efficacy, and better biomarkers still need to be explored. ^{[23] [24]} Nonetheless, the clinical evidence currently available is sufficient to prove the potential of biomarkers in predicting curative effects. Testing of relevant biomarkers before treatment can help better achieve precise treatment and select the most appropriate Suitable treatment options.

(4) Predict or monitor tumor recurrence

Biomarkers can also be used to predict or monitor tumor recurrence. Currently there are more mature applications in the field of breast cancer, which can be used to predict the risk of breast cancer recurrence within 10 years. ^[25]

3. Common tumor biomarkers in immunotherapy

The common or potential biomarkers in immunotherapy are mainly related to the following mechanisms: 1) tumor antigens, which can prompt high-frequency mutations and new antigen biomarkers, such as tumor mutation load (TMB), high microsatellite instability ( MSI-H), etc .; 2) Inflammatory tumor microenvironment, which can indicate biomarkers of inflammatory phenotype, such as PD-L1, inflammatory characteristics, etc .; 3) Tumor immunosuppression, except PD-1 / CTLA-4 Other biomarkers that can clarify tumor immune escape, such as Tregs, MDSCs, IDO, LAG-3, etc .; 4) host environment; 5) intestinal microorganisms, biomarkers that can prompt the characteristics of the host environment.

(1) PD-L1

PD-L1 is a cell surface protein that interacts with PD-1 receptors on the surface of activated T and B cells to inactivate T cells and no longer attack tumor cells. Clinical trials have found that high tumor expression of PD-L1 is associated with increased tumor aggressiveness and a 4.5-fold increased risk of death. ^[26] Among patients with non-squamous lung cancer, PD-1 / PD-L1 is used in patients with high PD-L1 expression. Inhibitors are more effective. ^{[23] [24]}

(2) Tumor mutation load (TMB)

Tumor mutation burden (TMB) refers to the total number of substitution and insertion / deletion mutations per megabase in the exon coding region of the gene being evaluated in a tumor specimen. High TMB tumor cells may have more new antigens, resulting in a corresponding increase in tumor microenvironment and peripheral anti-tumor T cells. Therefore, it is speculated that patients with high TMB are more likely to respond to tumor immunotherapy. ^[27] However, it is worth noting that the expression level of TMB varies among different cancer species, and the overall TMB level of some tumor patients will be higher.

(3) Mismatch Repair (MMR)

Mimatch repair (MMR) refers to an enzyme that corrects DNA mismatches produced during DNA replication to prevent mutations in dividing cells from becoming permanent mutations. This process involves four key genes, MLH1, MSH2, and MLH6. And PMS2. In the process of mismatch repair, a certain MMR protein may be missing in some cases, resulting in failure to detect errors. This situation is called mismatch repair loss (dMMR). ^[28] Sometimes MMR abnormalities can trigger a series of cancerous phenotypes. Clinical studies have found that mutations in the MMR gene may help accurately predict the response of patients with PD-1 inhibitors. ^[29]

(4) Microsatellite instability (MSI)

Microsatellite is a tandem repeat DNA sequence found in the human genome, such as ATATATAT, CTCTCTCT, GGGG or AAAA. ^[30] Microsatellite instability is a molecular phenotype caused by high-frequency mutations in the genome. It is caused by mutations in the microsatellite region that cannot be repaired after the mismatch repair system is damaged. ^[29] High microsatellite instability (MSI-H) means that at least two of the five microsatellite markers of a tumor are unstable; only one marker is classified as low-level microsatellite instability (MSI-L); microsatellite stable (MSS) without labile markers. ^[31] Clinical trials have found that patients with MSI-H respond better to immunotherapy. ^[32]

(5) Intestinal microbiome

Recently, the relationship between the gut microbiota and immunotherapy has been closely watched. One study showed that ^{[33] the} intestinal flora can modulate the response to anti-melanoma immunotherapy. "Beneficial" intestinal microbiome (such as high diversity and rich Ruminococcaceae / Faecalibacterium) will enhance antigen presentation, improve T cell function and tumor microenvironment to enhance anti-tumor immune response. And "unfavorable" intestinal flora (such as low diversity and rich in Bacteroidales) can disrupt the antitumor response. It is suggested that the intestinal flora should be evaluated when receiving immune checkpoint inhibitor therapy. Studies have also suggested that the use of antibiotics may weaken the effectiveness of immunotherapy due to the effect on intestinal microorganisms, but the conclusion needs further evidence to support.