作用機制 Mechanism of Action
從1996年起至今，已有超過一百個關於AVEMAR的完整研究，包含許多科學家的投入，以及涵蓋細胞株、動物實驗、到臨床研究等方法。已發表的研究顯示飲用AVEMAR所得到的廣泛功效，是來自於數種非常不同的作用機制。AVEMAR這些引人注目的結果也有可能部份發生，因為AVEMAR單獨作用在至少數種不同的癌症機制，可能有部分機制也能減輕其他疾病的症狀，例如全身性紅斑性狼瘡及類風濕性關節炎。
其主要作用機制包括：
- 限制癌細胞生長及增生所需的醣類來源
由於癌細胞是透過與正常細胞不同的代謝途徑來獲得快速生長所需的大量醣類，所以AVEMAR能作用在專一代謝途徑上以減緩癌細胞增生而不影響正常細胞。
- 在腫瘤細胞內引發細胞凋亡
AVEMAR可能透過以下機制，使癌細胞進行自殺性凋亡：
- 酪胺酸磷酸化及細胞外鈣離子湧入
- 藉由凋亡酵素caspase參與之PARP蛋白切割，加速癌細胞自殺
- AVEMAR藉由減少核糖核甘酸脢(ribonucleotide reductase, RR)的活性，以抑制新DNA合成
- AVEMAR非特定選擇性抑制環氧脢(COX)的活性
- 調節免疫系統
- AVEMAR明顯增加母細胞轉型程度
- AVEMAR具免疫回復功效
- AVEMAR能影響Th1/Th2細胞素交互作用及自體抗體生成
- 降低第一型MHC組織表面抗原在腫瘤型T及B細胞株表面的表現量
- 調節骨髓細胞製造細胞素增進內皮細胞合成細胞附著分
More than 100 comprehensive researches have been carried out on Avemar since 1996, involving dozens of researchers and progressing methodically from cell line to animal studies and to human studies. Published studies have shown that the wide range of beneficial effects of Avemar administration result from a number of very different mechanisms of action. Avemar’s dramatic results may occur partly because it works through at least several different mechanisms in cancer alone, some of which may also ameliorate symptoms of other diseases, such as systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA).
Avemar restricts glucose cancer cells need for growth & proliferation
Avemar’s most unique effect – restricting cancer cells’ access to the large amounts of glucose they need to grow and divide rapidly – may be its most important benefit. Today, some of the most effective cancer therapies are those that affect various specific targets of gene, cell signaling and enzyme function. However, there are thousands of such targets, many specific only to a particular type of cancer. As a result, most targeted therapies have limited effect because they affect so few cancers. But inhibiting cancer cells’ access to glucose is a much more significant target, because virtually every cancer cell type utilizes glucose at rates from 10 to 50 times higher than normal,healthy cells do – a key characteristic of cancer cells, called the Warburg effect, named for Dr. Otto Warburg, whose experiments in the 1920s first revealed it.
Cancer cells need such large amounts of glucose to support the rapid growth and fast cell division (proliferation). They use glucose to make ribose, which forms the backbone of RNA and DNA cells must make to divide. Large amounts of ribose can’t be made quickly by using oxygen as normal cells do, so cancer cells turn to a non-oxidative process known as the transketolase pathway or pentose phosphate pathway (Boros et al. 2002a; Boros et al. 2002b; Cascante et al. 2002). Boros et al. (2001) and Comin-Anduix et al. (2002) showed that Avemar inhibit transketolase and thereby inhibit carbon flow in the non-oxidative pathway, slowing cancer cell growth and proliferation. Utilized more slowly, glucose is synthesized through an oxidative pathway into cell substances and structures supportive of differentiation, instead. In various cancer cell lines tested, the more glucose utilization, the greater the metastatic potential, and the more dramatic Avemar’s effects have been but Avemar doesn’t effect normal cells until dosage is 50 times higher than that recommended for use. (Comin-Anduix et al. 2002)
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Avemar triggers apoptosis in tumor cell lines
One of Avemar’s most important mechanisms of action is its support of apoptosis, or programmed cell death, through which cells with DNA too damaged to repair (a hallmark of cancer cells) are forced to self-destruct. At 1 mg/ml, Avemar induces apoptosis in B and T tumor cell lines but not in peripheral mononuclear cells (Fajka-Boja et al., 2002). In the dose response study, Comin-Anduix et al. (2002) showed that the cytotoxic IC50 concentration of Avemar for Jurkat tumor cells is 0.2 mg/ml (72 h incubation). It requires 50-fold higher IC50 (10.2 mg/ml) for the peripheral blood lymphocytes to induce the same apoptotic response, which provides a broad therapeutic window for cancer treatment. Several possible mechanisms have been studied on the apoptotic effect of Avemar.
Tyrosine phosphorylation and extracellular Ca2+ influx
Avemar triggers tyrosine phosphorylation of several intracellular proteins of T and B cell lines, the pattern of protein phosphorylation was different from that normally induced by T cell and B cell receptors. The stimulation of Avemar also resulted in elevation of the intracellular Ca2+ concentration by influx of the extracellular Ca2+. These data suggested that tyrosine phosphorylation of unidentified intracellular substrate(s) plays a role in the Avemar-induced apoptosis (Fajka-Boja et al., 2002).
Avemar increases cancer cell suicide by caspase-mediated PARP cleavage
Avemar induced the phosphotidylserine externalization, which is a fundamental characteristic of apoptosis. The process can be inhibited specifically by caspase inhibitors suggested the involvement of caspases in mediating the biological apoptosis-inducing effects of Avemar. Furthermore, Avemar induced proteolytic cleavage of poly (ADP-ribose) polymerase (PARP), which is considered to be a hallmark of activation of capases-3 like proteases during apoptosis (Comin-Anduix et al., 2002). Cells use PARP to repair any damaged DNA before they divide. Cancer cells need large quantities of PARP for DNA repair because the increase of cell division cause higher instances of gene mutation. With PARP proteolytic cleavaged by Avemar, many cancer cells are forced into apoptosis and die. The aim of many cancer therapies, including radiation, chemotherapy, and some herbal therapies, is to trigger apoptosis in cancer cells by damaging their DNA, so reducing DNA-repairing PARP levels can make these therapies more effective at lower intensities.
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Avemar inhibits de novo DNA synthesis by down-regulation of ribonucleotide reductase activity
Ribonucleotide reductase (RR) is responsible for the conversion of ribonucleotides to deoxyribonucleotide triphosphates, which are precursors of DNA synthesis. RR was demonstrated to be significantly up-regulated in tumor cells to meet the increased need for dNTPs of these rapidly proliferating cells for DNA synthesis. The enzyme was therefore indicated as being an excellent target for cancer chemotherapy, and various inhibitors of RR have entered clinical practice or are under preclinical or clinical development. Illmer et al. (2005) showed that in situ RR activity of HT-29 colon carcinoma cell lines can be inhibited by Avemar in a concentration-dependent manner. These results were then confirmed by the significant decrease of dNTP pool size after the incubation of HT-29 cells with Avemar.
Avemar non-selectively inhibit the activity of COX enzyme
Cyclooxygenases (COX-1 and COX-2) are enzymes responsible for the production of inflammation mediators. Aspirin is the first and most wildly used inhibitor of COX activities. The class of COX-2 inhibitors of non-steroid anti-inflammatory drugs (NSAID) has been shown effects for the treatment of rheumatoid arthritis. The inhibition of COX-2 is responsible for the anti-inflammatory and anti-cancer effects of COX inhibitors, whereas the inhibition of COX-1 is responsible for the side effects of aspirin and other non-steroidal anti-inflammatory drugs.
It has been demonstrated that the inhibition of COX causes a decrease of incidences of cancers such as colon cancer or breast cancer. Illmer et al. (2005) incubated COX-1 and COX-2 enzymes with increasing concentration of Avemar. Their results demonstrated Avemar non-selectively inhibited COX enzyme activities. As inhibition of COX enzymes is also generally considered a preventive tool in colorectal cancer, these results may also shed light on the mechanism of the chemopreventive activity of Avemar against carcinogenic chemically induced experimental colon cancer (Zalatnai et al. 2001) and the impressive antitumor effects observed with Avemar in patients suffering from colon carcinoma. (Jakab et al. 2003)
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Avemar modulates immune system
Avemar significantly increases the degree of blast transformation
C57B1/6 mice were treated orally, via gastric tube with 0.1 ml of Avemar, five times a week for 6 weeks. The splenic cells were cultured and stimulated by Concanavalin A. The blast transformation was measured by 3H-thymidin incorporation into the cells. The results showed that the pre-treatment of Avemar in mice increase the blast transformation inducing effect of Concanavalin A on peripheral T lymphocytes. (Hidvégi et al., 1999)
Avemar has immune restorative effect
C57/B1 mice were given skin transplants from the coisogenic mice strain B10/LP, which normally could be expected to be tolerated for 16–25 days before rejection. Thymectomized control (untreated) mice rejected the transplants at a gender mean of 52 (male) or 41 (female) days. Thymectomized mice treated with Avemar rejected the grafts at a mean of 29 days (male) or 33 days (female). Control (untreated) mice not thymectomized rejected the transplants at a gender mean of 21 or 29 days. These results, with immune function of mice seriously immunocompromised by thymectomy restored to near that of non-thymectomized mice (untreated), demonstrate the very significant immune restorative effects of Avemar treatment in these animals. (Hidvégi et al., 1999)
Avemar can effect Th1/Th2 cytokine network and autoantibody production
Systemic lupus erythematosus (SLE) can be induced in naïve mice by idiotypic immunization with autoantibodies, e.g. anti-dsDNA. The idiotypically induced model showed an upregulation of Th1 cytokines (IL-2, IFNγ) production at early stage of the disease, while the increase in the Th2 cytokines (IL-4, IL-10) expression was ascendant as the autoimmune status progress. Amelioration of the clinical manifestation of the disease was achieved by immunomodulation of the cytokine profile via reversing the Th2 response to Th1. (Ehrenfeld, et al., 2001)
Oral administration of Avemar to lupus mice resulted in 42-56% decrease of autoantibody comparing to untreated control. In vitro production of IL-2, IFNγ, IL-4 and IL-10 by splenocytes derived from experimentally induced mice treated with Avemar showed that non-significant change in the production of IL-2 and IFNγ production, and a pronounced decrease in the production of IL-4 and IL-10. From this data, it could be concluded that treatment of Avemar can affect the Th1/Th2 network by inhibiting the Th2 response thus decreasing the autoimmune disease SLE. (Ehrenfeld, et al., 2001)
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Avemar decrease the MHC class 1 protein level on the surface of tumor T and B cell lines
A way for tumors to survive in the host environment is to evade the defense control of the host by mimicking themselves as normal cells for the survey of the immune system. Natural Killer (NK) cells, which play an important role in anti-tumor defense, recognize and are blocked by the expression of major histocompatibility complex class I (MHC-I) molecules on their target cells. Consequently, tumor cells develop an effective camouflage by expressing high levels of MHC-I to avoid NK surveillance. Avemar has been shown to suppress the display of MHC-1 on the surface of cancer cells, thus increasing NK cell targeting and cancer cell death. (Fajka-Boja et al., 2002)
Effect of Avemar on the cytokine production of myeloid cells
Tumor necrosis factor-alpha (TNF) first identified as a serum factor from lipopolysaccharide-treated mice, induced hemorrhagic necrosis in tumors. In the human body, TNF is mainly produced by activated macrophages and epithelial cells. TNF is a major mediator of apoptosis, inflammation, and immunity. It is important in the natural defense against cancer. Higher concentration of Avemar proved to be toxic to certain myeloid cells. In the lower concentration range, Avemar unregulated TNF synthesis in a dose dependent manner. The effect of Avemar proved to be specific for myeloid cells. Unlike myeloid cells, lymphoid cells (virus-immortalized and leukemic B cell) were not greatly influenced by the presence of Avemar. (Telekes et al., 2005)
The effect of Avemar on the myeloid cells was not restricted to the increased production of TNF. Up regulated expression of a number of cytokine genes (TNF, IL-4, IL-5, IL1-α, IFN-γ, IL-2, IL-6, IL-1β, IL-3) in myeloid cells have been studied using RNase protection assay. Avemar treatment unregulated the production of mRNAs of IL1-α, IL-2, IL-5 and IL-6 by 3.7-, 6-, 8.4-, 4.5-fold in RAW246.7 mouse myeloid leukemic cell lines. (Telekes et al., 2005)
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Avemar upregulated the synthesis of cell adhesion molecules on endothelial cells
Endothelial cells in the vasculature of human solid tumors have decreased expression of intercellular adhesion molecule-1 (ICAM-1) compared to normal endothelial cells. Incubation of tumor-derived endothelial cells with TNF resulted in the expression levels of only 20%, achieved in similarly treated normal tissue-derived endothelial cells because tumor angiogenesis induces anergy in endothelial cells. This phenomenon may serve as a tumor-protecting mechanism because leukocytes require ICAM-1 to leave the vascular system to infiltrate the tumor tissue. The expression of ICAM-1 and VCAM-1 on the surface of CDC-HMEC microvascular endothelial cell line has been studied by flow cytometry using monoclonal antibodies. Avemar induced the production of ICAM-1 and synergized the effect of TNF. VCAM-1 expression or TNF-mediated induction of VCAM-1, however, was not influenced by the presence of Avemar. (Telekes et al., 2005)
Effect of Avemar on the cytokine production of myeloid cells
Tumor necrosis factor-alpha (TNF) first identified as a serum factor from lipopolysaccharide-treated mice, induced hemorrhagic necrosis in tumors. In the human body, TNF is mainly produced by activated macrophages and epithelial cells. TNF is a major mediator of apoptosis, inflammation, and immunity. It is important in the natural defense against cancer. Higher concentration of Avemar proved to be toxic to certain myeloid cells. In the lower concentration range, Avemar unregulated TNF synthesis in a dose dependent manner. The effect of Avemar proved to be specific for myeloid cells. Unlike myeloid cells, lymphoid cells (virus-immortalized and leukemic B cell) were not greatly influenced by the presence of Avemar. (Telekes et al., 2005)
The effect of Avemar on the myeloid cells was not restricted to the increased production of TNF. Up regulated expression of a number of cytokine genes (TNF, IL-4, IL-5, IL1-α, IFN-γ, IL-2, IL-6, IL-1β, IL-3) in myeloid cells have been studied using RNase protection assay. Avemar treatment unregulated the production of mRNAs of IL1-α, IL-2, IL-5 and IL-6 by 3.7-, 6-, 8.4-, 4.5-fold in RAW246.7 mouse myeloid leukemic cell lines. (Telekes et al., 2005)
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Avemar upregulated the synthesis of cell adhesion molecules on endothelial cells
Endothelial cells in the vasculature of human solid tumors have decreased expression of intercellular adhesion molecule-1 (ICAM-1) compared to normal endothelial cells. Incubation of tumor-derived endothelial cells with TNF resulted in the expression levels of only 20%, achieved in similarly treated normal tissue-derived endothelial cells because tumor angiogenesis induces anergy in endothelial cells. This phenomenon may serve as a tumor-protecting mechanism because leukocytes require ICAM-1 to leave the vascular system to infiltrate the tumor tissue. The expression of ICAM-1 and VCAM-1 on the surface of CDC-HMEC microvascular endothelial cell line has been studied by flow cytometry using monoclonal antibodies. Avemar induced the production of ICAM-1 and synergized the effect of TNF. VCAM-1 expression or TNF-mediated induction of VCAM-1, however, was not influenced by the presence of Avemar. (Telekes et al., 2005)
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