Cancer biology is yet to be fully understood. Cellular mutation may occur as a result of free radical damage (with activation of oncogenes or suppression of tumor suppressor genes) and genetic susceptibility and toxicity (e.g., hepatopathogenic toxins). In traditional herbal medicine, cancer is nearly always viewed as a sign of systemic toxicity. However, immune dysregulation has to be considered, and can occur with stress, toxin, heavy metal and pesticide exposure, dysbiosis, hormonal imbalance, nutrient imbalance, infection, inflammation, and radiation. Chemotherapy is also a major cause of immune dysregulation; for example, vincristine is weakly myelosuppressive, and cyclophosphamide and glucocorticoids are strongly myelopsuppressive.
Many chemotherapeutic drugs currently in use in medicine were first identified in plants, including taxol, vinblastine and vincristine, and etoposide and teniposide. Herbs offer a rational potential in the treatment of cancer in animals; however, it is important to note that herbs may be used for purposes other than direct antitumor activity. On the other hand, just about any selection of herbs prescribed to treat a patient will more than likely have some anticancer activity because of the presence of widely occurring anticancer constituents like flavonoids.
Although little research has been conducted in cats and dogs specifically, a plethora of research pertains to rats, mice, hamsters, and guinea pigs. At least pocket pets are amply catered to if they are diagnosed with cancer! Herbs can be used to help manage the effects of chemotherapy; to assist in recuperation after chemotherapy, radiation, or surgery; to complement conventional cancer treatment; to provide an alternative to conventional treatment in some cases; to assist in cancer prevention; and to support various systems that are affected by cancer. One of the approaches used by veterinary herbalists is to treat cancer as a chronic disease, with emphasis on improving the health of the whole body, regardless of the presence of cancer. Anecdotal evidence from veterinary herbalists indicates that herbs offer improved quality of life and may support remission in some cases.
The rational use of herbal medicine for the treatment of patients with cancer depends on a growing understanding of the biological mechanisms by which cancer cells proliferate, maintain life, and die. These include differentiation (the maturation process of cells), angiogenesis (the growth of new blood vessels into tumors), apoptosis (programmed cell death), invasion (the spread of the tumor mass into adjacent tissue), metastasis (the spread of tumor cells to distant locations), mitosis (the proliferation of cells), and evasion of the immune system. As these mechanisms have become elucidated, their weak points have been identified and have become the targets of research that is both conventional and complementary. The selection of several herbs that have different mechanisms of action provides a broad spectrum of anticancer activity. A holistic strategy that incorporates all elements discussed here is proposed under “Review of Strategies for Cancer Prescriptions” at the end of this post.
|Targets Unique to Neoplastic Cells for Cancer Therapy|
|• Genetic instability|
|• Abnormal transcription factor activity|
|• Abnormal signal transduction|
|• Abnormal cell-to-cell communication|
|• Abnormal angiogenesis|
|• Invasion and metastasis|
|• Abnormal immune function|
Mechanisms of Interest
It is logical to select herbs is on the basis of cancer biology. An extremely comprehensive review of anticancer plants and natural compounds is provided in John Boik’s book, Natural Compounds in Cancer Therapy (2001). This book explains in great detail the mechanisms of action of many plants and their constituents. It is important to note that most herbs have many actions, and this list is merely indicative of the wide range of such mechanisms that have been documented. (Search Medline for more information; use the herb name and cancer or activity as search terms.)
Boik highlights the importance of synergism as a strategy by which lower doses can be used without reduced efficacy; he also discusses the use of herbs with different antineoplastic mechanisms for targeting events that take place in the progression of cancer. Choosing compounds that have direct-acting, indirect-acting, and immune-stimulating activities is likely to inhibit procancer events. Constituents like flavonoids can target multiple aspects of tumor biology.
Anticancer Mechanism of Selected Herbs and Constituents
|Apoptosis Inducers||Inhibitors of Local Invasion|
|• Greater celandine (Chelidonium majus) (Note: This is a very strong herb that is usually administered topically.)||These are herbs or constituents that inhibit hyaluronidase and its assistant enzymes or elastase, or that affect collagen or cell migration.|
|• Baical skullcap (Scutellaria baicalensis)|
|• Bupleurum (Bupleurum falcatum)||• Gotu kola (Centella asiatica)|
|• Boswellia (Boswellia serrata)||• Horse chestnut (Aesculus hippocastanum)|
|• Turmeric (Curcuma longa)||• Butcher’s broom (Ruscus aculeatus)|
|• Saint John’s Wort (Hypericum perforatum)||• Turmeric (Curcuma longa)|
|• Garlic (Allium sativum)||• Panax (Panax ginseng)|
|• Flavonoids (apigenin, luteolin, genistein, quercetin, reversatrol)||• Hawthorn (Crataegus spp)|
|• Bilberry (Vaccinium myrtillus)|
|Differentiation Inducers||• Dong quai (Angelica sinensis)|
|• Burdock (Articum lappa)||• Flavonoids (proanthocyanidins, anthocyanidins, apigenin, reversatrol, genistein, luteolin, quercetin)|
|• Boswellia (Boswellia serrata)|
|• Berberine||• Mushroom polys ace ha rides|
|• Flavonoids (reversatrol, apigenin, luteolin, genistein, quercetin)||• Emodin|
|• Boswellic acids|
|• Emodin||Inhibitors of Metastasis|
|Cytotoxic Agents||These are herbs or constituents that have anticoagulant activity.|
|• Mistletoe (Viscum album)|
|• Limonene||• Aloe succus (Aloe vera)|
|• Emodium||• Green tea (Camellia sinensis)|
|Inhibitors of Angiogenesis||• Cordyceps (Cordyceps sinensis)|
|• Reishi mushrooms (Canoderma lucidum)|
|These include herbs and constituents that inhibit increased vascular permeability, or that beneficially affect prostanoid and leukotriene systhesis, or that inhibit mast cell degranulation.||• Garlic (Allium sativum)|
|• Panax (Panax ginseng)|
|• Astragalus (Astragalus membranaceus)|
|• Dong quai (Angelica sinensis)|
|• Butcher’s broom (Ruscus aculeatus)||• Feverfew (Tanacetum parthenium)|
|• Gotu kola (Centella asiatica)||• Dan shen (Salvia miltiorrhiza)|
|• Horse chestnut (Aesculus hippocastanum)||• Turmeric (Curcuma longa)|
|• Garlic (Allium sativum)||• Flavonoids (including reversatrol, anthocyanidins, genistein, apigenin, luteolin, quercetin)|
|• Turmeric (Curcuma longa)|
|• Siberian ginseng (Eleutherococcus senticosis)||• Emodium|
|• Ginkgo (Cinkgo biloba)|
|• Picrorrhiza (Picrorrhiza kurroa)|
|• Flavonoids (including proanthocyanidins, anthocyani-dins, reversatrol, genistein, apigenin, luteolin, quercetin)|
This strategy recognizes that a patient can live with cancer as opposed to having to die of cancer. Many of our elderly animal patients, in particular, have never been in better health than when they are on herbal and nutritional treatment, even though they have cancer, because the prescriptions that they are given promote overall health. Herbs should be used to strengthen body resistance, and vitality is enhanced through the use of adaptogens. Most adaptogens also have anticancer activity.
Astragalus (Astragalus membranaceus): Astragalus induces cell differentiation and cell death in vitro and exerts anticarcinogenic effects through activation of cytotoxic activity and the production of cytokines in mice.
Ashwagandha (Wlthania Somnitera): The anti-tumor and radiosensitizing effects of Withania have been studied. Growth of carcinoma in mice was inhibited and survival increased with Withania treatment, especially when it was combined with radiation. When given before irradiation, it synergistically increased survival, even in mice with advanced tumors. Complete regression of sarcoma in mice caused by Withania root extract was observed.
Eleuthero (Eleutherococcus Senticosis): This herb was able to inhibit tumor growth and prolong survival time in tumor-bearing mice; these effects were significantly related to enhanced immune response. Siberian ginseng appeared to reduce the quantity of conventional antimetabolites that were needed to attain antiproliferative effects on tumor cells in vitro.
Asian Ginseng (Panax Ginseng): This herb induces cell differentiation, reduces the effects of chemical carcinogens, mitigates inflammatory carcinogenesis, induces apoptosis, inhibits proliferation, and has proved beneficial in the treatment of a number of cancers in humans.
In traditional herbal medicine, alteratives represent a key strategy for the treatment of cancer. Alteratives act through the lymphatic, blood, and eliminatory systems to facilitate and enhance the breakdown and removal of metabolic wastes. They are also used to improve the absorption and assimilation of nutrients. Alteratives are thus considered to be “blood purifiers” or “detoxifiers”, believed to circulate and improve blood flow, while removing waste from blood and lymph. The function of these herbs is to optimize the body’s eliminative functions performed via the liver, kidneys, lungs, and gastrointestinal system.
Ideally, these herbs are chosen according to their other actions and affinities for particular organs or systems, so as to maximize their benefit. For example, poke root and cleavers are specific for the lymphatic system. Many of these herbs contain alkaloids and flavonoids and have documented anticancer activity; many others have not been studied. Modifying prescriptions every 2 to 3 months reduces the risk of potential toxicity associated with some of these herbs.
Alteratives include the herbs listed here:
Burdock (Articum Lappa): Differentiation-inducing activities have been demonstrated against mouse myeloid leukemia cells. The most active derivative induced more than half of leukemia cells to become phagocytic cells.
Dandelion root (Taraxacum officinale): in vitro antitumor activity has been documented for an aqueous extract of dandelion. The mechanism of action was thought to be similar to that of tumor polysaccharides such as lentinan.
Sheep Sorrel (Rumex Acetosella): One study found that Rumex acetosella polysaccharide displayed antitumor activity in mice that were implanted with sarcoma (180 solid tumors).
Oregon Grape (Mahonia Aquifolium): Berberine has anticancer activity and exhibits the ability to induce apoptosis in leukemia cells. In addition, some protoberberines are highly effective as cytotoxic agents against several carcinoma lines; berberine consistently showed the highest cytotoxicity among the alkaloids tested.
• Barberry (Berberis vulgaris)
• Echinacea (Echinacea pupurea)
• Stillingia (Stillingia sylvatica)
• Yellow dock (Rumex crispus)
• Poke root (Phytolacca decandra)
• Cleavers (Gallium aparine)
• Red clover (Trifolium pratense)
Cancer patients suffering pain may be administered anti-inflammatory, antispasmodic, and analgesic herbs as necessary. A review of these herbs can be found in the section on neurology, pain, and behavior.
Platelet-Activating Factor Inhibitors
Platelet-activating factor (PAF) is an ether-linked phospholipid that has been postulated to be a stimulator of malignant tumor growth; it may be significant in the early stages of tumor development.
Ginkgo (Ginkgo Biloba): Ginkgolides have been reported to competitively inhibit the binding of PAF to its membrane receptor.
Coptis (Coptis Chinensis): This herb was investigated in mice bearing colon carcinoma cells that cause IL-6-related cachexia after cell injection. Coptis significantly attenuated weight loss in tumor-bearing mice compared with controls, without changing food intake or tumor growth. It was therefore shown to exert an anticachectic effect associated with tumor IL-6 production, and it was suggested that this effect might be due to berberine.