Indirect ways to inhibit cancer spread
Subject: One way to slow cancer spread is to use supplements which affect connective tissue and decrease the ability of cancer cells to invade healthy tissue. A number of natural compounds typically used to strengthen connective tissue hinder cancer cells by inhibiting the enzymes cancer cells secrete to dissolve the extracellular matrix of connective tissue which normally blocks their migration.
There are a number of supplements which act indirectly to slow cancer cells from invading surrounding tissue. It is interesting that most are more commonly used for the treatment of varicose veins and hemorrhoids. This is such an uncommon use for these products that it is necessary to elaborate the rationale behind these recommendations.
Invasion, the spread of cancer cells into adjacent tissue, is one of the distinguishing features of malignancy. Invasion and metastasis are closely related: cancer cells must generally invade connective tissue surrounding blood vessels for metastasis to be successful.
Cells in the body don't actually lean against each other, cheek to jowl. They are interspaced between connective tissue. Connective tissue varies from very firm materials such as bone, tendon and ligament, to a spongelike gel that surrounds individual cells. This soft connective material is referred to as the extracellular matrix (ECM). This is what holds us together. It is composed of a complex gelatinous material woven together of glycoaminoglycans (GAGs). They are spongelike, hydrophilic (water loving molecules) made from repeated sugar chains. Nutrients, vitamins, and minerals pass through this gel-net to reach the cell surfaces. Waste products from the cell pass back through on their way to the blood system.
This extracellular matrix is a barrier to tumor invasion. It governs the behavior of the cells it surrounds. Most normal cells when removed from their surrounding extracellular matrix will undergo apoptosis and self destruct. Cancer cells often don't care about ECM and can live without it. Normal cells secrete the material to surround themselves with ECM, cancer cells don't. Instead cancer cells produce a matrix that helps them migrate and proliferate.
Cancer cells produce enzymes so they can break free of the ECM. Two types of enzymes are necessary: protease (protein digesting enzymes) and glycosidase (glycoside digesting enzymes). These enzymes allow cancer cells to digest and dissolve the extracellular matrix (ECM) allowing the cells to spread.
There are many different types of these enzymes but the ones most important for this discussion are the collagenases, a type of protease that digests collagen and hyaluronidase, a type of glycosidase that digests hyaluronic acid.
Hyaluronic acid is one of the most common GAGs which make up the ground substance of ECM. Hyaluronidase, the enzyme which digests hyaluronic acid, can cut channels through the ECM helping cancer cells invade surrounding tissues. Though these enzymes play important roles in health, in cancer the goal is to reduce their activity in order to reduce the potential for cancer cells to spread. A number of natural substances will slow the action of hyaluronidase, the enzyme which degrades hyaluronic acid. They are:
Collagenase enzymes break down collagen, the fibrous material found in connective tissue. Reducing collagenase activity makes it more difficult for cancer cells to invade surrounding tissue. Various natural substances affect this process: Here is a list of natural compounds which either inhibit collagenase activity, increase collagen synthesis or stabilize collagen:
Many of these compounds listed are commonly used in treating varicose veins or hemorrhoids. The pathology of varicose veins is very similar to cancer invasion. In both cases intermittent blood stasis causes tissue hypoxia (suffocation) and reperfusion which leads to free radical generation. The free radicals degrade the collagen of the ECM and basement membrane. In addition collagenases are produced which further degrade the collagen. In both diseases, normal matrix isn't made.
There is one additional aspect to tumor cell invasion. Cancer cells “walk” through the extracellular matrix using surface adhesion proteins to grip specific chemicals in the extracellular matrix. Special proteins act as ‘legs' on the surface of the cell. They attach to hyaluronic acid and collagen, pull the cell through the matrix to the proteins, absorb the protein, digest it, and move on. The more of these special ‘leg' proteins the cancer cells make the more aggressive the malignancy. There are a number of natural compounds which inhibit cancer cell migration by inhibiting the production of these protein ‘legs.'
What all this boils down to is that in situations where there is active malignancy, treating it as if it were just a bad case of hemorrhoids may prevent cancer cells from invading adjacent tissue and decrease the chance of metastasis. Not all the substances mentioned in this discussion are commonly available. Here are the suggested doses for the more common of them. 
 Boik, John. Natural Compounds in Cancer Therapy.Oregon Medical Press. 2001 appendix J dose calculations.