In the past, it was assumed that tumors spread by invasion alone.

However, new evidence suggests that cancer stem cells can alter surrounding cells in ways that causes those surrounding cells to support the cancer’s growth and even transform their stem cells into cancer stem cells.

Some have called this the “soil and seeds” hypothesis.

What this means is that the cancer stem cells (the seeds) are implanted in rich soil (tissues that are inflamed).

Now we realize that these cancer stem cells can fertilize their own garden — unlike plants in a regular garden. They do this by making surrounding normal cells supply the fertilizer.

When a tumor enters the bloodstream or the lymphatic system, it is not the cancer cells that have been made by the stem cells that cause the malignancy to spread.

Rather, it is the cancer stem cells that actually cause the tumors to spread.

This fact is important to understand because it explains why once a cancer spreads it is resistant to all traditional cancer treatments, such as chemotherapy and radiation treatments.

This is because cancer stem cells are resistant to these treatments. In fact, chemotherapy increases this resistance.

When even thousands of noncancer stem celltype tumor cells are transplanted into experimental animals, they will not develop into cancers.

Yet implanting just a few cancer stem cells can produce highly aggressive cancers that spread widely throughout the animal’s body.

It is also known that once the cancer stem cells enter the bloodstream, they become much more aggressive and malignant.