Hallmarks of cancer

English: Cancer cells photographed by camera a...

English: Cancer cells photographed by camera attached to microscope in time-lapse manner. (Photo credit: Wikipedia)

II was inspired to add another blog today after a friend/former colleague of mine came in to see me and mentioned he had been reading my blog (thanks Allan).  So, today I have decided to embark on describing the hallmarks of cancer as we now understand them (hopefully using simple words and concepts as some of this does get kinda’ murky).

In 2000, a well known cancer scientists named R. Weinberg and his colleague published a review of the major hallmarks of all cancer cells (and thus of cancer itself).  In that original publication, he described six hallmarks, that was an increase in the previously established two.  There are now about eight that are widely accepted.  So, let’s start with the original two.

We all have normal tissues and cells in our body and many of the cells turnover relatively frequently.  Cellular turnover refers tot he process of dying and dividing cells.  Thus, new cells are made from dividing older cells and other old cells die off.  As the new cells are made, some of them may acquire new mutations.  Some of the cells may also have old mutations or may even harbor mutations that were inherited.  If these mutations affect the survival of the cells than we call them oncogenes (#1 hallmark).  If these mutations prevent the killing (or what is known as apoptosis, or programmed cell death) then the cells don’t die when they are supposed to (the #2 hallmark of cancer).  We have known for many years that all cancer cells derive from cells that keep growing and that don’t die.

Later, we started to appreciate that there were some other characteristics that we could ascribe to all cancer cells in addition to these two.  Instead of needing to turn on and off growth signals like normal cells, cancer cells are self sufficient in growth signals.  That means that the signals that make the cells grow, don’t turn off.  As long as their is cellular energy, then the cells keeps going.  That is hallmark #3.  Another attribute that all cancer cells have is that they are actually insensitive to growth signals, this is in addition to the fact they they evade death signals.  So, the signals that they receive from death inducing agents are either ignored or fuel growth or expansion. That is the 4th hallmark.  Two additional changes occur that are universal to all cancers, but some early cancers may not progress o this state.  One of these is the promotion of sustained blood supply to the tumor and thus the cancer cell (supplying it with nutrients and oxygen, etc.).  This 5th hallmark is also known as angiogenisis.  Looking at cancers that have advanced it is clear that they have increased vascular supply than the surrounding tissues.  Finally, the 6th hallmark of cancer is that of tissue invasion.  Aggressive cancers and the cells that make them up typically run out of food supply and become more aggressive and seek out new areas of the body.  In order to do so they need to secret products that help them ‘digest’ their environment and all of the fibrotic material that accumulates.  This 6th hallmark of cancer is also referred to as metastasis.  The cancer is usually more aggressive and serious once it has moved onto and latches onto its new location.  It is also much harder to treat.

Two newly recognized and agreed upon processes occur in cancers as well (and thus the cells that make them up).  The 7th hallmark of cancer is the ability of the cancer cells to escape the immune response.  Normally, the immune response would look at mutated proteins (that are found in most cancer cells) and try to destroy them.  However, cancer cells evolve many unique ways to evade immune destruction and recognition.  Finally, the 8th hallmark of cancer cells is something called metabolic reprogramming.  This basically means that the metabolism of the cells itself no longer mirror what the normal cell has.  The genes, energy usage, and most metabolic processes have permanently changes into a more aggressive, energy hungry pro-growth state.

Thus, as you can see, cancer is not so simple.  The cells that make up the cancer have changed in so many ways.  This is partially why it is so hard to eliminate cancer once it has taken hold.  There are quite a number of pathways involved in all 8 of these processes.  Since the early 80’s we have really learned a lot about cancer; certainly we have learned how complicated they are.  We have developed drugs against every single one of these 8 hallmarks, but we have not been able to cure most cancers and permanently eliminate many tumors (especially of caught late).

Thank you for reading and i do hope that is made cancer a bit more easy to understand.
Do visit www.cancermadesimple.com for more information.

Dr. C