Breast Cancer Vaccines 101: Two Different Types – Therapeutic and Prophylactic

By Dr. Kathleen T. Ruddy

There are two types of breast cancer vaccines:  therapeutic and prophylactic.

A.   Therapeutic breast cancer vaccines are made by first identifying a specific protein expressed by the cancer that is unique, i.e., only made by cancer cells and not by normal cells.  Once a scientist has found such a protein – and they are hard to find! – a vaccine is created that targets that unique protein.  The next step is to test the vaccine to see if it effectively eradicates tumor cells.

It’s also important that the vaccine not trigger an “inflammatory response” in the body that would render the vaccine useless due to side effects resulting from inflammation.  This is one of the many challenges that vaccine developers face.

Unfortunately, most attempts to make a useful, effective, non-inflammatory therapeutic breast cancer vaccine have failed.  There is one important exception, however, and that is the therapeutic breast cancer vaccine developed by Dr. Brian Czerneicki of the University of Pennsylvania School of Medicine.  Czerneicki has developed and tested a highly effective vaccine against a specific form of human breast cancer, Her+ DCIS (ductal carcinoma in-situ).

But, sadly – and not for lack of effort or enthusiasm – most therapeutic breast cancer vaccines have failed because malignant cells are so adaptable that by the time you create a vaccine to one unique protein, the tumor has already begun to express another that allows it to escape the vaccine and progress.

B.  Prophylactic breast cancer vaccines are made to prevent breast cancer entirely – the way, say, the Sabin oral vaccine prevents polio.  To date, only one prophylactic breast cancer vaccine has proven successful, and that’s the one developed by Professor Vincent Tuohy of the Cleveland Clinic in 2010.  As I mentioned in my last blog, Tuohy’s vaccine is 100% effective in preventing breast cancer in three different animal models.  His results were fully analyzed, vetted, and confirmed by the editorial review board of Nature Medicine, which published his paper in May 2010.

After proving first that his vaccine was 100% effective in preventing breast cancer, Tuohy then wondered if it might also have some therapeutic potential.  So he vaccinated mice whose tumors had already formed.  The results, as expected, were not encouraging:  only a modest decrease in the growth of the tumors was observed.  It is therefore unlikely that Tuohy’s prophylactic breast cancer vaccine will be useful in women as a therapeutic vaccine.  However, there is every reason to use the excellent results achieved in the animals studies and take the next step  – test Tuohy’s vaccine to see if it’s safe and effective as a prophylactic breast cancer vaccine for women.

By the way, Tuohy’s vaccine showed absolutely no inflammatory side effects.  This is important because the vaccine targets a protein, alpha-lactalbumin which is only made by women who are breastfeeding.  After breastfeeding ceases, alpha-lactalbumin is ‘retired’ – it simply vanishes.

One question that has arisen has to do with the possibility that Tuohy’s vaccine might trigger a massive inflammatory reaction in women who had once breast fed and, thus, had once made alpha-lactalbumin.  This is an important consideration, and one that must be settled by clinical trials.  However, Tuohy did not observe any inflammatory reaction to his vaccine when he used it in animals that had previously breastfed offspring, and consequently had once expressed and retired alpha-lactalbumin.

So, when scientists discuss breast cancer vaccines, it’s important that they clearly distinguish between therapeutic and prophylactic breast cancer vaccines – don’t mix your apples and oranges! – for therapeutic and prophylactic vaccines are designed with different goals in mind, and are sufficiently different, both in target and context (normal versus malignant cells), that it’s easy to get confused, muddled, and mistaken.   And once that happens, it’s quite hard to make any progress at all, even in conversation!

In summary, therapeutic vaccines, with the exception of Dr. Czerneicki’s against Her2+ DCIS, have all been disappointing.  On the other hand, there is only oneprophylactic breast cancer vaccine now in the queue, and it has proven astonishingly effective in preventing breast cancer in animal studies.

It must now be tested to see if it works in women.