Targeted Treatment

Over the past few decades, the amount of research into cancer and the improvements made in treatment have been extraordinary. In the not so distant past, chemo and radiation therapies for cancer were so extreme that they often took patients to the brink of death. Severe weight loss, hair loss, anemia, and in a state of medically induced immuno-suppression, cancer patients and their families had to go through months of emotional and physical exhaustion. And, there was no guarantee of survival. On top of that, there was a high recurrence rate, and often the patient developed a resistance to the drugs used.(1)

In short, cancer treatments were inefficient at best – and very expensive.

Which makes this study published in November of 2020 by the American Association for the Advancement of Science so exciting. A team of researchers has developed a cancer therapy (CRISPR-Cas9) so simple, so specific, that with one treatment a tumor is eradicated. This research has been done with mice so far, but there is reason to hope that the same efficacy will be found for humans.

CRISPR-Cas9 and Genome Editing

The science can be a bit dense when looking at this new cancer treatment, but it’s worth getting a quick review of how this new therapy works. Genome editing (or gene editing) is the incredible technology that allows scientists to change an organism’s DNA – add, remove, or alter genetic material at a one specific location. CRISPR-Cas9 is a particularly interesting gene editing treatment because it is faster, cheaper, and more accurate than any of the other genome editing methods currently available.

What makes CRISPR-Cas9 even more interesting is that it was adapted from a naturally occurring genome editing system in bacteria.

• Scientists noticed that bacteria were capturing pieces of DNA from invading viruses and using them to create DNA segments known as CRISPR arrays.
• CRISPR arrays allow the bacteria to “remember” the viruses.
• If the viruses attacked again, the bacteria produce RNA segments from the CRISPR arrays to target the viruses’ DNA.
• The bacteria then use Cas9 or a similar enzyme to cut the DNA apart, which disables the virus.(2)

The advent of CRISPR technology has revolutionized the biological sciences and provided cancer biologists with a powerful gene-editing method that can alter the genetic make-up of cells in unprecedented ways. Indeed, promising results have been achieved in diverse disciplines, from basic research to the development of potential therapies against cancer, congenital defects, and other chronic diseases.(3)

Ongoing Challenges

CRISPR technology is still relatively new, so there are still a number of issues that need further exploration, and resolution, especially related to safety (i.e. improve targeting efficiency and minimize off target effects). There is also some concern about how CRISPR agents affect the immune system – the Cas9 protein is, after all, bacterial in origin.

Delivery methods are a different in review. The two most common means of delivery are by viral delivery (using a virus to deliver the genes) or through microinjection. Both are effective, though with viral delivery there is the risk of eliciting a strong immune response in animals, which, in turn, affects the viral delivery of the genes.(3)

There are also ethical questions that should be considered when looking at the future application of CRISPR technology. Right now, much of the research centers on somatic cells (cells which are not egg or sperm cells), meaning that changes in genome affect certain tissues – and, these changes are not handed down from one generation to the next. But cell and embryo genome editing is a possibility which leads the the ethics of genetic alterations. Should CRISPR technology be allowed to enhance normal human traits (height, intelligence)? Because of these ethical concerns many countries have banned genome editing.(2)