Cancer continues to be one of the most troubling diseases in Canada with more than 206,000 new cases each year and 80,000 deaths. Progress has been made over the last two decades as treatment options have grown and survival rates have improved. Yet the battle continues.
Since the 1990s, one of the approaches to fighting tumours has been the use of viruses capable of killing cancer cells on the inside. This approach, known as oncolytic therapy, has made waves in the cancer world, and in 2015, the first viral treatment for melanoma was given official approval for use in the United States.
While this step has been hailed as a milestone in fighting cancer, many concerns continue to linger in terms of the use of viruses to fight cancer. One of the most important happens to be what is known as targeting. As the name implies, this factor ensures the virus attacks only the tumour while ignoring normal cells. This continues to be a major factor in any testing before thinking about clinical trials.
Along the oncolytic virus journey, some researchers decided that a different plan might be better. Instead of using cancer-killing animal viruses, they used bacterial viruses, known as bacteriophages, as carriers to deliver drugs directly to the cancer cell. This concept was faster and could be used for a wide array of cancers. Unfortunately, the process has yet to demonstrate its true value as tests have shown minimal effect on tumours.
Despite the disappointment, there was a silver lining: the technique revealed drugs could be used to target cancer cells using some type of biological delivery system other than a whole animal virus. All researchers figured they needed to do was find a suitable candidate that could work better than a bacteriophage.
As it turns out, one already had been discovered. It was just in a very different research environment. The answer lied in the realm of research into the human immunodeficiency virus, better known as HIV.
Back in 1997, a group of French HIV researchers were looking at a component of the virus known as the transactivator protein, or Tat. They discovered a certain section of the molecule had the ability to penetrate cells all by itself, without damaging them.
This region eventually became known as the cell-penetrating peptide, or CPP, and a few years later, the team proved it could be used as a delivery system for drugs. Not long after, other CPPs were identified and they too showed promise as needle-like delivery systems. Although it would take some time, the idea of using CPPs to combat disease began to take hold.
Now, the CPP concept may offer the chance to fight cancer thanks to a recent study from a Malaysian team of researchers.They have shown these molecular needles can get into skin cancer cells and deposit whatever might have been attached to them. The results suggest one day we may have a new and efficient option to tackle tumours.
To get to their goal, the group first needed to find a CPP that would invade cancer cells but not normal skin cells. They screened a number of different peptide sequences through a process known as biopanning,which is designed much in the same way as a tournament. A series of rounds are performed in which the peptides are given the chance to get into a cell. Those that don't succeed are eliminated from the contest. Those that find a way into the cells must continue to perform with every round or face being left behind. The technique is so effective, a champion is found usually by the third round.
In this case, the researchers found their candidate on that third round. It was a peptide that could penetrate the cancer cells and ignore normal ones. It wasn't given a fancy name though. It was just known by its letter coded amino acid sequence, NRPDSAQFWLHH.
With the peptide in hand, it was time to test its ability to act as a delivery system. The team attached the peptide to nanoparticles and observed whether they were shuttled into the cell via the CPP needle. Not surprisingly, the test was a success as the nanoparticles easily went inside the cells. They had shown CPPs could be used to help invade cancer cells and with the right attachments, fight them.
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Apart from the results of this study, which focused on skin cancer, the authors suggest their peptide could have an effect on a variety of tumour types such as lung, esophageal, gastric, prostate, colorectal, bladder, pancreatic, ovarian and renal cancers. Whether this holds true is a matter of testing. If there isn't a perfect match, thanks to biopanning, an alternative could be identified relatively quickly. Nevertheless, the dawn of the CPP needle in the fight against cancer has begun.
Of course, to get to a real treatment, much more work needs to be done. Studies in the lab and in trials will be needed to confirm CPPs as effective weapons. However, in light of the continuing worry of cancer in Canada and worldwide, the advent of this technology may be a sign that victory over cancer is getting closer.