Silver Lining in News of a Silver Bullet

Silver Lining in News of a Silver Bullet

Science outreach is one of the reasons I spend a lot of time on G+. It’s one of the reasons I care about G+ as a platform. If you follow me, you might have seen me bellyache about getting notifications from people I don’t have circled and how that interferes with my science outreach (mostly curating #ScienceSunday ). Today I’m going to share an example of why it is important to me for people to be able to notify me about science.

❒ Science Outreach

Michael Davis read an article in TIME magazine (http://goo.gl/elCMSa) and wondered if the claim that chemotherapy would be a thing of the past was true. So he mentioned me in his post and I looked at the article and realized it was another case of sensationalizing some exciting research. The fact that Michael follows my posts enough to trust my opinion about cancer, really pleases me. It is very fulfilling to  be able share my knowledge with people who want to learn. It’s interactions like this that make me tolerate any negativity on G+, e.g. trolls. It’s people like Michael that make me want to post more science and get better engagement on my science posts.

❒ Sensational Headlines

The TIME article discusses a recent phase 1-b clinical trial for a new cancer drug. I explain more about it below. The claim that traditional chemotherapy will be a thing of the past is not only premature, it’s also misleading. There will still be cases where current treatment (surgery, radiation, and non-targeted chemotherapy) is an appropriate course of action. Say for example, someone receives a PET scan and it reveals tumors throughout the patient’s body. It doesn’t make sense to biopsy all of those tumors and it is possible that all of those tumors aren’t genetically identical. So some of the advanced targeted therapies would not be applicable. See Buddhini Samarasinghe’s post (The Signatures of Cancer http://goo.gl/LmyS0z) to get a sense of the variability in tumors. 21 distinct mutational signatures are discussed.

Many of us have posted about sensationalizing headlines before.

Science is already Sensational

http://goo.gl/LmiQDe via Buddhini Samarasinghe 

Bench to Bedside

http://goo.gl/xudsu via me

Viral Vectors Versus Viral Video

http://goo.gl/q4Bk7 via Rajini Rao 

PhD Comics: The Science News Cycle for fun

http://www.phdcomics.com/comics.php?f=1174

❒ Silver Bullet

Here’s how I replied to Michael’s post.

A quick glance at the article suggests they are really trying to say that broad spectrum (to borrow the terminology from antibiotics) are being phased out in favor of targeted therapies. This isn’t really new or news. One example they give is imatinib or Gleevec. Imatinib targets a specific type of enzyme, a tyrosine-kinase inhibitor. You can read the Wiki on it or I can write more later. The important thing is that imatinib builds on knowledge from previous tyrosine-kinase inhibitors like sorafenib, which has an antiangiogenic mechanism. It targets new blood vessels, which the tumor creates. As far as the HIV comment, check out Rajini Rao’s post (http://goo.gl/q4Bk7) if you haven’t already. There’s comments about other gene therapies in there too.

Backing up a little bit, a protein kinase, is an enzyme that’s involved with a process called phosphorylation, where a phosphate group is transferred from a high energy molecule to a specific substrate. A tyrosine-kinase is just a type of kinase where the phosphate group is attached to tyrosine (an amino acid). Phosphorylation is often described as a molecular on/off switch. When a protein is phosphorylated or dephosphorylated it can be switched from on to off or vice versa.

So the new drug in the article, ibrutinib, is a Bruton’s tyrosine kinase (BTK) inhibitor. BTK is essential for the proliferation of chronic lymphocytic leukemia cells. As mentioned in my comment above, it builds on prior knowledge of kinase inhibitors. In my opinion, it’s not a revolutionary breakthrough. It’s an important and fantastic step forward. It is not a silver bullet.

❒ PDX

An example of another targeted drug that’s been around for a while is tamoxifen. It targets estrogen receptor positive (ER+) breast cancer. For breast cancer, a biopsy is often taken when there is a suspicious lesion in a mammogram, ultrasound, or MRI. The biopsy might reveal that the lesion is in fact cancer and is ER+. In that case it is reasonable to try tamoxifen. My point here is that targeting is not new, even though the targeting is getting more specific.

A colleague is working on an exciting project called PDX, patient derived xenograft. What that means is that a piece of the patient’s tumor is taken to the lab on ice and implanted in immunocompromised mice. That’s called a xenograft, i.e. grafting from different species. Typically cancer research is carried out on tumor cell lines that are well characterized and have been around for a long time. The problem is that some of those cell lines don’t fully resemble the tumor in the patient scenario. The PDX project has the potential to better model the patient scenario as we know exactly where the tissue came from. More importantly, it allows us to better target that specific tumor. That’s exciting work without making it sensational and it won’t be a silver bullet either as some tumors might not grow in a mouse.

Image source:

V.A. “Vinnie” Musetto “Headless Body In Topless Bar”

http://goo.gl/1suPQK

I picked this image because Mr. Musetto was well known for writing sensational headlines.