I promised my mother that I would give you guys clearer run-down of my project. I’ve decided to plop down in the park, watch the swan boats patrol the pond, and run through it with you while a guy picks some Eagles songs on his acoustic guitar. My part of the project has developed into a toxicology study of two cell types. The first type of cells was taken from a biopsy of a patient’s primary colorectal tumor (in the lower bowels). The cells are flat and oval shaped, just like the cells that line your intestines, skin, and other organs. Another biopsy was taken of a metastatic tumor (a tumor that spread to a location somewhere else in the patient’s body; I don’t know where though). These metastatic cells are very different from the cells of the original tumor. They are more spherical than the parent cancer cells, they grow very fast, and there is some evidence that they are better at growing in low-oxygen environments. We suspect that these metastatic cells are hardier than the original tumor cells, which probably allowed them to survive their trip to their new location and grow under more stressful conditions.
One day someone discovered that an arm of chromosome 8 was chopped off in our line of metastatic cells, but not in the colonic tumor cells. That opened up a whole box of questions for Dr. Dedon and his fellow researchers. So many in fact, that several publications and multiple thesis projects later, many questions remain unanswered. Is there something important lying in the area of chromosome 8? Is there a regulatory gene in that area that suppresses the growth of the cancer cells? Did losing a gene on this arm of chromosome 8 allow the metastatic cells to grow more quickly than the primary cancer cells, which have the intact chromosome 8?
There are no genes in that area of chromosome 8 that we know would have been important in suppressing the haywire growth of cancer cells, so people began searching for new regulatory genes. Before I tell you what they found, I have to tell mom what I mean by “new genes.” Bear with me. Well you know mom is going to say, “New genes?! I thought we finished sequencing the entire human genome in 2003! Tell the NIH I want my tax dollars back!” Well, when the human genome was sequenced, we identified about 25,000 regions that looked like genes. We don’t know what all of those potential genes do, though. Decoding the genetic sequence has allowed us to characterize genes which code for many of our structural proteins and the enzymes that allow our cells to live (and some that allow them to die, like the apoptotic genes which allow cells to undergo programmed cell death). A lot of genes are not understood yet, and offer little clues to their purpose or function. Still, there are other uncharacterized genes which have known homologs, meaning they look similar to stuff that we understand in other organisms. In other words, we have a gene in humans, we don’t know exactly how it works, but we know how it’s genetic cousin works in yeast, or zebra fish, or something.
So what DO we know about the missing arm of chromosome 8? Some familiar genes were found there, probably not suspects for regulation of cell growth. Scattered among the known genes, there are a few uncharacterized ones. By adding these genes back into the metastatic cells, one at a time, somebody found which of these uncharacterized genes was able to slow down the growth of the metastatic cells. Adding this gene back into the metastatic cells slowed their growth back down to about that of the cells in the primary tumor. The gene had a name, and the name had an 8-digit alpha-numeric code. Email me if you’re dying to know. Dr. Dedon gave it a better name, hTRM-9. You’ll have to take my word, but it is a better name. We do know that hTRM-9 looks sort of similar to a gene that has been studied in yeast. The yeast cousin codes for an enzyme that increases the speed and accuracy of production of certain proteins in the yeast. So how might the loss of the similar human gene, hTRM-9, confer some sort of hardiness to the metastatic cancer cells? Let’s start by asking some more specific questions. Does hTRM-9 make the cells more resistant to hydrogen peroxide, a molecule that damages our DNA under conditions of oxidative stress? What about nitric oxide, a DNA-damaging chemical made by our immune system when inflammation occurs? Can cancer cells without hTRM-9 grow better in the low-oxygen environment of a tumor?
This is where my toxicology work begins. To answer our questions, I have to conduct experiments to compare the metastatic cells with and without hTRM-9. To make this possible, somebody re-inserted the hTRM-9 gene back into the metastatic cells, which, as you remember, had previously thrown the hTRM-9 gene out with the bathwater. These are now the +hTRM-9 cells. As a comparison to the +hTRM-9 cells, the scientist also inserted an unrelated gene called Lac Z into some other metastatic cells. Those +Lac Z cells should behave just like our normal metastatic cancer cells. So now we can test the effect of the hTRM-9 gene inside the metastatic cancer cells by comparing the +hTRM-9 cells to the +Lac Z cells. That’s my job. I treat both types of metastatic cells, +hTRM-9 and +Lac Z, with hydrogen peroxide, nitric oxide gas, or low-oxygen air (shown below) to see if the presence of hTRM-9 has an effect on their survival. If the +hTRM-9 cells die more easily than the regular +Lac Z cells, then we know why the metastatic cancer cells got so tough after the hTRM-9 gene was lost along with the missing arm of chromosome 8. If the +hTRM-9 cells don’t die more easily, then we keep looking for other ways to treat them. Hopefully we will find a treatment that illustrates the way that hTRM-9 makes the cancer more fragile! We have to repeat the experiments multiple times in order to have substantial confidence in any conclusions that we make. It will take some time in order to get a feeling of whether the hTRM-9 gene has a role in making the cancer cells more vulnerable to treatment.
With any luck, we will see something interesting! Thanks for reading, guys.
(Below – The +hTRM-9 and +Lac Z metastatic cancer cells, while their air chamber is refilled with air that is only 1% oxygen.)