drug sensitivity

Non-professional visitors (i.e., lay people, high school and undergraduate students) or professionals from other fields should use this forum for general questions regarding molecular biology. No guarantee that they'll be answered but you can always try!

Moderators: mchlbrmn, r.rosati

drug sensitivity

Postby pichia123 » Feb 18 2013 9:39 am

in my experiment, i want to study whether my target gene was associated with drug resistant in cancer cells. then I reduce the expression of my target gene by RNAi, and I found cell sensitivity to drug was increased. howecer when I increased the expression of my target gene by gene overexpression, cell sensitivity to drug was not influenced. does this possible? or does this mean my target gene is not associated with drug resistant?

Need help, thank you advance.
pichia123
technician-in-training
technician-in-training
 
Posts: 10
Joined: Aug 04 2012 10:25 am

Re: drug sensitivity

Postby relaxin » Feb 18 2013 12:52 pm

It is possible. If the gene encodes an eyzme that will destroy the drug, knocking down this gene expression by siRNA will increase the cell's drug sensitivity by decreasing its drug resistance. If the endogenous enzyme is already expressed in high level or is very efficient in destroying the drug, then over-expression of the gene will not further increase the cell's drug resistance. You will not observe any change in drug sensitivity.
Not affiliated with any company. Mention of a specifc product does not imply my endorsement of the product. No conflict of interest or guarantee to work on the advice given. Do as I say, not as I do. Not liable to the loss of your valuable samples.
relaxin
PI of Posters
PI of Posters
 
Posts: 6724
Joined: Jan 11 2006 12:40 pm
Location: Mauna Kea

Re: drug sensitivity

Postby pichia123 » Feb 18 2013 8:52 pm

Thank you for useful advice. Do you ever meet some example genes for this phenomenon?
As you said, it maybe right in my case. My target gene was higher expressed in tumor tissues compared to normal tissues. I used cancer cells to investigate drug sensitivity and the expression of my gene was relative high in cancer cells, so there was no difference in overexpression experiment. Is it optimal to use normal cells to do overexpression experiment?
Thank you very much.
pichia123
technician-in-training
technician-in-training
 
Posts: 10
Joined: Aug 04 2012 10:25 am

Re: drug sensitivity

Postby relaxin » Feb 19 2013 9:23 am

I cannot think of a specific example right off my head.
It is possible to use normal cells to do the over-expression experiments. The only problem is that the transfection is not very efficient, only a small portion of the cells will be over-expressing the gene of interest. You may try viral vector, if your lab is equipped for that kind of experiment. Alternatively, you can screen various cancer cell lines and find one that has low expression of the gene.
Not affiliated with any company. Mention of a specifc product does not imply my endorsement of the product. No conflict of interest or guarantee to work on the advice given. Do as I say, not as I do. Not liable to the loss of your valuable samples.
relaxin
PI of Posters
PI of Posters
 
Posts: 6724
Joined: Jan 11 2006 12:40 pm
Location: Mauna Kea

Re: drug sensitivity

Postby pichia123 » Feb 20 2013 8:34 am

Thank you, screening various cancer cell lines is a good idea. I also want to test the effect of my gene on cell drug sensitivity in vivo. I plan to use transplant nude mouse model. I plan to firstly establish a cell line (cancer cell) with lower expression of my target gene by infecting with RNAi lentivirus. Then I injected RNA lentivirus infected cells or control cells to nude mice and treated with drug. And finally evaluate my gene on cell drug sensitivity in vivo by comparing the tumor size of different group.
Another plan is to directly inject cancer cells to nude mice. After tumor grew, I first treat mice with the inhibitor which could decrease the expression of my target gene and then treat with drug. And finally compare the tumor size between two group (with or without inhibitor treatment).
According to your opinion, which plan is more correct? Looking forward to hearing from you.
pichia123
technician-in-training
technician-in-training
 
Posts: 10
Joined: Aug 04 2012 10:25 am

Re: drug sensitivity

Postby relaxin » Feb 20 2013 9:38 am

I think the RNAi lentivirus infected cells will be better, as the knock-down of the gene is specific to the tumor.
The inhibitor treatment may not target solely the growing tumor, and depending on the dose it may have serious side effect to the mouse.
Not affiliated with any company. Mention of a specifc product does not imply my endorsement of the product. No conflict of interest or guarantee to work on the advice given. Do as I say, not as I do. Not liable to the loss of your valuable samples.
relaxin
PI of Posters
PI of Posters
 
Posts: 6724
Joined: Jan 11 2006 12:40 pm
Location: Mauna Kea


Return to Student Questions

Who is online

Users browsing this forum: Google [Bot] and 3 guests