Hi Selma

In my hands those kind of sample often produce bad quality RNA , which is often degraded. The results depend on the gene that you are trying to study. In general genes with higher levels of mRNA will produce reasonable results. On the other hand, transcripts with low RNA abundance are completely useless for comparing samples. You must be careful about that...

If you want to compare samples I will advice you to use miRNAs, which are more stable under those conditions.

Hope it helps. Cheers

Paco

thank you very much, both answers are very useful for me. Dr. Enguita, actually miRNA seems more acceptable for me too, but I never worked with miRNAs. I isolated RNA from fresh breast tumor samples. I have some more homogenised samples from these tumors waiting in -70 degree. I had homogenised them in the RNA later solution. Do you think I can use them for miRNA isolation?

Selma

If the RNA is correctly isolated (using kits or Trizol-like reagents) everything will be fine to profile miRNAs. miRNAs are more stable than bigger messenger RNAs. So, in principle you must have the miRNAs around in your extracted samples. However the yield of extraction depends on the protocol that you used.

What is the protocol (or kit) that you used to extract total RNA from samples?

Best. Paco

Actually i collected tumor samples in RNAlater, after about two months i homogenised them using a bead protocol and isolated RNA with qiagen RNAeasy kit. But i do not have much isolated rna , i rather have those that i homogenised in rnalater solution (homogenised samples were generally excess than i need, so i only used some of them)so as i understood, i can use these samples for miRNA experiments after isolating total Rna, right?

Thank you so much for your help