Frequently Asked Questions:
1. What is the best way to store normal solid tissue and blood for
future unknown DNA, RNA, Protein and other biomarker-related studies?
Frozen tissue is still the absolutely best form. The HTRN is completing studies
comparing the type of packaging for frozen tissue that provides the best long term
storage. Studying the effects of vacuum packing the tissues in a new material that
blocks out light and oxygen to prevent any oxidation and water loss (sublimation) over
time looks promising. For long term banking this may pose to be the best method, but
proof is still being collected. This concept follows food industry research and technology.
Most researchers place their sample in a cryovial and freeze at -80C (electric freezer) or
-190C (LN2), either are suitable over several months, but if storage will be for longer periods
of time, it's expected that there's a greater loss in RNA's stored at -80C and degradation in
some proteins. DNA is the most stable.
The HTRN has the ability to vacuum pack samples. DNA, RNA, and proteins would all be protected
best because all are affected (diminished or structurally difficult to label in testing) when
oxidation and water loss occur.
Blood is stored in standard cryovials and frozen at -80C. The HTRN has not seen any significant
publications on differences between -80C and -190C for fluids, although we're confident there
could be over years of storage. The NCI Office of Biorepository and Biospecimen Research is
planning to provide a report on these issues sometime this year.
2. How much should be stored and in what aliquot sizes for multiple studies?
The HTRN usually stores tissues in aliquot sizes from 0.250 gms to 2-3 gms. For blood
about 1.0 ml per vial, but it can be larger depending on the number of times the sample
will be used, which if it will be three or more samples pulled at different intervals then
more aliquots are needed to prevent thawing and refreezing.
3. What would the HTRN charge to prepare and store these samples?
The HTRN provides this on a project by project basis because of the many ways in
which the samples can or need to be stored.
4. What is the gold standard for determining DNA, RNA and protein integrity
in stored samples?
The gel electrophoretic measurement and PCR amplification of housekeeping genes for GAPDH
and B-Actin still suffice for DNA. For RNA, using an Agilent Bioanalyzer which measures the
18S and 28S peaks for ribosomal RNA clearly shows when a sample is degraded.
