[Immunology] CT26.CL25 tumor progression in BALB/c mice-NOT!

[geoffreycole at verizon.net]

I'm interested in hearing from anyone who has transplanted the
CT26.CL25 b-gal+ tumor line into BALB/c mice.  Restifo and colleagues
generated a series of publications in the mid to late 1990s in which
they showed that the b-gal (+) CT26.CL25 colon carcinoma grew as
progressively in susceptible BALB/c hosts as did the parental CT26.WT
parental tumor line.  I'm well familiar with the mechanistic spin:
b-gal neo antigen expressed on tumor line is not immunogneic due to
absence of appropriate co-stim molecules.  Susceptible mice primed
prophylactically/therapeutically to b-gal were  immune to b-gal (+)
transductant but, not b-gal (-) tumor.

I've performed dose-rainging studies in which normal 10 wk old female
BALB/c mice were challenged SQ in parallel with both the parental tumor
and the b-gal transductant at an inputs of 1e5, 1e4, and 5e3 viable
cells. Parental tumor grew progressively with 80% tumor in all groups.
In CT26.CL25 challenged mice, tumor incidence was 40% at 1e5 input, 20%
at 1e4 input, and no tumor incidence at lowest challenge dose.  Assayed
both tumor (+) and tumor (- ) mice 18 days after CT26.CL25 challenge by
stimulation of spleen cells with b-gal 876-884 peptide in IFN-g ELISPOT
and detected 100-150 SFC/1e6 splenocytes.  Paired control using
splenocytes from CT26.WT tumor bearing hosts showed no evidence of
b-gal peptide-reactive cells.  My tumor llines were obtained from ATCC
and I've verified that the parental and the transduced tumor cell lines
are  b-gal (-) and b-gal (+), respectively.

I'm neither surprised nor am I casting doubt on the originally reported
results with this tumor line.  Rather, I'm curious as to whether others
have made similar observations.

Thanks.