Table Of ContentOncoImmunology1:4,544–546;July2012;G2012LandesBioscience
CTLA-4 blockade synergizes with cryoablation
to mediate tumor rejection
Rebecca Waitz,1,* Marcella Fassò2,† and James P. Allison1
1DepartmentofImmunology;MemorialSloan-KetteringCancerCenter;HowardHughesMedicalInstitute;NewYork,NYUSA;2UniversityofCaliforniaSanFrancisco;
SanFrancisco,CAUSA
†Currentaffiliation:AduroBioTech,Inc.;Berkeley,CAUSA
Keywords: cryoablation, CTLA-4, Ipilumimab, SPAS-1, prostate cancer
Wereportthatcryoablationofprimarytumorssynergizeswithanti-CTLA-4treatmenttomediaterejectionofsecondary
tumorsintheTRAMPmousemodelofprostatecancer.Tcells,inparticularCD8+TcellsspecificfortheTRAMPantigen
SPAS-1,were enrichedinboth secondary tumors andspleens ofcombination-treated mice.
© 2012 Landes Bioscience.
The recently FDA approved immuno- inconjunctionwithIpilimumabmayboost unique system to study the induction of
therapy, Ipilimumab (commercial name theireffectivenessandincreasesurvivaltime systemic immunity and rejection of a
Yervoy) is a fully human monoclonal in a larger fraction of patients. While this secondary tumor challenge in mice treated
antibody that blocks the function of hypothesis is currently being tested in with anti-CTLA-4 and cryoablation com-
CTLA-4, an inhibitory receptor expressed clinical trials combining the use of a GM- binationtherapy.Ourpreviousworkinthe
by T cells. CTLA-4 is expressed and CSF-expressingtumorcellvaccine(GVAX) TRAMP model led to the discovery of
Do not distribute.
trafficked to the T-cell surface upon withIpilimumab,8wewantedtoinvestigate the CD8+ T-cell tumor antigen SPAS-1,
activation, and blockade of this check- whether this was also true when anti- which contains a mutation in its antigenic
point pathway, through administration of CTLA-4 was combined with tumor abla- epitope.10 SPAS-1 was identified as the
monoclonal antibodies, induces antitumor tion techniques. Local tumor ablation, target of a T cell line derived from the
immunity by promoting T-cell survival such as cryoablation, has occasionally spleen and lymph nodes of mice that
and proliferation.1 In clinical trials, been shown to lead regression of tumor receivedatumor-rejectingimmunotherapy:
Ipilimumabimprovedoverallsurvivaltime metastases,aphenomenonthatcouldlikely anti-CTLA-4 and GM-CSF-expressing
ofmetastaticmelanomapatientscompared be attributed to a systemic anti-tumor TRAMP cell vaccine. By this method,
with control groups.2,3 Studies in mouse immuneresponseresultingfromincreased, SPAS-1 was defined due to its highly
models, using a monoclonal antibody that albeit in most cases still insufficient, immunogenic character and was found to
blocks the function of mouse CTLA-4, antigen cross-presentation by professional betheimmunodominantTRAMPantigen.
showed that treatment with CTLA-4 APC. Starting from the assumption that This finding has enabled us to track
blockade as a single agent results in cryoablationwouldincreasecross-presenta- the specific CD8+ T-cell response in the
the rejection of immunogenic tumors.4 tion, we hypothesized that administration TRAMP model through the use of MHC
However, rejection of less immunogenic of anti-CTLA-4 during the destruction of Class I tetramers and ELISPOT assays.
tumorscanbeachievedonlywhenCTLA-4 a primary tumor, through cryoablation, TRAMPC2tumorswereimplantedonthe
blockade is combined with immunothera- would further improve the generation a left flank of male mice and cryoablated
pies such as those that induce increased systemic immune response that would when they reached about 5–8 mm in
antigen uptake and presentation on MHC result in the eradication of metastatic diameter. The mice were then treated
Class I molecules (a process called “cross- disease.9 The possibility of combining with anti-CTLA-4 and rechallenged with a
presentation”) by professional antigen- anti-CTLA-4 therapy with cryotherapy second inoculation of TRAMP C2 on the
presenting cells (APCs). These types of is appealing because of the low mor- opposite flank. Strikingly, in mice that
therapies include GM-CSF secreting bidity and cost-effectiveness of such an received both anti-CTLA-4 and cryoabla-
whole tumor cell vaccines,5 radiation6 or ablative technique compared with surgical tion, the number of SPAS-1-specific CD8+
a FLT-ligand expressing vaccine.7 It is interventions. T cells per mg of tumor was significantly
reasonable to hypothesize that in humans, UsingthetransplantableTRAMPmodel increased compared with control mice.
similarcombinationtherapiesadministered of mouse prostate cancer, we developed a Furthermore, the SPAS-1-specific T cells
*Correspondenceto:RebeccaWaitz;Email:[email protected]
Submitted:01/18/12;Accepted:01/21/12
http://dx.doi.org/10.4161/onci.19442
544 OncoImmunology Volume1Issue4
AUTHOR'SVIEW
© 2012 Landes Bioscience.
Do not distribute.
Figure1.Forfigurelegend,seepage546.
www.landesbioscience.com OncoImmunology 545
Figure1(Seepreviouspage).CryoablationneedstobecombinedwithCTLA-4blockadetogeneratesystemicimmunityofsufficientstrengthto
rejectasecondarytumor.(A)AprimaryTRAMPC2tumorisinoculatedintotheleftflankofamouseandallowedtogrowuntilitislargeenoughto
cryoablate.Ourmodelproposesthatcryoablationresultsinthereleaseofantigens,whicharetakenupbyantigenpresentingcells(cross-presentation).
InthepresenceofCTLA-4blockade,SPAS-1specificTcellsmaximallyproliferateinresponsetopositivesignalsdeliveredbytheengagementofTcell
receptorwithSPAS-1peptide/MHCIcomplexandCD28withB7.Thisenhancedproliferationresultsintherejectionofasecondaryrightflanktumor.
(B)IntheabsenceofCTLA-4blockade,CTLA-4dampensTcellproliferationandasecondtumorgrowsuncontrolled.(C)Inabsenceofcryoablation,
diminishedantigencross-presentationresultsinlimitedcross-primingofSPAS-1specificTcells.EveninthepresenceCTLA-4blockade,proliferation
ofSPAS-1specificTcellsisinsufficienttomediaterejectionofthetumor.
were enriched in the spleens of the mice highly infiltrated by effector T cells and effectivetreatmentstocombinewithCTLA-
receivingthecombinationtreatment,indic- the ratio of effector to T regulatory cell 4 blockade and we speculate that cryoabla-
ating the induction of a systemic tumor- was high. Furthermore, CD8+ T cells were tion synergizes with CTLA-4 blockade by
specific immune response. Importantly, important for tumor rejection as their augmenting antigen cross-presentation.
the combination of anti-CTLA-4 in vivo depletion resulted in a decreased effect of Another possible mechanism is that while
blockade and cryoablation also resulted in thecombinationtherapy. a growing intact tumor is likely to have a
improved survival and in an increased Although the full mechanism of tumor low level of antigen release in the absence
percentage of secondary tumor rejection. immunity in our model has not been of cryoablation, removal of the primary
Examination of secondary tumors by his- elucidated, it likely involves the exertion tumor may result in the removal of a
tology and flow cytometry revealed that, of effector function of TRAMP-specific systemic immune suppressive environ-
compared with controls, tumors from T cells after their activation by activated ment. While future studies will delineate
combination treated mice exhibited a shift APCs. Neither cryoablation nor CTLA-4 the mechanisms by which cryoablation
© 2012 Landes Bioscience.
from an immunologically hostile micro- blockade on their own were sufficient to cooperates with CTLA-4 blockade to
environment with few CD4+ and CD8+ mediate rejection of secondary tumors generate systemic immunity, our current
T cells and a low effector to T regulatory (Fig.1).Therapiessuchasvaccines,chemo- work provides evidence that this com-
cell ratio to an immunologically permis- therapies, and radiotherapy that improve bination therapy may improve survival in
sive microenvironment where tumors were antigen cross-presentation may be the most patients with metastatic disease.
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