Cancer/testis antigens in non small cell lung cancer : expression and immunogenicity

Lung cancer is the leading cause of cancer-related mortality in the world, whereby
Non Small Cell Lung Carcinomas (NSCLC) constitute 80% of all lung tumors.
Whereas in Stage I and II NSCLC surgical resection with or without adjuvant
chemotherapy currently represents the most frequently applied treatment, in late
stage NSCLC, representing 70% of all cases, chemotherapy or radiotherapy are
mainly palliative. Thus, the poor prognosis and the limited therapeutic options
available urge the development of new approaches. Among these, active specific
immunotherapy targeting Cancer/Testis Antigens (CTA) might represent a valuable
additional treatment in NSCLC.
CTA have been shown to represent promising targets in different types of cancer as
they are silent in healthy adult tissues except in testis and placenta. These tissues do
not present antigenic epitopes as they are deficient in MHC expression. Moreover,
CTA are expressed by various tumors of different histology, stage and grade, and in
some tumors, expression has been found to be correlated with poor disease specific
survival.
In this study first the prevalence and expression patterns of several CTA (MAGE-A1,
-A2, -A3, -A4, -A10, -A12 and NY-ESO-1) in freshly excised NSCLC were
investigated at gene and protein level. Tumor specimens (12 adeno-, 17 squamous
cell and 4 large cell carcinomas) were obtained from HLA-A*0101 and/or
HLA-A*0201 positive patients. CTA expression was detected in five adeno-, eight
squamous cell and in two large cell carcinoma samples (45.5%). MAGE-A10 and
-A12 were the most frequently (10/15 and 12/15 specimens, respectively) and
MAGE-A1, -A4 and NY-ESO-1 the least frequently expressed genes (6/15, 6/15 and
4/15 specimens, respectively). In 10/15 positive cases at least four CTA genes were
concomitantly expressed. These results at gene level were widely confirmed by
protein detection, the few discrepancies being explained by focal CTA expression
limited to defined tumor areas.
Immune responsiveness towards MAGE-A1 and -A3 (HLA-A*0101 restricted),
MAGE-A4, -A10, multi-MAGE-A (an epitope shared by several MAGE-A antigens)
and NY-ESO-1 (HLA-A*0201 restricted) epitopes was evaluated in cancer patients to
assess whether a specific cellular response could be detected or generated upon ex
vivo stimulation. Induction of CTL was performed on expanded CD8+ T lymphocytes
infiltrating the tumors (TIL), possibly enriched in activated specific T cells, eventually
due to the presence of antigen. After successful expansion, CD8+ cells were
repeatedly stimulated with autologous mature IL-4-DC pulsed with CTA peptides
and/or infected with a recombinant vaccinia virus (rVV) encoding the corresponding
epitopes together with the gene encoding human CD80. These vectors were
constructed during the present study to provide highly effective immunogenic
reagents with the perspective of possible clinical application.
CTA specific CTL response could be observed in 7/26 populations. In six cultures,
cytotoxic activity was low and did not correlate with expression of specific CTA in the
original tumor specimens. These CTL responses could possibly be attributed to a
primary in vitro sensitization. However, in one case stimulation of TIL with rVV
infected APC revealed a high level of MAGE-A10 specific CTL response detectable
by cytotoxicity assays and multimer staining. The corresponding gene, encoding the
target epitope, was highly expressed in the original tumor.
In NSCLC, CTA specific CTL sensitization in TIL, as detectable upon repeated
stimulation with a panel of well defined peptides and highly effective APC, is rare. On
the other hand, strong CTA specific CTL responses could frequently be generated
from peripheral blood lymphocyes of healthy donors, upon stimulation of large
numbers of effector cells with antigen pulsed DC obtained by GM-CSF/IFNα
induction.
The concomitant expression of multiple CTA in NSCLC and the possibility of natural
CTL responses in these cancers may support the development of specific
vaccination protocols using multi antigen vaccine preparations of CTA.