Identification of patient-specific and tumor-shared T cell receptor sequences in renal cell carcinoma patients

A major requirement for cancer immunotherapy is the development of biomarkers for prognosis and for monitoring therapy response. In an attempt to evaluate the immune response of renal cell carcinoma (RCC) patients, tumor lesions and / or blood samples from 12 RCC patients underwent deep T cell receptor (TCR) sequencing. Despite the low number of samples, different TCR distribution patterns could be detected. Most of the RCC patients presented "patient-specific" TCR sequences, and those clonotypes were present at higher frequency in tumor lesions suggesting a specific extravasation from the blood. Comparison among the tumor samples revealed also "patient-shared" TCR patterns. Indeed, a central core of 16 different TCRs were shared by 3 patients, whereas other 6 patients shared between 4 and 6 TCR sequences, with two sub-groups sharing 12 to 17 different clonotypes. The relative frequencies of shared clonotypes were very different varying from < 1% to a maximum of 37% of the total TCR repertoire. These data confirm the presence of tumor-specific TCR within the cancer tissue and suggest the existence of shared epitopes among different patients that might be used as targets for tumor immunotherapy.

Reduced immunosuppressive properties of axitinib in comparison with other tyrosine kinase inhibitors

The multikinase inhibitors sunitinib, sorafenib, and axitinib have an impact not only on tumor growth and angiogenesis, but also on the activity and function of immune effector cells. In this study, a comparative analysis of the growth inhibitory properties and apoptosis induction potentials of tyrosine kinase inhibitors on T cells was performed. Tyrosine kinase inhibitor treatment resulted in a dramatic decrease in T cell proliferation along with distinct impacts on the cell cycle progression. This was at least partially associated with an enhanced induction of apoptosis although triggered by distinct apoptotic mechanisms. In contrast to sunitinib and sorafenib, axitinib did not affect the mitochondrial membrane potential (Δψm) but resulted in an induction or stabilization of the induced myeloid leukemia cell differentiation protein (Mcl-1), leading to an irreversible arrest in the G2/M cell cycle phase and delayed apoptosis. Furthermore, the sorafenib-mediated suppression of immune effector cells, in particular the reduction of the CD8(+) T cell subset along with the down-regulation of key immune cell markers such as chemokine CC motif receptor 7 (CCR7), CD26, CD69, CD25, and CXCR3, was not observed in axitinib-treated immune effector cells. Therefore, axitinib rather than sorafenib seems to be suitable for implementation in complex treatment regimens of cancer patients including immunotherapy.

Abstract 2172: Effects of RAD001 on the protein expression pattern and function of tumor and immune cells

The crucial role of the PI3K/Akt/mTOR pathway in the pathogenesis of cancer has led to the development of various therapeutics targeting this signaling cascade. The serine/threonine kinase mTOR is involved in the regulation of the different growth properties of both tumor and immune cells. Furthermore, mTOR forms two macromolecular complexes: (i) the rapamycin-sensitive mTORC1, which contains RAPTOR and (ii) mTORC2, which is rapamycin-insensitive and contains RICTOR. Downstream targets of these complexes like HIF-1alpha and HIF-2alpha or cyclin D1 are responsible for the activation of various intracellular processes leading to the activation of cell proliferation, induction of angiogenesis, and metastasis. The effects of mTOR inhibitors have been most studied in T cells, although recently it has been shown that renal cell carcinoma (RCC) is tightly controlled by mTOR and that mTOR pathway activation represents an adverse prognostic factor. Thus targeted inhibition of mTOR represents a promising therapeutic approach for the treatment of RCC patients. Since it is currently discussed whether the RAD001-mediated effect on T cells might negatively interfere with its anti-tumoral activity in RCC we here analyzed the effects of RAD001 on the immune cell repertoire as well as the growth properties and protein expression pattern of RCC cells. We could show a decrease in the frequency of T cells which was associated with an altered expression of chemokines/ chemokine receptors suggesting an altered T cell homing. Furthermore, RAD001 exerts a dose-dependent growth inhibitory effect in RCC cells. This was accompanied by distinct expression levels of various proteins in RCC cells. So far, 11 differentially expressed proteins were identified by MALDI-TOF analysis, which are involved in cell proliferation and gene regulation. Currently functional analysis of RAD001-regulated proteins in T lymphocytes and RCC cells are performed providing better insights into the consequences of the mTOR inhibition.

Citation Format: Franziska Stehle, Kristin Schulz, Jana Kalich, Corinna Fahldieck, Barbara Seliger. Effects of RAD001 on the protein expression pattern and function of tumor and immune cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2172. doi:10.1158/1538-7445.AM2013-2172

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.