Abstract B11: Hyperthermia and antitumor immunity
Authors: Milani Valeria , Buecklein Veit , Issels Rolf Dieter 
Published: January 2011

Background: A phase III randomised EORTC trial combining systemic chemotherapy and regional hyperthermia (RHT) for patients (n=341) with locally-advanced high-risk soft tissue sarcoma (STS) showed that – compared to chemotherapy alone – the addition of RHT yields a statistically significant improvement in tumor response, with doubling of disease free and local progression free survival (ASCO 2007). A phase II study in chemo-pretreated patients with STS receiving 2nd line ICE chemotherapy (ifosfamide + carboplatin + etoposide) showed clinical activity with no further toxicity if combined with RHT (ASCO 2009).

The biological rationale of this approach is based on the direct cytotoxicity of heat and its chemosensitizing effect on tumor cells. Cells respond to heat by producing increasing amounts of molecular chaperones (heat shock proteins, HSPs). Some HSPs, in particular HSP70, are heat-inducible and are released by necrosis, where outside the cells they gain potent immunostimulatory functions. We provided strong evidence that heat up-regulated expression of HSP70 correlates with enhanced susceptibility to NK cell lysis of tumor cells. Besides recognizing of HSP70 on tumors as a target structure, it has been shown that NK cells can be activated ex vivo by the HSP70-derived 14-mer peptide (TKD), enhancing NK immune function. A phase I clinical study showed that reinfusion of autologous NK cells activated ex vivo by TKD in patients with advanced disease is well tolerated, feasible and initiates cytolytic activity of NK cells. In summary, this is a strong rationale that hyperthermia might have a positive impact on the immune system within the context of the heat shock response. We are implementing a prospective randomised study that investigates the impact of autologous TKD-activated NK cells adoptively transferred in patients with high-risk STS responding to chemotherapy and RHT. In a preliminary study we investigated the number and lytic activity of NK cells in patients with high-risk STS.

Patients and methods: Patients at primary diagnosis were scheduled to receive an anthracyclin and ifosfamide-based first-line chemotherapy and RHT; patients with progressive disease were scheduled to receive a 2nd line regimen (ICE) and RHT. Informed consent was obtained from all patients. Blood samples taken before the start of therapy were investigated for changes in lymphocyte subpopulations and for their lytic activity cells before and after therapy.

Results: Between April 2007 and December 2008 7 1st-line and 14 2nd-line patients were enrolled. 1. A progressive reduction in absolute NK cell counts but no relevant changes in total lymphocyte counts were observed over the applied cycles in second-line patients. 2. Whereas NK mediated lytic activity against K562 is detectable in healthy donors, the spontaneous NK cell activity in all but one second-line patients was completely abrogated at the start of the therapy and was not restored over 4 cycles of ICE+RHT. 3. First-line patients also showed a significant decrease in NK cell activity compared to healthy donors 4. In vitro stimulation of patients' NK cells with IL-2/TKD induced a highly significant increase in NK cell activity against K562 cells in first- and second-line patients, indicating that NK cells preserve their ability to be activated in vitro. Most interestingly, this ability persisted over the applied cycles of thermochemotherapy.

Conclusions: STS patients have suppression of NK cell activity but this lytic activity can be repristinated in vivo after stimulation with TKD/IL-2. Translational studies are performed to further elucidate the potential role of hyperthermia in promoting an antitumor immune response.

Citation Information: Clin Cancer Res 2010;16(7 Suppl):B11