Interleukin-2 and cancer: critical analysis of results, problems and expectations

Non-linear relationship between soluble interleukin-2 receptor and prognosis of diffuse large B-cell lymphoma

Despite an emphasis on the prognostic impact of serum soluble interleukin-2 receptor (sIL-2R) at diagnosis in patients with diffuse large B-cell lymphoma (DLBCL), whether the prognostic impact of elevated sIL-2R is linear remains unclear. To verify the presence of a non-linear association between sIL-2R level at diagnosis and overall survival (OS) in patients with newly diagnosed DLBCL, we conducted a multi-center, observational retrospective study. Among 488 analyzable patients, Cox proportional hazards modeling identified serum sIL-2R level at diagnosis as an independent predictor of OS. Multivariate Cox hazard modeling with restricted cubic spline model demonstrated that the relationship between serum sIL-2R level and OS was clearly non-linear (P for effect of sIL-2R = 0.002; P for non-linearity = 0.015). Mortality risk increased gradually as sIL-2R levels increased and plateaued at approximately 5,000 U/mL. Segmented regression analysis revealed that the trend in negative prognostic impact from a gradual increase in serum sIL-2R level changed significantly, with a breakpoint at approximately 2,000 U/mL. Multivariate receiver operating characteristic curves showed a significant improvement in prediction ability when serum sIL-2R level was added to the International Prognostic Index (IPI). Serum sIL-2R level at diagnosis was not only a prognostic factor, but also improved predictive accuracy for OS when incorporated with the IPI. However, the negative correlation between increasing sIL-2R and prognosis was non-linear.

Interleukin-2 alters distribution of CD144 (VE-cadherin) in endothelial cells

BACKGROUND

High-dose IL-2 (HDIL2) is approved for the treatment of metastatic melanoma and renal cell carcinoma, but its use is limited in part by toxicity related to the development of vascular leak syndrome (VLS). Therefore, an understanding of the mechanisms that underlie the initiation and progression of HDIL2-induced increases in endothelial cell (EC) permeability leading to VLS are of clinical importance.

METHODS

We established a novel ex vivo approach utilizing primary human pulmonary microvascular ECs to evaluate EC barrier dysfunction in response to IL-2.

RESULTS

Complementary in vitro studies using exogenous IL-2 and ex vivo studies using serum from patients treated with IL-2 demonstrate that HDIL2 induces VLS through CD144 (vascular endothelial (VE)-cadherin) redistribution.

CONCLUSIONS

These findings provide new insight into how IL-2 induces VLS and identifies VE-cadherin as a potential target for preventing IL-2-related VLS.

Nullomer derived anticancer peptides (NulloPs): differential lethal effects on normal and cancer cells in vitro

We demonstrate the first use of the nullomer (absent sequences) approach to drug discovery and development. Nullomers are the shortest absent sequences determined in a species, or group of species. By identifying the shortest absent peptide sequences from the NCBI databases, we screened several potential anti-cancer peptides. In order to improve cell penetration and solubility we added short poly arginine tails (5Rs), and initially solubilized the peptides in 1M trehalose. The results for one of the absent sequences 9R (RRRRRNWMWC), and its scrambled version 9S1R (RRRRRWCMNW) are reported here. We refer to these peptides derived from nullomers as PolyArgNulloPs. A control PolyArgNulloP, 124R (RRRRRWFMHW), was also included. The lethal effects of 9R and 9S1R are mediated by mitochondrial impairment as demonstrated by increased ROS production, ATP depletion, cell growth inhibition, and ultimately cell death. These effects increase over time for cancer cells with a concomitant drop in IC-50 for breast and prostate cancer cells. This is in sharp contrast to the effects in normal cells, which show a decreased sensitivity to the NulloPs over time.

Enhanced local dendritic cell activity and tumor-specific immunoresponse in combined radiofrequency ablation and interleukin-2 for the treatment of human head and neck cancer in a murine orthotopic model

BACKGROUND

Radiofrequency ablation (RFA) is a minimally invasive tumor destruction technique and can provide the antigen source initiating tumor immunity. However, induced immune response is weak and requires additional immunotherapy for optimized RFA treatment against cancer.

METHODS

A murine orthotopic model of head and neck squamous cell carcinoma (HNSCC) was established to investigate the efficacy and mechanism of an RFA + interleukin-2 (IL-2) combination adenoviral gene therapy among 6 groups. Tumor volume change, apoptosis, in situ macrophage recruitment, cytotoxic T lymphocyte (CTL) activity, migration of dendritic cells into the regional lymph nodes, and systemic antitumor immunity were examined.

RESULTS

RFA + IL-2 therapy induced the highest levels of macrophage recruitment and dendritic cell migration resulting in enhanced CTL activity, increased tumor apoptosis, enhanced systemic antitumor immunity, and the best inhibition of tumor growth among all groups.

CONCLUSION

RFA + IL-2 combination therapy generates potent tumor immunity to suppress tumor growth in HNSCC.