Cancer immune therapy for myeloid malignancies: present and future

The myelodysplastic syndromes, the chronic myeloproliferative neoplasms, and the acute myeloid leukemia are malignancies of the myeloid hematopoietic stem cells of the bone marrow. The diseases are characterized by a dysregulation of the immune system as both the cytokine milieu, immune phenotype, immune regulation, and expression of genes related to immune cell functions are deregulated. Several treatment strategies try to circumvent this deregulation, and several clinical and preclinical trials have shown promising results, albeit not in the same scale as chimeric antigen receptor T cells have had in the treatment of refractory lymphoid malignancies. The use of immune checkpoint blocking antibodies especially in combination with hypomethylating agents has had some success-a success that will likely be enhanced by therapeutic cancer vaccination with tumor-specific antigens. In the chronic myeloproliferative neoplasms, the recent identification of immune responses against the Januskinase-2 and calreticulin exon 9 driver mutations could also be used in the vaccination setting to enhance the anti-tumor immune response. This immune response could probably be enhanced by the concurrent use of immune checkpoint inhibitors or by vaccination with epitopes from immune regulatory proteins such as arginase-1 and programmed death ligand-1. Herein, we provide an overview of current cancer immune therapeutic treatment strategies as well as potential future cancer immune therapeutic treatment options for the myeloid malignancies.

The calreticulin (CALR) exon 9 mutations are promising targets for cancer immune therapy

The calreticulin (CALR) exon 9 mutations are found in ∼30% of patients with essential thrombocythemia and primary myelofibrosis. Recently, we reported spontaneous immune responses against the CALR mutations. Here, we describe that CALR-mutant (CALRmut)-specific T cells are able to specifically recognize CALRmut cells. First, we established a T-cell culture specific for a CALRmut epitope. These specific T cells were able to recognize several epitopes in the CALRmut C terminus. Next, we established a CALRmut-specific CD4⁺ T-cell clone by limiting dilution. These CD4⁺ T cells recognized autologous CALRmut monocytes and hematopoietic stem cells, and T-cell recognition of target cells was dependent on the presence of CALR. Furthermore, we showed that the CALRmut response was human leukocyte antigen (HLA)-DR restricted. Finally, we demonstrated that the CALRmut-specific CD4⁺ T cells, despite their phenotype, were cytotoxic to autologous CALRmut cells, and that the cytotoxicity was mediated by degranulation of the T cells. In conclusion, the CALR exon 9 mutations are targets for specific T cells and thus are promising targets for cancer immune therapy such as peptide vaccination in patients harboring CALR exon 9 mutations.

Brentuximab vedotin for relapsed or refractory Hodgkin lymphoma: experience in Turkey

Current treatment modalities can cure up to 70–80 % of patients with classical Hodgkin lymphoma. Approximately, 20–30 % of patients require further treatment options. Brentuximab vedotin has been approved for the treatment of relapsed and refractory Hodgkin lymphoma. In the present study, we report the experience with brentuximab vedotin as single agent in 58 patients with relapsed or refractory Hodgkin lymphoma. The objective response rate was 63.5 % with 13 complete responders (26.5 %) among 49 patients evaluated at the early phase of treatment (2–5 cycles). Upon treatment prolongation (≥6 cycles), 37 patients achieved a final objective response rate of 32.4 % with 21.6 % of complete and 10.8 % of partial response. Overall survival at 12 months was 70.6 %, and progression-free survival at 12 months was 32.8 %. Median overall survival could not be reached and median progression-free survival was 7 months. While the median duration of response was 9 months in the whole cohort, it was 11.5 months in the complete responders. Complete response rates in patients treated with >3 chemotherapy regimens before brentuximab vedotin were significantly lower (p = 0.016). Fourteen patients were subsequently transplanted. In conclusion, brentuximab vedotin provided a bridge to transplantation in approximately one quarter of the patients. The declining response rates during the course of treatment suggest that transplantation should be implemented early during brentuximab vedotin treatment.