Interferon-alpha modulates the immune response enhancing B7-1 and B7-2 costimulatory molecules and T8 lymphocytes in chronic myeloid leukemia

CDK4/6 inhibitors sensitize gammaherpesvirus-infected tumor cells to T-cell killing by enhancing expression of immune surface molecules

BACKGROUND

The two oncogenic human gammaherpesviruses, Kaposi sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), both downregulate immune surface molecules, such as MHC-I, ICAM-1, and B7-2, enabling them to evade T-cell and natural killer cell immunity. Both also either encode for human cyclin homologues or promote cellular cyclin activity, and this has been shown to be important for proliferation and survival of gammaherpesvirus-induced tumors. CDK4/6 inhibitors, which are approved for certain breast cancers, have been shown to enhance expression of MHC-I in cell lines and murine models of breast cancer, and this was attributed to activation of interferons by endogenous retrovirus elements. However, it was not known if this would occur in gammaherpesvirus-induced tumors in which interferons are already activated.

METHODS

Multiple KSHV/EBV-infected cell lines were treated with CDK4/6 inhibitors. The growth of viable cells and expression of surface markers was assessed. T cell activation stimulated by the treated cells was assayed by a T-cell activation bioassay. Both viral and host gene expression was surveyed using RT-qPCR.

RESULTS

Three CDK4/6 inhibitors, abemaciclib, palbociclib, and ribociclib, inhibited cell growth in KSHV-induced primary effusion lymphoma (PEL) and EBV positive Burkitt's lymphoma (BL) cell lines, and KSHV-infected human umbilical vein endothelial cells (HUVECs). Moreover, CDK4/6 inhibitors increased mRNA and surface expression of MHC-I in all three and prevented downregulation of MHC-I surface expression during lytic replication in KSHV-infected cells. CDK4/6 inhibitors also variably increased mRNA and surface expression of ICAM-1 and B7-2 in the tested lines. Abemaciclib also significantly enhanced T-cell activation induced by treated PEL and BL cells. Certain gammaherpesvirus genes as well as endogenous retrovirus (ERV) 3-1 genes were enhanced by CDK4/6 inhibitors in most PEL and BL lines and this enhancement was associated with expression of gamma interferon-induced genes including MHC-I.

CONCLUSIONS

These observations provide evidence that CDK4/6 inhibitors can induce expression of surface immune markers MHC-I, B7-2, and ICAM-1 in gammaherpesvirus-infected cell lines and induce virus-specific immunity. They can thus thwart virus-induced immune evasion. These effects, along with their direct effects on KSHV- or EBV-induced tumors, provide a rational for the clinical testing of these drugs in these tumors.

Treatment options for chronic myeloid leukemia: imatinib versus interferon versus allogeneic transplant

PURPOSE OF REVIEW

This review considers recent developments in the treatment of chronic myeloid leukemia with attention to current data evaluating the relative roles of imatinib mesylate, interferon-alpha, and allogeneic blood or marrow transplantation. Additionally, the review discusses advances in the basic understanding of the mechanisms by which these three different therapies function against chronic myeloid leukemia.

RECENT FINDINGS

Long-term follow-up has found that interferon-alpha was able to produce complete cytogenetic remission in15 to 25% of patients, with some of these patients achieving a molecular remission. Some patients who achieve a complete cytogenetic remission also achieve long-term disease-free survival and possibly cure. Imatinib has produced remarkable hematologic and cytogenetic responses in newly treated and in interferon-alpha-refractory patients, yet there are no long-term survival data at this point. Some laboratory findings imply that imatinib may primarily affect mature chronic myeloid leukemia progenitors and not chronic myeloid leukemia stem cells, leaving doubt that the improved rate of complete cytogenetic remissions will result in increased overall survival. Other clonal cytogenetic abnormalities have also been reported in the Philadelphia chromosome-negative cells present in complete cytogenetic remissions to imatinib. The use of donor lymphocytes infusion (DLI) continues to treat relapsed chronic myeloid leukemia effectively after allogeneic blood or marrow transplantation whereas the use of nonmyeloablative therapy has effectively reduced transplant-related mortality.

SUMMARY

Patients with chronic myeloid leukemia now have several potential treatment options from which to choose. Imatinib mesylate currently provides excellent hematologic and cytogenetic response rates with minimal toxicity. However, long-term data of efficacy is lacking. Emerging evidence that imatinib rarely leads to molecular complete remission and that many patients are still at risk of relapse and other clonal disorders is concerning and suggest the possibility that imatinib's early high response rates may not translate into survival advantage. Interferon-alpha continues to be effective therapy for many patients and, along with blood or marrow transplantation, is proved to prolong survival. The impacts of both are in part limited because of their toxicity profiles. Ongoing laboratory investigations and clinical trials remain paramount to providing the best treatment approach for our patients with chronic myeloid leukemia.