Depletion of preexisting B-cell lymphoma 2-expressing senescent cells before vaccination impacts antigen-specific antitumor immune responses in old mice.

The age-related decline in immunity reduces the effectiveness of vaccines in older adults. Immunosenescence is associated with chronic, low-grade inflammation, and the accumulation of senescent cells. The latter express Bcl-2 family members (providing resistance to cell death) and exhibit a pro-inflammatory, senescence-associated secretory phenotype (SASP). Preexisting senescent cells cause many aging-related disorders and therapeutic means of eliminating these cells have recently gained attention. The potential consequences of senescent cell removal on vaccine efficacy in older individuals are still ignored. We used the Bcl-2 family inhibitor ABT-263 to investigate the effects of pre-vaccination senolysis on immune responses in old mice. Two different ovalbumin (OVA)-containing vaccines (containing a saponin-based or a CpG oligodeoxynucleotide adjuvant) were tested. ABT-263 depleted senescent cells (apoptosis) and ablated the basal and lipopolysaccharide-induced production of SASP-related factors in old mice. Depletion of senescent cells prior to vaccination (prime/boost) had little effect on OVA-specific antibody and T-cell responses (slightly reduced and augmented, respectively). We then used a preclinical melanoma model to test the antitumor potential of senolysis before vaccination (prime with the vaccine and OVA boost by tumor cells). Surprisingly, ABT-263 treatment abrogated the vaccine's ability to protect against B16 melanoma growth in old animals, an effect associated with reduced antigen-specific T-cell responses. Some, but not all, of the effects were age-specific, which suggests that preexisting senescent cells were partly involved. Hence, depletion of senescent cells modifies immune responses to vaccines in some settings and caution should be taken when incorporating senolytics into vaccine-based cancer therapies.

Rapid disease progression on immune checkpoint inhibitors in young patients with stage IV melanoma.

Background: Immune checkpoint inhibitors (ICIs) are the standard of care for metastatic cutaneous melanoma (mCM) patients, but their efficacy in young adults aged less than 40 years remains unclear. Materials and methods: We retrospectively analyzed 303 stage IV melanoma patients of different ages treated with nivolumab, pembrolizumab, or ipilimumab plus nivolumab combination therapy. Clinical data and blood values such as LDH, CRP, and absolute immune cell counts were retrieved from the medical records. Pre-treatment serum concentrations of soluble immune checkpoint proteins were measured using ELISA. In addition, information on frequencies of various T cell subsets in the peripheral blood was collected from a previously reported study (ELEKTRA). Patient characteristics and clinical information was correlated with PFS and OS using univariate and multivariate cox regression analysis. Results: Of 303 patients, 33 (11%) were ≤ 40 years old. The older patients had a median age of 64 (95% CI: 61-66). Concerning prognostic parameters, there was no difference between the age groups, e.g., in gender, LDH, or the existence of brain or liver metastases. Patients aged ≤ 40 years [p = 0.014; HR: 1.6 (95% CI: 1.1-2.4)], presence of liver metastases [p = 0.016; HR: 1.4 (95% CI: 1.0-1.9)], line of ICI treatment [p = 0.009; HR: 1.4 (1.0-1.9)], elevated LDH [p = 0.076; HR: 1.3 (95% CI: 0.97-1.8)], and brain metastasis [p = 0.080; HR: 1.3 (95% CI: 0.97-1.7)], were associated with shorter PFS in univariate analysis. Multivariate analysis revealed that the patient's age (≤ 40 years) remains a high-risk factor upon adjusting for all potential confounders [p = 0.067; HR: 1.5 (95% CI: 0.97-2.3)]. Blood parameters revealed that patients ≤ 40 years have relatively higher frequencies of activated CD4 T cells (CD4 + Ki67 + CD4 + ICOS +) in the blood, and significantly lower number of basophils and CD45RA- memory T cells, compared to patients above 40 years (p < 0.05). In addition, patients ≤ 40 years experiencing disease progression within 6 months of ICI treatment had increased concentrations of sPDL1 (p = 0.05) and sTIM3 (p = 0.054) at baseline. Conclusion: Young patients with stage IV melanoma may experience shorter progression-free survival upon ICI treatment compared to patients above 40 years and are characterized by fewer basophils and memory T cells in the blood.