Smith, David

Abstract Autologous stem cell transplantation (ASCT) remains an important consolidation treatment for multiple myeloma (MM) patients, even in the era of novel agents. The prolongation of plateau-phase induced by ASCT is generally attributed to intensive cytoreduction. However, ASCT generates inflammation and profound lymphodepletion, which may result in hitherto unexpected immunological effects. To investigate potential immunological contributions to myeloma control after ASCT, we developed preclinical models of transplantation for MM using Vk*MYC myeloma that generates bony lytic lesions, a serum M band and marrow plasmacytosis that are hallmarks of clinical disease. Myeloma-bearing B6 recipients underwent myeloablative conditioning and were transplanted with naïve B6 bone marrow (BM) grafts with or without T cells from donors that were myeloma-naïve (SCT) or had low M bands at the time of harvest to mimic ASCT. Surprisingly, we demonstrate the broad induction of T cell-dependent myeloma control with enhanced median survival in recipients of grafts containing T cells compared to T cell depleted (TCD) BM alone (SCT= 91 days and ASCT > 100 days post-transplant vs TCD BM alone= 44 days; p<0.0001). Myeloma was most efficiently controlled when recipients were transplanted with memory T cells (CD44+) from autologous grafts (median survival: ASCT-CD44+ T cells >90 days post-transplant vs. CD44─ T cells = 50 days; p = 0.0006). Importantly, T cells adoptively transferred from recipients surviving > 120 days (MM-primed) protected secondary recipients compared to T cells from naïve donors (median survival: MM-primed > 120 days post-transplant vs 65 days naïve T cells; p = 0.0003). Furthermore, MM-primed CD8 T cells were restricted in TCR repertoire and provided protection in a myeloma clone-specific fashion, indicative of a tumor-specific T cell response. Despite this immune-mediated control of myeloma after SCT, progression still occurred in the majority of recipients. We phenotyped CD8+ T cells from the BM of MM-relapsed, MM-controlled and MM-free (that had never seen myeloma) mice 8 weeks after SCT. Expression of the inhibitory receptors, programmed cell death protein 1 (PD-1) and T cell immunoreceptor with Ig and ITIM domains (TIGIT) on BM CD8+ T-cells strongly correlated with myeloma cell number (r = 0.729, p<0.0001 and r = 0.796, p<0.0001 respectively). Additionally, the co-stimulatory/adhesion receptor CD226 (DNAM-1) was markedly downregulated as myeloma progressed (r = - 0.865, p<0.0001), as was interferon-γ secretion (r = - 0.76, p = 0.0022). t-SNE analysis confirmed an irreversible exhaustion signature at myeloma progression, characterized by the absence of DNAM-1 and co-expression of PD-1, TIM-3, TIGIT together with CD101 and CD38. Immune-checkpoint inhibition (CPI) early post-SCT, using antibodies against PD-1 or TIGIT facilitated long-term myeloma control (median survival in both treatment arms > 120 days post-SCT vs. 60 and 68 days respectively; p <0.05). Furthermore, TIGIT blockade limited CD8+ T cell exhaustion, increased CD107a and IFNγ secretion and expanded a memory CD8+ T cell population in the BM. Genetic deletion of either IFNγ or the IFNγ receptor from the donor graft resulted in dramatic myeloma progression after SCT. Consequently, treatment with a CD137 (4-IBB) agonist early after SCT profoundly augmented CD8+IFNγ+GranzymeB+ T-cell expansion in the BM, such that majority of treated animals eliminated myeloma and survived long-term. These data provide insights into an unappreciated mechanism of action of ASCT whereby myeloma immune-equilibrium is established and suggest that combination with immunotherapeutic strategies is a rational approach to generate long term disease control. Disclosures Smyth: Bristol Myers Squibb: Other: Research agreement; Tizona Therapeutics: Research Funding.

Immunotherapy holds promise for patients with multiple myeloma (MM), but little is known about how MM-induced immunosuppression influences response to therapy. Here, we investigated the impact of disease progression on immunotherapy efficacy in the Vk*MYC mouse model. Treatment with agonistic anti-CD137 (4-1BB) mAbs efficiently protected mice when administered early but failed to contain MM growth when delayed more than 3 weeks after Vk*MYC tumor cell challenge. The quality of the CD8 + T cell response to CD137 stimulation was not altered by the presence of MM, but CD8 + T cell numbers were profoundly reduced at the time of treatment. Our data suggest that an insufficient ratio of CD8 + T cells to MM cells (CD8/MM ratio) accounts for the loss of anti-CD137 mAb efficacy. We established serum M-protein levels prior to therapy as a predictive factor of response. Moreover, we developed an in silico model to capture the dynamic interactions between CD8 + T cells and MM cells. Finally, we explored two methods to improve the CD8/MM ratio: anti-CD137 mAb immunotherapy combined with Treg depletion or administered after chemotherapy treatment with cyclophosphamide or melphalan efficiently reduced MM burden and prolonged survival. Together, our data indicate that consolidation treatment with anti-CD137 mAbs might prevent MM relapse.

DNA viruses are known to be associated with a variety of different cancers. Human papillomaviruses (HPV) are a family of viruses and several of its sub-types are classified as high-risk HPVs as they are found to be associated with the development of a number of different cancers. Almost all cervical cancers appear to be driven by HPV infection and HPV is also found in most cancers of the anus and at least half the cancers of the vulva, penis and vagina, and increasingly found in one sub-type of head and neck cancers namely oropharyngeal squamous cell carcinoma. Our understanding of HPVs role in cancer development comes from extensive studies done on cervical cancer and it has just been assumed that HPV plays an identical role in the development of all other cancers arising in the presence of HPV sequences, although this has not been proven. Most invasive cervical cancers have the HPV genome integrated into one or more sites within the human genome. One powerful tool to examine all the sites of HPV integration in a cancer but that also provides a comprehensive view of genomic alterations in that cancer is the use of next generation sequencing of mate-pair libraries produced from the DNA isolated. We will describe how this powerful technology can provide important information about the genomic organization within an individual cancer genome, and how this has demonstrated that HPVs role in oropharyngeal squamous cell carcinoma is distinct from that in cervical cancer. We will also describe why the sequencing of mate-pair libraries could be a powerful clinical tool for the management of patients with a DNA viral etiology and how this could quickly transform the care of these patients.