Biology subjects

Zumbo, P.

Publications and source records attributed to Zumbo, P..

22 records · Page 2Linked to original sources

bioRxiv2021

A lineage-specific epigenetic memory of inflammation potentiates Kras-driven pancreatic tumorigenesis

Inflammation is essential to the disruption of tissue homeostasis, and, in the pancreas, can destabilize the identity of terminally differentiated acinar cells. Herein we employ lineage-traced mouse models to delineate the chromatin dynamics that accompany the cycle of metaplasia and regeneration following pancreatitis, and unveil the presence of an epigenetic memory of inflammation in the pancreatic acinar cell compartment. We observe that despite histologic resolution of pancreatitis, acinar cells fail to return to their molecular baseline after several months, representing an incomplete cell fate decision. In vivo, this epigenetic memory controls lineage plasticity, with diminished metaplasia in response to a second inflammatory insult but increased tumorigenesis with an oncogenic Kras mutation. We demonstrate that both persistent chromatin and transcriptional changes constituting memory are recalled with oncogenic stress. Together, our findings define the dynamics and recall of an epigenetic memory of inflammation that impacts cell fate decisions in a context-dependent manner.

cancer biology↗

bioRxiv2021

Immunogenicity of a public neoantigen derived from mutated PIK3CA

Public neoantigens (NeoAgs) represent an elite class of shared cancer-specific epitopes derived from recurrent mutations in driver genes that are restricted by prevalent HLA alleles. Here, we report on a high-throughput platform combining single-cell transcriptomic and T cell receptor (TCR) sequencing to establish whether mutant (Mut) PIK3CA, among the most common genomically altered driver oncogenes, generates an immunogenic public NeoAg. Using this method, we developed a library of TCRs that recognize an endogenously processed neoepitope containing a common PIK3CA hotspot mutation that is restricted by HLA-A*03:01. Mechanistically, immunogenicity to this public NeoAg arises primarily from enhanced stability of the neopeptide/HLA complex caused by a preferred HLA anchor substitution. Structural studies indicated that the HLA-bound neopeptide presents a relatively "featureless" surface dominated by the peptides backbone. To overcome the challenge of binding such an epitope with high specificity and affinity, we discovered that a lead TCR clinical candidate engages the neopeptide through an extended interface aided by an unusually long {beta}-chain complementarity-determining region 3 (CDR3{beta}) loop. In a pan-cancer cohort of patients with diverse malignancies that express the PIK3CA public NeoAg, we observed spontaneous immunogenicity, NeoAg clonal conservation, and in a limited number of cases, evidence of targeted immune escape. Together, these results establish the immunogenic potential of Mut PIK3CA, creating a framework for off-the-shelf immunotherapies targeting this public NeoAg.

immunology↗

bioRxiv2020

Selective BCL-XLAntagonists Eliminate Infected Cells from a Primary Cell Model of HIV Latency but not from Ex Vivo Reservoirs

HIV persists, despite antiviral immune responses and effective antiretroviral therapy, in viral reservoirs that seed rebound viremia if therapy is interrupted. Previously, we showed that the BCL-2 protein contributes to HIV persistence by conferring a survival advantage to reservoir-harboring cells. Here, we demonstrate that many of the BCL-2 family members are overexpressed in HIV-infected CD4+ T-cells, indicating increased tension between pro-apoptotic and pro-survival family members - as well as raising the possibility that the inhibition of pro-survival members may disproportionately affect the survival of HIV-infected cells. Based on these results, we chose to further study BCL2L1 (encoding the protein BCL-XL), due to its consistent overexpression and the availability of selective antagonists. Infection of primary CD4+ T-cells with either a clinical isolate, a CCR5-tropic strain, or a CXCR4-tropic strain of HIV resulted in increased BCL-XL protein expression; and treatment with two selective BCL-XL antagonists, A-1155463 and A-1551852, led to disproportionate cell death compared to uninfected CD4+ T-cells. In a primary cell model of latency, both BCL-XL antagonists drove significant reductions in total HIV DNA and in infectious cell frequencies both alone and in combination with the latency reversing agent bryostatin-1, with little off-target cytotoxicity. However, these antagonists, with or without bryostatin-1, or in combination with the highly potent latency reversing agent combination PMA + ionomycin, failed to reduce total HIV DNA and infectious reservoirs in ex vivo CD4+ T-cells from ART-suppressed donors. Our results add to growing evidence that bonafide reservoir-harboring cells are resistant to multiple "kick and kill" modalities - relative to latency models - and uncover BCL-XL antagonists as a facile approach to probing mechanistic underpinnings. We also interpret our results as encouraging of further exploration of BCL-XL antagonists for cure, where combination approaches may unlock the ability to eliminate ex vivo reservoirs.

microbiology↗

bioRxiv2020

Unacylated ghrelin and AZP531 suppress the 3D growth of breast cancers

Breast cancer is the most common type of cancer in women and notwithstanding important therapeutic advances, it remains the second leading cause of cancer-related death in the US. Despite extensive research relating to the hormone ghrelin, responsible for the stimulation of growth hormone release and appetite, little is known of the effects of its unacylated form, especially in cancer. One major area of research relates to its reported effects to increase insulin sensitivity in diabetics, this being the basis for the development of unacylated ghrelin analog, AZP531 or livoletide, now in clinical trials for the treatment of Prader-Willi Syndrome. The mechanism of action of unacylated ghrelin is largely uncharacterized, in any system, because it does not bind to or activate the cognate ghrelin receptor, GHSR1a. The present study aimed to characterize effects of unacylated ghrelin on breast cancer cells, define its mechanism of action, and explore the therapeutic potential of unacylated ghrelin or analog AZP531. We report potent effects of unacylated ghrelin, at picomolar doses, on the growth of breast cancer cells, dependent on 3D culture and activation of Gi. Suppression of MAPK signaling by unacylated ghrelin leads to cell cycle arrest and apoptosis. AZP531 also suppresses the growth of breast cancer cells in vitro and in xenografts, and may be a novel approach for the safe and effective treatment of breast cancer.

cancer biology↗