AC inhibitors(University of Minnesota)

Acute myeloid leukemia (AML) is an aggressive, heterogenous disease characterized by clonal expansion of immature myeloid blasts. For the last five decades, intensive induction chemotherapy was the primary treatment option for AML. The 5-year survival rate for younger patients following induction chemotherapy is 40%-50%, which is far superior to the dismal 10%-15% 5-year survival seen in older adult patients, who constitute most AML cases. The specific Bcl-2 antagonist venetoclax was approved in combination with Ara-C or azacitidine for newly diagnosed AML or older adult patients unable to tolerate intensive chemotherapy. However, responses are incomplete and relapse rates remain high, necessitating the development of novel treatment strategies to augment current therapies and improve outcomes. To this end, targeting dysregulated sphingolipid metabolism in AML shows promise. Once overlooked as mere structural membrane components, sphingolipids are now appreciated as important regulators of cell signaling and are involved in many hallmarks of cancer that are of critical importance in AML. Acid ceramidase (AC), a ceramide-catabolizing lipid hydrolase, is upregulated in AML and correlates with poorer patient survival. The breakdown of ceramide, a bona fide pro-death lipid, by AC promotes chemotherapeutic resistance and leukemic survival in part by upregulating Mcl-1, a known venetoclax resistance factor.

Our ongoing research aims to characterize the efficacy of venetoclax combined with AC inhibition in AML.

SACLAC, a ceramide analog and irreversible AC inhibitor, augmented venetoclax sensitivity and synergistically decreased cell viability and induced apoptosis in AML cell lines with de novo and acquired venetoclax resistance. Remarkably, combinatorial SACLAC and venetoclax treatment was quantitatively more synergistic than standard venetoclax-containing AML treatment regimens (venetoclax+Ara-C and venetoclax+azacitidine) by Bliss analysis in over 60% of primary patient samples tested in vitro. The SACLAC and venetoclax regimen was less toxic to normal peripheral blood mononuclear cells and bone marrow cells relative to leukemic samples and exhibited toxicity towards these normal cell types comparable to venetoclax+Ara-C and venetoclax+azacitidine. Mechanistically, combination treatment potently increased ceramides, synergistically disrupted mitochondrial membrane potential, and depleted several proteins that inhibit apoptosis, including XIAP and cIAP1.

Overall, these data provide the rationale for additional mechanistic and preclinical in-vivo studies targeting AC and Bcl-2 in AML.

Existing neuroprotective drugs are not effective enough to treat alcoholic encephalopathy. This makes the development of novel pharmacological approaches to treating patients with ethanol-induced neurodegeneration(EIN) relevant. Therefore, the search for new targets among intracellular signaling molecules of regeneration-competent cells of nervous tissue is promising.

This study aims to explore the involvement of cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) in the realization of the functions of nervous tissue progenitors and glial cells in EIN.

Experiments were conducted on mice of C57B1/6. EIN was modeled in vitro and in vivo. The effects of the adenylate cyclase (AC) and PKA inhibitors on the colony-forming capacity of neural stem cells (NSC) and neuronal-committed progenitors (NCP), their proliferative activity, and intensity of specialization were investigated. The secretion of neurotrophins by astrocytes, oligodendrocytes, and microglial cells was also evaluated. Individual fractions of cells were obtained using the immunomagnetic separation method.

The cAMP/PKA signaling is shown to stimulate the proliferation of the NSC and inhibit the mitotic activity of the NCP under the conditions of their optimal vital activity. cAMP reduces the specialization intensity of both types of progenitors. EIN leads to the inversion of the role of the cAMP/PKA-pathway in the regulation of NSC functions. cAMP-pathway has varying influences on the secretion of neurotrophic growth factors by glial cells depending on their living conditions. AC blockage stimulates the realization of the NSC and NCP growth potential and production of neurotrophins by astrocytes and microglial cells in EIN.

These findings show the potential for the use of AC inhibitors as novel effective drugs for the therapy of alcoholic encephalopathy.