Since acute myeloid leukemia (AML) is characterized by the blockade of hematopoietic differentiation and cell death, we interrogated RIPK3 signaling in AML development. Genetic loss of Ripk3 converted murine FLT3-ITD-driven myeloproliferation into an overt AML by enhancing the accumulation of leukemia-initiating cells (LIC). Failed inflammasome activation and cell death mediated by tumor necrosis factor receptor caused this accumulation of LIC exemplified by accelerated leukemia onset in Il1r1(-/-), Pycard(-/-), and Tnfr1/2(-/-) mice. RIPK3 signaling was partly mediated by mixed lineage kinase domain-like. This link between suppression of RIPK3, failed interleukin-1β release, and blocked cell death was supported by significantly reduced RIPK3 in primary AML patient cohorts. Our data identify RIPK3 and the inflammasome as key tumor suppressors in AML.

Evasion of programmed cell death represents a critical form of oncogene addiction in cancer cells. Understanding the molecular mechanisms underpinning cancer cell survival despite the oncogenic stress could provide a molecular basis for potential therapeutic interventions. Here we explore the role of pro-survival genes in cancer cell integrity during clonal evolution in non-small cell lung cancer (NSCLC). We identify gains of MCL-1 at high frequency in multiple independent NSCLC cohorts, occurring both clonally and subclonally. Clonal loss of functional TP53 is significantly associated with subclonal gains of MCL-1. In mice, tumour progression is delayed upon pharmacologic or genetic inhibition of MCL-1. These findings reveal that MCL-1 gains occur with high frequency in lung adenocarcinoma and can be targeted therapeutically.

T lymphocyte non-Hodgkin's lymphoma (T-NHL) represents an aggressive and largely therapy-resistant subtype of lymphoid malignancies. As deregulated apoptosis is a frequent hallmark of lymphomagenesis, we analyzed gene expression profiles and protein levels of primary human T-NHL samples for various apoptotic regulators. We identified the apoptotic regulator MCL-1 as the only pro-survival BCL-2 family member to be highly expressed throughout all human T-NHL subtypes. Functional validation of pro-survival protein members of the BCL-2 family in two independent T-NHL mouse models identified that the partial loss of Mcl-1 significantly delayed T-NHL development in vivo. Moreover, the inducible reduction of MCL-1 protein levels in lymphoma-burdened mice severely impaired the continued survival of T-NHL cells, increased their susceptibility to chemotherapeutics and delayed lymphoma progression. Lymphoma viability remained unaffected by the genetic deletion or pharmacological inhibition of all alternative BCL-2 family members. Consistent with a therapeutic window for MCL-1 treatment within the context of the whole organism, we observed an only minimal toxicity after systemic heterozygous loss of Mcl-1 in vivo. We conclude that re-activation of mitochondrial apoptosis by blockade of MCL-1 represents a promising therapeutic strategy to treat T-cell lymphoma.