The therapeutic potential of targeting PI3K/AKT/PTEN signalling in B-cell malignancies remains attractive. Whilst PI3K-α/δ inhibitors demonstrate clinical benefit in certain B-cell lymphomas, PI3K signalling inhibitors have been inadequate in relapsed/refractory diffuse large B-cell lymphoma (DLBCL) in part, due to treatment related toxicities. Clinically, AKT inhibitors exhibit a differentiated tolerability profile offering an alternative approach for treating patients with B-cell malignancies. To explore how AKT inhibition complements other potential therapeutics in the treatment of DLBCL patients, an in vitro combination screen was conducted across a panel of DLCBL cell lines. The AKT inhibitor, capivasertib, in combination with the BCL-2 inhibitor, venetoclax, produced notable therapeutic benefit in preclinical models of DLBCL. Capivasertib and venetoclax rapidly induced caspase and PARP cleavage in GCB-DLBCL PTEN wildtype cell lines and those harbouring PTEN mutations or reduced PTEN protein, driving prolonged tumour growth inhibition in DLBCL cell line and patient derived xenograft lymphoma models. The addition of the rituximab further deepened the durability of capivasertib and venetoclax responses in a RCHOP refractory DLBCL in vivo models. These findings provide preclinical evidence for the rational treatment combination of AKT and BCL-2 inhibitors using capivasertib and venetoclax respectively alongside anti-CD20 antibody supplementation for treatment of patients with DLBCL.

• MeSH
• Apoptosis drug effects   MeSH
• Bridged Bicyclo Compounds, Heterocyclic * pharmacology   therapeutic use   MeSH
• Lymphoma, Large B-Cell, Diffuse * drug therapy   pathology   MeSH
• PTEN Phosphohydrolase metabolism   MeSH
• Humans MeSH
• Mice, SCID MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Cell Proliferation drug effects   MeSH
• Antineoplastic Combined Chemotherapy Protocols * pharmacology   therapeutic use   MeSH
• Proto-Oncogene Proteins c-akt * metabolism   MeSH
• Proto-Oncogene Proteins c-bcl-2 * antagonists & inhibitors   metabolism   MeSH
• Pyrimidines * pharmacology   therapeutic use   MeSH
• Pyrroles pharmacology   therapeutic use   MeSH
• Rituximab pharmacology   therapeutic use   MeSH
• Sulfonamides * pharmacology   therapeutic use   MeSH
• Xenograft Model Antitumor Assays * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• BCL2 protein, human MeSH Browser
• Bridged Bicyclo Compounds, Heterocyclic * MeSH
• capivasertib MeSH Browser
• PTEN Phosphohydrolase MeSH
• Proto-Oncogene Proteins c-akt * MeSH
• Proto-Oncogene Proteins c-bcl-2 * MeSH
• Pyrimidines * MeSH
• Pyrroles MeSH
• Rituximab MeSH
• Sulfonamides * MeSH
• venetoclax MeSH Browser

Besides many other mutations in known cancer driver genes, mantle cell lymphoma (MCL) is characterized by recurrent genetic alterations of important regulators of the phosphoinositol-3-kinase (PI3K) cascade including PIK3CA gains and PTEN losses. To evaluate the biological and functional consequences of these aberrations in MCL, we have introduced transgenic expression of PIK3CA (PIK3CA UP) and performed knockout/knockdown of PTEN gene (PTEN KO/KD) in 5 MCL cell lines. The modified cell lines were tested for associated phenotypes including dependence on upstream B-cell receptor (BCR) signaling (by an additional BCR knockout). PIK3CA overexpression decreased the dependence of the tested MCL on prosurvival signaling from BCR, decreased levels of oxidative phosphorylation, and increased resistance to 2-deoxy-glucose, a glycolysis inhibitor. Unchanged protein kinase B (AKT) phosphorylation status and unchanged sensitivity to a battery of PI3K inhibitors suggested that PIK3CA gain might affect MCL cells in AKT-independent manner. PTEN KO was associated with a more distinct phenotype: AKT hyperphosphorylation and overactivation, increased resistance to multiple inhibitors (most of the tested PI3K inhibitors, Bruton tyrosine kinase inhibitor ibrutinib, and BCL2 inhibitor venetoclax), increased glycolytic rates with resistance to 2-deoxy-glucose, and significantly decreased dependence on prosurvival BCR signaling. Our results suggest that the frequent aberrations of the PI3K pathway may rewire associated signaling with lower dependence on BCR signaling, better metabolic and hypoxic adaptation, and targeted therapy resistance in MCL.

• MeSH
• Drug Resistance, Neoplasm genetics   MeSH
• Molecular Targeted Therapy MeSH
• Class I Phosphatidylinositol 3-Kinases * genetics   metabolism   MeSH
• Phosphatidylinositol 3-Kinases metabolism   MeSH
• PTEN Phosphohydrolase * metabolism   genetics   MeSH
• Humans MeSH
• Lymphoma, Mantle-Cell * drug therapy   genetics   metabolism   MeSH
• Cell Line, Tumor MeSH
• Proto-Oncogene Proteins c-akt metabolism   MeSH
• Receptors, Antigen, B-Cell metabolism   MeSH
• Signal Transduction MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Class I Phosphatidylinositol 3-Kinases * MeSH
• Phosphatidylinositol 3-Kinases MeSH
• PTEN Phosphohydrolase * MeSH
• PIK3CA protein, human MeSH Browser
• Proto-Oncogene Proteins c-akt MeSH
• PTEN protein, human MeSH Browser
• Receptors, Antigen, B-Cell MeSH

Activated B-cell-like diffuse large B-cell lymphoma (ABC-DLBCL) is driven by aberrant activation of the B-cell receptor (BCR) and the TLR/MyD88 signaling pathways. The heat-shock protein HSP110 is a candidate for their regulation as it stabilizes MyD88. However, its role in overall BCR signaling remains unknown. Here, we used first-in-class HSP110 inhibitors to address this question. HSP110 inhibitors decreased the survival of several ABC-DLBCL cell lines in vitro and in vivo, and reduced the phosphorylation of BCR signaling kinases, including BTK and SYK. We identified an interaction between HSP110 and SYK and demonstrated that HSP110 promotes SYK phosphorylation. Finally, the combination of the HSP110 inhibitor with the PI3K inhibitor copanlisib decreases SYK/BTK and AKT phosphorylation synergistically, leading to suppression of tumor growth in cell line xenografts and strong reduction in patient-derived xenografts. In conclusion, by regulating the BCR/TLR signaling pathway, HSP110 inhibitors are potential drug candidates for ABC-DLBCL patients.

• MeSH
• Quinazolines MeSH
• Lymphoma, Large B-Cell, Diffuse * drug therapy   metabolism   pathology   MeSH
• Phosphorylation drug effects   MeSH
• Syk Kinase * antagonists & inhibitors   metabolism   MeSH
• Humans MeSH
• Mice, SCID MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Tumor Cells, Cultured MeSH
• HSP110 Heat-Shock Proteins * metabolism   MeSH
• Pyrimidines pharmacology   MeSH
• Receptors, Antigen, B-Cell * metabolism   MeSH
• Signal Transduction * drug effects   MeSH
• Xenograft Model Antitumor Assays * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Quinazolines MeSH
• copanlisib MeSH Browser
• Syk Kinase * MeSH
• HSP110 Heat-Shock Proteins * MeSH
• Pyrimidines MeSH
• Receptors, Antigen, B-Cell * MeSH
• SYK protein, human MeSH Browser

Venetoclax (VEN), a B-cell lymphoma 2 (BCL2) inhibitor, has a promising single-agent activity in mantle cell lymphoma (MCL), acute lymphoblastic leukemia (ALL), and large BCLs, but remissions were generally short, which call for rational drug combinations. Using a panel of 21 lymphoma and leukemia cell lines and 28 primary samples, we demonstrated strong synergy between VEN and A1155463, a BCL-XL inhibitor. Immunoprecipitation experiments and studies on clones with knockout of expression or transgenic expression of BCL-XL confirmed its key role in mediating inherent and acquired VEN resistance. Of note, the VEN and A1155463 combination was synthetically lethal even in the cell lines with lack of expression of the proapoptotic BCL2L11/BIM and in the derived clones with genetic knockout of BCL2L11/BIM. This is clinically important because BCL2L11/BIM deletion, downregulation, or sequestration results in VEN resistance. Immunoprecipitation experiments further suggested that the proapoptotic effector BAX belongs to principal mediators of the VEN and A1155463 mode of action in the BIM-deficient cells. Lastly, the efficacy of the new proapoptotic combination was confirmed in vivo on a panel of 9 patient-derived lymphoma xenografts models including MCL (n = 3), B-ALL (n = 2), T-ALL (n = 1), and diffuse large BCL (n = 3). Because continuous inhibition of BCL-XL causes thrombocytopenia, we proposed and tested an interrupted 4 days on/3 days off treatment regimen, which retained the desired antitumor synergy with manageable platelet toxicity. The proposed VEN and A1155463 combination represents an innovative chemotherapy-free regimen with significant preclinical activity across diverse BCL2+ hematologic malignancies irrespective of the BCL2L11/BIM status.

• MeSH
• Apoptosis drug effects   MeSH
• Benzothiazoles MeSH
• Bridged Bicyclo Compounds, Heterocyclic * pharmacology   therapeutic use   MeSH
• Drug Resistance, Neoplasm * MeSH
• Isoquinolines MeSH
• Humans MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• bcl-X Protein * metabolism   antagonists & inhibitors   MeSH
• Bcl-2-Like Protein 11 * metabolism   genetics   MeSH
• Antineoplastic Agents pharmacology   therapeutic use   MeSH
• Proto-Oncogene Proteins c-bcl-2 metabolism   antagonists & inhibitors   MeSH
• Sulfonamides * pharmacology   therapeutic use   MeSH
• Drug Synergism MeSH
• Xenograft Model Antitumor Assays MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• A-1155463 MeSH Browser
• BCL2L1 protein, human MeSH Browser
• Benzothiazoles MeSH
• Bridged Bicyclo Compounds, Heterocyclic * MeSH
• Isoquinolines MeSH
• bcl-X Protein * MeSH
• Bcl-2-Like Protein 11 * MeSH
• Antineoplastic Agents MeSH
• Proto-Oncogene Proteins c-bcl-2 MeSH
• Sulfonamides * MeSH
• venetoclax MeSH Browser

BACKGROUND: Despite recent advances in the treatment of aggressive lymphomas, a significant fraction of patients still succumbs to their disease. Thus, novel therapies are urgently needed. As the anti-CD20 antibody rituximab and the CD19-targeting antibody tafasitamab share distinct modes of actions, we investigated if dual-targeting of aggressive lymphoma B-cells by combining rituximab and tafasitamab might increase cytotoxic effects. METHODS: Antibody single and combination efficacy was determined investigating different modes of action including direct cytotoxicity, antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) in in vitro and in vivo models of aggressive B-cell lymphoma comprising diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma (BL). RESULTS: Three different sensitivity profiles to antibody monotherapy or combination treatment were observed in in vitro models: while 1/11 cell lines was primarily sensitive to tafasitamab and 2/11 to rituximab, the combination resulted in enhanced cell death in 8/11 cell lines in at least one mode of action. Treatment with either antibody or the combination resulted in decreased expression of the oncogenic transcription factor MYC and inhibition of AKT signaling, which mirrored the cell line-specific sensitivities to direct cytotoxicity. At last, the combination resulted in a synergistic survival benefit in a PBMC-humanized Ramos NOD/SCID mouse model. CONCLUSION: This study demonstrates that the combination of tafasitamab and rituximab improves efficacy compared to single-agent treatments in models of aggressive B-cell lymphoma in vitro and in vivo.

• Keywords
• CD19, CD20, antibody therapy, lymphoma, rituximab, tafasitamab, tumor immunology,
• MeSH
• Burkitt Lymphoma * drug therapy   MeSH
• Lymphoma, Large B-Cell, Diffuse * drug therapy   MeSH
• Antibodies, Monoclonal, Humanized MeSH
• Leukocytes, Mononuclear MeSH
• Mice, Inbred NOD MeSH
• Mice, SCID MeSH
• Mice MeSH
• Rituximab pharmacology   therapeutic use   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Antibodies, Monoclonal, Humanized MeSH
• Rituximab MeSH
• tafasitamab MeSH Browser

Multiple myeloma (MM) is an incurable, malignant B cell disorder characterized by frequent relapses and a poor prognosis. Thus, new therapeutic approaches are warranted. The phosphatidylinositol-3-kinase (PI3K) pathway plays a key role in many critical cellular processes, including cell proliferation and survival. Activated PI3K/AKT (protein kinases B)/mTOR (mammalian target of rapamycin) signaling has been identified in MM primary patient samples and cell lines. In this study, the efficacy of PI3K and mTOR inhibitors in various MM cell lines representing three different prognostic subtypes was tested. Whereas MM cell lines were rather resistant to PI3K inhibition, treatment with the mTOR inhibitor temsirolimus decreases the phosphorylation of key molecules in the PI3K pathway in MM cell lines, leading to G0/G1 cell cycle arrest and thus reduced proliferation. Strikingly, the efficacy of temsirolimus was amplified by combining the treatment with the Mitogen-activated protein kinase kinase (MEK) inhibitor trametinib. Our findings provide a scientific rationale for the simultaneous inhibition of mTOR and MEK as a novel strategy for the treatment of MM.

• Keywords
• MEK, mTOR, multiple myeloma, targeted therapy, temsirolimus, trametinib,
• Publication type
• Journal Article MeSH

Diffuse large B-cell lymphoma (DLBCL) is an aggressive disease that exhibits constitutive activation of phosphoinositide 3-kinase (PI3K) driven by chronic B-cell receptor signaling or PTEN deficiency. Since pan-PI3K inhibitors cause severe side effects, we investigated the anti-lymphoma efficacy of the specific PI3Kβ/δ inhibitor AZD8186. We identified a subset of DLBCL models within activated B-cell-like (ABC) and germinal center B-cell-like (GCB) DLBCL that were sensitive to AZD8186 treatment. On the molecular level, PI3Kβ/δ inhibition decreased the pro-survival NF-κB and AP-1 activity or led to downregulation of the oncogenic transcription factor MYC. In AZD8186-resistant models, we detected a feedback activation of the PI3K/AKT/mTOR pathway following PI3Kβ/δ inhibition, which limited AZD8186 efficacy. The combined treatment with AZD8186 and the mTOR inhibitor AZD2014 overcame resistance to PI3Kβ/δ inhibition and completely prevented outgrowth of lymphoma cells in vivo in cell line- and patient-derived xenograft mouse models. Collectively, our study reveals that subsets of DLBCLs are addicted to PI3Kβ/δ signaling and thus identifies a previously unappreciated role of the PI3Kβ isoform in DLBCL survival. Furthermore, our data demonstrate that combined targeting of PI3Kβ/δ and mTOR is effective in all major DLBCL subtypes supporting the evaluation of this strategy in a clinical trial setting.

• MeSH
• Lymphoma, Large B-Cell, Diffuse * pathology   MeSH
• Phosphatidylinositol 3-Kinases * metabolism   MeSH
• Humans MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Signal Transduction MeSH
• TOR Serine-Threonine Kinases metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• AZD8186 MeSH Browser
• Phosphatidylinositol 3-Kinases * MeSH
• MTOR protein, human MeSH Browser
• TOR Serine-Threonine Kinases MeSH

PURPOSE: PI3K signaling is a common feature of B-cell neoplasms, including chronic lymphocytic leukemia (CLL) and diffuse large B-cell lymphoma (DLBCL), and PI3K inhibitors have been introduced into the clinic. However, there remains a clear need to develop new strategies to target PI3K signaling. PI3K activity is countered by Src homology domain 2-containing inositol-5'-phosphatase 1 (SHIP1) and, here, we have characterized the activity of a novel SHIP1 activator, AQX-435, in preclinical models of B-cell malignancies. EXPERIMENTAL DESIGN: In vitro activity of AQX-435 was evaluated using primary CLL cells and DLBCL-derived cell lines. In vivo activity of AQX-435, alone or in combination with the Bruton's tyrosine kinase (BTK) inhibitor ibrutinib, was assessed using DLBCL cell line and patient-derived xenograft models. RESULTS: Pharmacologic activation of SHIP1 using AQX-435 was sufficient to inhibit anti-IgM-induced PI3K-mediated signaling, including induction of AKT phosphorylation and MYC expression, without effects on upstream SYK phosphorylation. AQX-435 also cooperated with the BTK inhibitor ibrutinib to enhance inhibition of anti-IgM-induced AKT phosphorylation. AQX-435 induced caspase-dependent apoptosis of CLL cells preferentially as compared with normal B cells, and overcame in vitro survival-promoting effects of microenvironmental stimuli. Finally, AQX-435 reduced AKT phosphorylation and growth of DLBCL in vivo and cooperated with ibrutinib for tumor growth inhibition. CONCLUSIONS: Our results using AQX-435 demonstrate that SHIP1 activation may be an effective novel therapeutic strategy for treatment of B-cell neoplasms, alone or in combination with ibrutinib.

• MeSH
• Enzyme Activators pharmacology   MeSH
• Apoptosis drug effects   MeSH
• Leukemia, Lymphocytic, Chronic, B-Cell drug therapy   metabolism   pathology   MeSH
• Lymphoma, Large B-Cell, Diffuse drug therapy   metabolism   pathology   MeSH
• Phosphatidylinositol 3-Kinases chemistry   metabolism   MeSH
• Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases genetics   metabolism   MeSH
• Humans MeSH
• Mice, Inbred NOD MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Antineoplastic Agents pharmacology   MeSH
• Sesquiterpenes pharmacology   MeSH
• Signal Transduction MeSH
• Xenograft Model Antitumor Assays MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Enzyme Activators MeSH
• Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases MeSH
• INPP5D protein, human MeSH Browser
• Antineoplastic Agents MeSH
• Sesquiterpenes MeSH