Targeting a lineage-specific PI3KÉ£-Akt signaling module in acute myeloid leukemia using a heterobifunctional degrader molecule.

Dose-limiting toxicity poses a major limitation to the clinical utility of targeted cancer therapies, often arising from target engagement in nonmalignant tissues. This obstacle can be minimized by targeting cancer dependencies driven by proteins with tissue-restricted and/or tumor-restricted expression. In line with another recent report, we show here that, in acute myeloid leukemia (AML), suppression of the myeloid-restricted PIK3CG/p110γ-PIK3R5/p101 axis inhibits protein kinase B/Akt signaling and compromises AML cell fitness. Furthermore, silencing the genes encoding PIK3CG/p110γ or PIK3R5/p101 sensitizes AML cells to established AML therapies. Importantly, we find that existing small-molecule inhibitors against PIK3CG are insufficient to achieve a sustained long-term antileukemic effect. To address this concern, we developed a proteolysis-targeting chimera (PROTAC) heterobifunctional molecule that specifically degrades PIK3CG and potently suppresses AML progression alone and in combination with venetoclax in human AML cell lines, primary samples from patients with AML and syngeneic mouse models.

A versatile method for the identification of senolytic compounds.

The increased burden of senescent cells is as a well-established hallmark of aging and age-related diseases. This finding sparked significant interest in the identification of molecules capable of selectively eliminating senescent cells, so-called senolytics. Here, we fine-tuned a method for the identification of senolytics that is compatible with high-content fluorescence microscopy. We used spectral detector imaging to measure the emission spectrum of unlabeled control or senescent cells. We observed that senescent cells exhibited higher levels of autofluorescence than their non-senescent counterparts, particularly in the cytoplasmic region. Building on this result, we devised a senolytic assay based on co-culturing quiescent and senescent cells, fluorescently tagged in the nuclear region through the overexpression of H2B-GFP and H2B-RFP, respectively. We validated this approach by showing that first generation senolytics were effective in reducing the number of RFP+ nuclei leaving the count of GFP+ nuclei unaffected. The result was confirmed by flow cytometry analysis of nuclei isolated from these quiescent-senescent cell co-cultures. We found that this system enables to capture cell type-specific effects of senolytics as in the case of fisetin, which kills senescent Mouse Embryonic Fibroblasts but not senescent human melanoma SK-MEL-103 cells. This approach is amenable to genetic and chemical screening for the discovery of senolytic compounds in that it overcomes the limitations of current methods, which rely upon costly chemical reagents or fluorescence microscopy using cells labeled with fluorescent cytoplasmic probes that overlap with the autofluorescence signal emitted by senescent cells.

Cooperative regulation of coupled oncoprotein synthesis and stability in triple-negative breast cancer by EGFR and CDK12/13.

Evidence has long suggested that epidermal growth factor receptor (EGFR) may play a prominent role in triple-negative breast cancer (TNBC) pathogenesis, but clinical trials of EGFR inhibitors have yielded disappointing results. Using a candidate drug screen, we identified that inhibition of cyclin-dependent kinases 12 and 13 (CDK12/13) dramatically sensitizes diverse models of TNBC to EGFR blockade. This combination therapy drives cell death through the 4E-BP1-dependent suppression of the translation and translation-linked turnover of driver oncoproteins, including MYC. A genome-wide CRISPR/Cas9 screen identified the CCR4-NOT complex as a major determinant of sensitivity to the combination therapy whose loss renders 4E-BP1 unresponsive to drug-induced dephosphorylation, thereby rescuing MYC translational suppression and promoting MYC stability. The central roles of CCR4-NOT and 4E-BP1 in response to the combination therapy were further underscored by the observation of CNOT1 loss and rescue of 4E-BP1 phosphorylation in TNBC cells that naturally evolved therapy resistance. Thus, pharmacological inhibition of CDK12/13 reveals a long-proposed EGFR dependence in TNBC that functions through the cooperative regulation of translation-coupled oncoprotein stability.

CBF-Beta Mitigates PI3K-Alpha-Specific Inhibitor Killing through PIM1 in PIK3CA-Mutant Gastric Cancer.

PIK3CA is the second most mutated gene in cancer leading to aberrant PI3K/AKT/mTOR signaling and increased translation, proliferation, and survival. Some 4%-25% of gastric cancers display activating PIK3CA mutations, including 80% of Epstein-Barr virus-associated GCs. Small molecules, including pan-PI3K and dual PI3K/mTOR inhibitors, have shown moderate success clinically, due to broad on-target/off-tissue effects. Thus, isoform-specific and mutant selective inhibitors have been of significant interest. However, drug resistance is a problem and has affected success of new drugs. There has been a concerted effort to define mechanisms of resistance and identify potent combinations in many tumor types, though gastric cancer is comparatively understudied. In this study, we identified modulators of the response to the PI3Kα-specific inhibitor, BYL719, in PIK3CA-mutant GCs. We found that loss of NEDD9 or inhibition of BCL-XL conferred hypersensitivity to BYL719, through increased cell-cycle arrest and cell death, respectively. In addition, we discovered that loss of CBFB conferred resistance to BYL719. CBFB loss led to upregulation of the protein kinase PIM1, which can phosphorylate and activate several overlapping downstream substrates as AKT thereby maintaining pathway activity in the presence of PI3Kα inhibition. The addition of a pan-PIM inhibitor re-sensitized resistant cells to BYL719. Our data provide clear mechanistic insights into PI3Kα inhibitor response in PIK3CA-mutant gastric tumors and can inform future work as mutant-selective inhibitors are in development for diverse tumor types. IMPLICATIONS: Loss of either NEDD9 or BCL-XL confers hypersensitivity to PI3K-alpha inhibition whereas loss of CBFB confers resistance through a CBFB/PIM1 signaling axis.

P2RY2-AKT activation is a therapeutically actionable consequence of XPO1 inhibition in acute myeloid leukemia.

Selinexor is a first-in-class inhibitor of the nuclear exportin XPO1 that was recently approved by the US Food and Drug Administration for the treatment of multiple myeloma and diffuse large B-cell lymphoma. In relapsed/refractory acute myeloid leukemia (AML), selinexor has shown promising activity, suggesting that selinexor-based combination therapies may have clinical potential. Here, motivated by the hypothesis that selinexor's nuclear sequestration of diverse substrates imposes pleiotropic fitness effects on AML cells, we systematically catalog the pro- and anti-fitness consequences of selinexor treatment. We discover that selinexor activates PI3Kγ-dependent AKT signaling in AML by upregulating the purinergic receptor P2RY2. Inhibiting this axis potentiates the anti-leukemic effects of selinexor in AML cell lines, patient-derived primary cultures and multiple mouse models of AML. In a syngeneic, MLL-AF9-driven mouse model of AML, treatment with selinexor and ipatasertib outperforms both standard-of-care chemotherapy and chemotherapy with selinexor. Together, these findings establish drug-induced P2RY2-AKT signaling as an actionable consequence of XPO1 inhibition in AML.

Small-molecule targeted therapies induce dependence on DNA double-strand break repair in residual tumor cells.

Residual cancer cells that survive drug treatments with targeted therapies act as a reservoir from which eventual resistant disease emerges. Although there is great interest in therapeutically targeting residual cells, efforts are hampered by our limited knowledge of the vulnerabilities existing in this cell state. Here, we report that diverse oncogene-targeted therapies, including inhibitors of epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), KRAS, and BRAF, induce DNA double-strand breaks and, consequently, ataxia-telangiectasia mutated (ATM)-dependent DNA repair in oncogene-matched residual tumor cells. This DNA damage response, observed in cell lines, mouse xenograft models, and human patients, is driven by a pathway involving the activation of caspases 3 and 7 and the downstream caspase-activated deoxyribonuclease (CAD). CAD is, in turn, activated through caspase-mediated degradation of its endogenous inhibitor, ICAD. In models of EGFR mutant non-small cell lung cancer (NSCLC), tumor cells that survive treatment with small-molecule EGFR-targeted therapies are thus synthetically dependent on ATM, and combined treatment with an ATM kinase inhibitor eradicates these cells in vivo. This led to more penetrant and durable responses in EGFR mutant NSCLC mouse xenograft models, including those derived from both established cell lines and patient tumors. Last, we found that rare patients with EGFR mutant NSCLC harboring co-occurring, loss-of-function mutations in ATM exhibit extended progression-free survival on first generation EGFR inhibitor therapy relative to patients with EGFR mutant NSCLC lacking deleterious ATM mutations. Together, these findings establish a rationale for the mechanism-based integration of ATM inhibitors alongside existing targeted therapies.

Pharmacogenomics in Asia: a systematic review on current trends and novel discoveries.

While early pharmacogenomic studies have primarily been carried out in Western populations, there has been a notable increase in the number of Asian studies over the past decade. We systematically reviewed all pharmacogenomic studies conducted in Asia published before 2016 to highlight trends and identify research gaps in Asia. We observed that pharmacogenomic research in Asia was dominated by larger developed countries, notably Japan and Korea, and mainly driven by local researchers. Studies were focused on drugs acting on the CNS, chemotherapeutics and anticoagulants. Significantly, several novel pharmacogenomic associations have emerged from Asian studies. These developments are highly encouraging for the strength of regional scientific and clinical community and propound the importance of discovery studies in different populations.

Procedural training opportunities for basic pediatric trainees during a 6-month rotation in a level III perinatal centre in Australia.

OBJECTIVE: We aimed to evaluate the procedural training opportunities for basic paediatric trainees in a large tertiary perinatal centre in Australia, to facilitate a realistic expectation of the procedural skills acquired during a 6-month training period. METHODS: A prospective study in which all neonatal registrars and fellows anonymously documented their opportunities for procedural practice (including IV cannulation, intubation, umbilical lines insertion etc) for each shift during a calender month. Based on the averaged number of each shift type worked in a 6-month rotation, the total exposure to each procedure for one 6-month rotation was calculated. RESULTS: During a 6-month period, the registrars had the largest number of exposures on IV cannulation (140.54), venous blood sampling (26.78), bag and mask ventilation (17.38), intubation (7.1) and lumbar puncture (6.68). For the fellows, the largest number of exposure was IV cannulation (127.92) followed by intubation (16.53) then venous blood sampling (21.02). Procedural skills to which registrars had little exposure included chest drains, chest compressions, peripherally inserted central vascular lines and placement of oro-gastric tubes. CONCLUSION: There are ample training opportunities for registrars during a 6-month period. Simulation/animal models for rare procedures will be helpful to increase the trainee's procedural competency.

Dry lung syndrome: a distinct clinical entity.

Infants with preterm prolonged rupture of membranes can present with immediate onset of pulmonary insufficiency and need aggressive ventilatory support. Dry lung syndrome remains an under-recognised clinical entity and very few cases are reported in the literature, though a working definition has been previously proposed. The proposed underlying etiopathogenesis for this is functional hypoplasia of the lung where higher than usual ventilatory pressure for initial 1-2 days can improve oxygenation. This study presents two cases which had similar antenatal and immediate postnatal course, but had diametrically opposite outcomes. Strategies to optimise outcomes in the setting of early premature rupture of the membranes should include antenatal assessment of mothers with monitoring of the liquor volume as well as the strength of foetal breathing movements, in-utero transfer with delivery in perinatal centres and attendance by neonatal staff of appropriate experience.