Synthetic Lethal Targeting of ARID1A-Mutant Ovarian Clear Cell Tumors with Dasatinib

New targeted approaches to ovarian clear cell carcinomas (OCCC) are needed, given the limited treatment options in this disease and the poor response to standard chemotherapy. Using a series of high-throughput cell-based drug screens in OCCC tumor cell models, we have identified a synthetic lethal (SL) interaction between the kinase inhibitor dasatinib and a key driver in OCCC, ARID1A mutation. Imposing ARID1A deficiency upon a variety of human or mouse cells induced dasatinib sensitivity, both in vitro and in vivo, suggesting that this is a robust synthetic lethal interaction. The sensitivity of ARID1A-deficient cells to dasatinib was associated with G1-S cell-cycle arrest and was dependent upon both p21 and Rb. Using focused siRNA screens and kinase profiling, we showed that ARID1A-mutant OCCC tumor cells are addicted to the dasatinib target YES1. This suggests that dasatinib merits investigation for the treatment of patients with ARID1A-mutant OCCC. Mol Cancer Ther; 15(7); 1472-84. ©2016 AACR.

Dsh homolog DVL3 mediates resistance to IGFIR inhibition by regulating IGF-RAS signaling

Drugs that inhibit insulin-like growth factor 1 (IGFI) receptor IGFIR were encouraging in early trials, but predictive biomarkers were lacking and the drugs provided insufficient benefit in unselected patients. In this study, we used genetic screening and downstream validation to identify the WNT pathway element DVL3 as a mediator of resistance to IGFIR inhibition. Sensitivity to IGFIR inhibition was enhanced specifically in vitro and in vivo by genetic or pharmacologic blockade of DVL3. In breast and prostate cancer cells, sensitization tracked with enhanced MEK-ERK activation and relied upon MEK activity and DVL3 expression. Mechanistic investigations showed that DVL3 is present in an adaptor complex that links IGFIR to RAS, which includes Shc, growth factor receptor-bound-2 (Grb2), son-of-sevenless (SOS), and the tumor suppressor DAB2. Dual DVL and DAB2 blockade synergized in activating ERKs and sensitizing cells to IGFIR inhibition, suggesting a nonredundant role for DVL3 in the Shc-Grb2-SOS complex. Clinically, tumors that responded to IGFIR inhibition contained relatively lower levels of DVL3 protein than resistant tumors, and DVL3 levels in tumors correlated inversely with progression-free survival in patients treated with IGFIR antibodies. Because IGFIR does not contain activating mutations analogous to EGFR variants associated with response to EGFR inhibitors, we suggest that IGF signaling achieves an equivalent integration at the postreceptor level through adaptor protein complexes, influencing cellular dependence on the IGF axis and identifying a patient population with potential to benefit from IGFIR inhibition.

Synthetic lethality of PARP and NAMPT inhibition in triple-negative breast cancer cells

PARP inhibitors have been proposed as a potential targeted therapy for patients with triple-negative (ER-, PR-, HER2-negative) breast cancers. However, it is as yet unclear as to whether single agent or combination therapy using PARP inhibitors would be most beneficial. To better understand the mechanisms that determine the response to PARP inhibitors, we investigated whether enzymes involved in metabolism of the PARP substrate, β-NAD(+) , might alter the response to a clinical PARP inhibitor. Using an olaparib sensitization screen in a triple-negative (TN) breast cancer model, we identified nicotinamide phosphoribosyltransferase (NAMPT) as a non-redundant modifier of olaparib response. NAMPT is a rate-limiting enzyme involved in the generation of the PARP substrate β-NAD(+) and the suppression of β-NAD(+) levels by NAMPT inhibition most likely explains these observations. Importantly, the combination of a NAMPT small molecule inhibitor, FK866, with olaparib inhibited TN breast tumour growth in vivo to a greater extent than either single agent alone suggesting that assessing NAMPT/PARP inhibitor combinations for the treatment of TN breast cancer may be warranted.

Aetiology of diarrhoea among persons with HIV and their family members in rural Uganda: a community-based study

OBJECTIVES

To identify pathogens associated with diarrhoea in HIV-infected persons and their HIV-uninfected family members.

DESIGN

Prospective cohort study.

SETTING

Rural community in eastern Uganda.

SUBJECTS

Eight hundred and seventy nine HIV-infected adults (74% females and median age 35 years (IQR, 29-41) and 2771 HIV-uninfected family members (51% females and median age 11 years (IQR 6-16) were included.

MAIN OUTCOME MEASURES

Using microscopy and culture, stools were tested for parasites, bacteria and bacterial-antimicrobial-susceptibility. Logistic regression models, adjusting for age, CD4 cells, season, household clustering and use of safe-water system were used for relationships between pathogens, diarrhoea and HIV.

RESULTS

Persons with HIV had similar pathogens in diarrhoeal (69%) and nondiarrhoeal stools (57%). Most diarrhoea was not associated with identifiable aetiology; the population attributable risk of diarrhoea for known diarrhoea pathogens was 32%. Enteric bacteria (19%), enteropathogenic or enterotoxigenic E. coli (8%), Aeromonas species (7%), Strongyloides stercoralis (8%) and Cryptosporidium parvum (5%). HIV-infected, stools had more Cryptosporidium parvum than HIV-uninfected (OR 2.64, 95% CI 1.43-4.87). Most bacteria were resistant to commonly used antimicrobials irrespective of HIV status.

CONCLUSIONS

Irrespective of HIV-status, aetiologies of majority of their diarrhoea in Uganda cannot be identified by microscopy and culture. Bacterial pathogens isolated have high resistance to common antimicrobials. Empiric treatment should be tailored to local bacterial-resistance patterns.