Andrea E. Wahner Hendrickson

ATR Inhibition Broadly Sensitizes Ovarian Cancer Cells to Chemotherapy Independent of BRCA Status

Replication stress and DNA damage activate the ATR-Chk1 checkpoint signaling pathway that licenses repair and cell survival processes. In this study, we examined the respective roles of the ATR and Chk1 kinases in ovarian cancer cells using genetic and pharmacologic inhibitors in combination with cisplatin, topotecan, gemcitabine, and the PARP inhibitor veliparib (ABT-888), four agents with clinical activity in ovarian cancer. RNA interference (RNAi)-mediated depletion or inhibition of ATR sensitized ovarian cancer cells to all four agents. In contrast, while cisplatin, topotecan, and gemcitabine each activated Chk1, RNAi-mediated depletion or inhibition of this kinase in cells sensitized them only to gemcitabine. Unexpectedly, we found that neither the ATR kinase inhibitor VE-821 nor the Chk1 inhibitor MK-8776 blocked ATR-mediated Chk1 phosphorylation or autophosphorylation, two commonly used readouts for inhibition of the ATR-Chk1 pathway. Instead, their ability to sensitize cells correlated with enhanced CDC25A levels. In addition, we also found that VE-821 could further sensitize BRCA1-depleted cells to cisplatin, topotecan, and veliparib beyond the potent sensitization already caused by their deficiency in homologous recombination. Taken together, our results established that ATR and Chk1 inhibitors differentially sensitize ovarian cancer cells to commonly used chemotherapy agents and that Chk1 phosphorylation status may not offer a reliable marker for inhibition of the ATR-Chk1 pathway. A key implication of our work is the clinical rationale it provides to evaluate ATR inhibitors in combination with PARP inhibitors in BRCA1/2-deficient cells.

Dual mTORC1/mTORC2 inhibition diminishes Akt activation and induces Puma-dependent apoptosis in lymphoid malignancies.

The mammalian target of rapamycin (mTOR) plays crucial roles in proliferative and antiapoptotic signaling in lymphoid malignancies. Rapamycin analogs, which are allosteric mTOR complex 1 (mTORC1) inhibitors, are active in mantle cell lymphoma and other lymphoid neoplasms, but responses are usually partial and short-lived. In the present study we compared the effects of rapamycin with the dual mTORC1/mTORC2 inhibitor OSI-027 in cell lines and clinical samples representing divers lymphoid malignancies. In contrast to rapamycin, OSI-027 markedly diminished proliferation and induced apoptosis in a variety of lymphoid cell lines and clinical samples, including specimens of B-cell acute lymphocytic leukemia (ALL), mantle cell lymphoma, marginal zone lymphoma and Sezary syndrome. Additional analysis demonstrated that OSI-027-induced apoptosis depended on transcriptional activation of the PUMA and BIM genes. Overexpression of Bcl-2, which neutralizes Puma and Bim, or loss of procaspase 9 diminished OSI-027-induced apoptosis in vitro. Moreover, OSI-027 inhibited phosphorylation of mTORC1 and mTORC2 substrates, up-regulated Puma, and induced regressions in Jeko xenografts. Collectively, these results not only identify a pathway that is critical for the cytotoxicity of dual mTORC1/mTORC2 inhibitors, but also suggest that simultaneously targeting mTORC1 and mTORC2 might be an effective anti-lymphoma strategy in vivo.

Oncologic Emergencies: Pathophysiology, Presentation, Diagnosis, and Treatment

Oncologic emergencies can occur at any time during the course of a malignancy, from the presenting symptom to end‐stage disease. Although some of these conditions are related to cancer therapy, they are by no means confined to the period of initial diagnosis and active treatment. In the setting of recurrent malignancy, these events can occur years after the surveillance of a cancer patient has been appropriately transferred from a medical oncologist to a primary care provider. As such, awareness of a patients cancer history and its possible complications forms an important part of any clinicians knowledge base. Prompt identification of and intervention in these emergencies can prolong survival and improve quality of life, even in the setting of terminal illness. This article reviews hypercalcemia, hyponatremia, hypoglycemia, tumor lysis syndrome, cardiac tamponade, superior vena cava syndrome, neutropenic fever, spinal cord compression, increased intracranial pressure, seizures, hyperviscosity syndrome, leukostasis, and airway obstruction in patients with malignancies. Chemotherapeutic emergencies are also addressed. CA Cancer J Clin 2011.

Expression of Insulin Receptor Isoform A and Insulin-like Growth Factor-1 Receptor in Human Acute Myelogenous Leukemia: Effect of the Dual-Receptor Inhibitor BMS-536924 In vitro

The insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF1R) are receptor tyrosine kinases that participate in mitogenic and antiapoptotic signaling in normal and neoplastic epithelia. In the present study, immunoblotting and reverse transcription-PCR demonstrated expression of IGF1R and IR isoform A in acute myelogenous leukemia (AML) cell lines as well as in >80% of clinical AML isolates. Treatment with insulin enhanced signaling through the Akt and MEK1/2 pathways as well as survival of serum-starved AML cell lines. Conversely, treatment with BMS-536924, a dual IGF1R/IR kinase inhibitor that is undergoing preclinical testing, inhibited constitutive receptor phosphorylation as well as downstream signaling through MEK1/2 and Akt. These changes inhibited proliferation and, in some AML cell lines, induced apoptosis at submicromolar concentrations. Likewise, BMS-536924 inhibited leukemic colony formation in CD34+ clinical AML samples in vitro. Collectively, these results not only indicate that expression of IGF1R and IR isoform A is common in AML but also show that interruption of signaling from these receptors inhibits proliferation in clinical AML isolates. Accordingly, further investigation of IGF1R/IR axis as a potential therapeutic target in AML appears warranted.

Targeting immune checkpoints in unresectable metastatic cutaneous melanoma: a systematic review and meta‐analysis of anti‐CTLA‐4 and anti‐PD‐1 agents trials

Anti‐cytotoxic T lymphocyte‐associated antigen‐4 (CTLA‐4) and anti‐programmed cell death‐1 (PD‐1) inhibitors have been shown to significantly improve survival in patients with metastatic cutaneous melanoma. However, there was some heterogeneity as well as some variation in the degree of benefit across studies. We reviewed randomized trials and performed a meta‐analysis to determine the efficacy and safety of immune checkpoint inhibitors in comparison with conventional regimens. Eligible studies were limited to randomized controlled trials comparing anti‐CTLA‐4 or anti‐PD‐1 inhibitors to chemotherapy or vaccination treatment in adult patients with unresectable cutaneous metastatic melanoma. Progression‐free survival (PFS) rate at 6 months was 28.5% versus 17.7% (RR: 0.84, 95% CI: 0.76–0.93), overall survival (OS) rate at 1 year was 51.2% versus 38.8% (RR: 0.72, 95% CI: 0.59–0.88), and overall response rate (ORR) at 6 months was 29.6% versus 17.7% (RR: 0.85, 95% CI: 0.76–0.95) favoring immune check point inhibitors over chemotherapies or vaccination. Immune check point inhibitors were associated with more frequent immune‐related adverse events at 13.7% versus 2.4% of treated patients (RR: 6.74, 95% CI: 4.65–9.75). Subgroup analyses demonstrated significant PFS (RR: 0.92 vs. 0.74, P < 0.00001) and ORR (RR: 0.95 vs. 0.76, P = 0.0004) improvement with anti‐PD‐1 treatment compared to anti‐CTLA‐4 when each of them was compared to control treatments. Collectively, these results demonstrate that immune checkpoint inhibitors have superior outcomes compared to conventional chemotherapies or vaccination, and support the results of recent randomized trials that showed superior outcomes with anti‐PD‐1 agents over ipilimumab in unresectable metastatic cutaneous melanoma patients.

Anticancer therapy: Boosting the bang of Bim

Even though activating mutations of B-Raf, a kinase atop the MAPK signaling cascade, reportedly sensitize tumor cells to MEK inhibitors, Raf and MEK inhibitors have exhibited limited clinical activity. In this issue of the JCI, Cragg et al. report that MEK inhibition upregulates the proapoptotic Bcl-2 family member Bim but induces little regression of human melanoma xenografts in mice unless the Bcl-2 antagonist ABT-737 is added (see the related article beginning on page 3651). These findings illustrate the potential benefit of simultaneously inhibiting oncogenic kinases and inhibiting Bcl-2 action in solid tumors.

A Phase II Study of Gemcitabine in Combination with Tanespimycin in Advanced Epithelial Ovarian and Primary Peritoneal Carcinoma

OBJECTIVE To evaluate the efficacy and biological effects of the gemcitabine/tanespimycin combination in patients with advanced ovarian and peritoneal cancer. To assess the effect of tanespimycin on tumor cells, levels of the chaperone proteins HSP90 and HSP70 were examined in peripheral blood mononuclear cells (PBMC) and paired tumor biopsy lysates. METHODS Two-cohort phase II clinical trial. Patients were grouped according to prior gemcitabine therapy. All participants received tanespimycin 154 mg/m(2) on days 1 and 9 of cycle 1 and days 2 and 9 of subsequent cycles. Patients also received gemcitabine 750 mg/m(2) on day 8 of the first treatment cycle and days 1 and 8 of subsequent cycles. RESULTS The tanespimycin/gemcitabine combination induced a partial response in 1 gemcitabine naïve patient and no partial responses in gemcitabine resistant patients. Stable disease was seen in 6 patients (2 gemcitabine naïve and 4 gemcitabine resistant). The most common toxicities were hematologic (anemia and neutropenia) as well as nausea and vomiting. Immunoblotting demonstrated limited upregulation of HSP70 but little or no change in levels of most client proteins in PBMC and paired tumor samples. CONCLUSIONS Although well tolerated, the tanespimycin/gemcitabine combination exhibited limited anticancer activity in patients with advanced epithelial ovarian and primary peritoneal carcinoma, perhaps because of failure to significantly downregulate the client proteins at clinically achievable exposures.

4EBP1/c-MYC/PUMA and NF-κB/EGR1/BIM pathways underlie cytotoxicity of mTOR dual inhibitors in malignant lymphoid cells

The mammalian target of rapamycin (mTOR), a kinase that regulates proliferation and apoptosis, has been extensively evaluated as a therapeutic target in multiple malignancies. Rapamycin analogs, which partially inhibit mTOR complex 1 (mTORC1), exhibit immunosuppressive and limited antitumor activity, but sometimes activate survival pathways through feedback mechanisms involving mTORC2. Thus, attention has turned to agents targeting both mTOR complexes by binding the mTOR active site. Here we show that disruption of either mTOR-containing complex is toxic to acute lymphocytic leukemia (ALL) cells and identify 2 previously unrecognized pathways leading to this cell death. Inhibition of mTORC1-mediated 4EBP1 phosphorylation leads to decreased expression of c-MYC and subsequent upregulation of the proapoptotic BCL2 family member PUMA, whereas inhibition of mTORC2 results in nuclear factor-κB-mediated expression of the Early Growth Response 1 (EGR1) gene, which encodes a transcription factor that binds and transactivates the proapoptotic BCL2L11 locus encoding BIM. Importantly, 1 or both pathways contribute to death of malignant lymphoid cells after treatment with dual mTORC1/mTORC2 inhibitors. Collectively, these observations not only provide new insight into the survival roles of mTOR in lymphoid malignancies, but also identify alterations that potentially modulate the action of mTOR dual inhibitors in ALL.

Assessment of published models and prognostic variables in epithelial ovarian cancer at Mayo Clinic

Objectives Epithelial ovarian cancer (EOC) is an aggressive disease in which first line therapy consists of a surgical staging/debulking procedure and platinum based chemotherapy. There is significant interest in clinically applicable, easy to use prognostic tools to estimate risk of recurrence and overall survival. In this study we used a large prospectively collected cohort of women with EOC to validate currently published models and assess prognostic variables. Methods Women with invasive ovarian, peritoneal, or fallopian tube cancer diagnosed between 2000-2011 and prospectively enrolled into the Mayo Clinic Ovarian Cancer registry were identified. Demographics and known prognostic markers as well as epidemiologic exposure variables were abstracted from the medical record and collected via questionnaire. Six previously published models of overall and recurrence-free survival were assessed for external validity. In addition, predictors of outcome were assessed in our dataset. Results Previously published models validated with a range of c-statistics (0.587-0.827), though application of models containing variables not part of routine practice were somewhat limited by missing data; utilization of all applicable models and comparison of results is suggested. Examination of prognostic variables identified only the presence of ascites and ASA score to be independent predictors of prognosis in our dataset, albeit with marginal gain in prognostic information, after accounting for stage and debulking. Conclusions Existing prognostic models for newly diagnosed EOC showed acceptable calibration in our cohort for clinical application. However, modeling of prospective variables in our dataset reiterates that stage and debulking remain the most important predictors of prognosis in this setting.

Insulin Receptor A and IGF-IR in AML –Response

We applaud Chapuis and coworkers for recently showing an autocrine loop involving insulin-like growth factor I (IGF-I) and its receptor (IGF-IR) in acute myelogenous leukemia (AML). Although these studies identify IGF-IR as a potential therapeutic target, they do not address the contribution of