Targeting endocrine resistance: is there a role for mTOR inhibition?

The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is a critical intracellular signaling cascade that mediates both growth factor-induced proliferation and cell survival with deregulated signaling through this pathway, a feature of most cancers. Here, we review the role of the PI3K/Akt/mTOR pathway in endocrine-resistant breast cancer and discuss preclinical and clinical studies combining endocrine therapy with mTOR inhibition. Key to the success of such an approach will be a clinical trial design incorporating appropriate tumor selection and validation of biomarkers predicting benefit. Ultimately, a greater understanding of the biology and compensatory mechanisms will allow the partnering of key signal transduction inhibitors together to provide maximal "vertical" or "horizontal" blockade with further preclinical and clinical studies planned to examine possible synergistic combinations with endocrine therapy.

Recurrent high-grade glioma

OPINION STATEMENT

Opinions vary on the best treatment options for recurrent high-grade glioma. Some argue that bevacizumab should become standard of care for patients with recurrent glioblastoma, especially in light of recent FDA approval for this indication. However, this opinion is not uniformly accepted. Age, performance status, histology, tumor size and location, O6-methylguanine-DNA methyltransferase (MGMT) methylation status for glioblastoma, 1p/19q status for oligodendroglial tumors, and the number and types of prior therapies are important considerations. In addition, recurrent disease must be distinguished from "pseudoprogression" due to treatment effects. Enrollment in a clinical trial is the optimal choice for most patients with recurrent high-grade glioma after failure of radiation therapy and temozolomide. For patients who are ineligible or do not have access to clinical trials, then either bevacizumab monotherapy or bevacizumab in combination with a second agent such as irinotecan is recommended. Involved-field external beam radiation should be considered for patients with anaplastic gliomas who have not received radiation. For patients with anaplastic astrocytoma who progress after radiotherapy, temozolomide may be used. For patients with anaplastic oligodendroglioma who progress after radiotherapy, PCV chemotherapy and temozolomide are options. Oligodendroglial tumors with 1p/19q deletions are more likely to respond to treatment. In the past, carmustine was commonly used to treat recurrent high-grade glioma, but the utility of carmustine in the modern era is unknown because most studies were performed prior to the widespread use of temozolomide. High-precision re-irradiation such as stereotactic radiosurgery is another option in high-grade glioma, especially for patients with poor bone marrow reserve or inability to tolerate chemotherapy, but there is a paucity of studies with adequate controls. Surgery may be useful as adjuvant treatment for patients with symptoms due to mass effect or for patients requiring definitive histopathology, but it generally should be combined with another treatment modality. Emerging therapies, including dose-intense temozolomide regimens, targeted molecular inhibitors, other antiangiogenic therapies, viral gene therapies, immunotherapies, and convection-enhanced delivery of targeted immunotoxins, are still under investigation.

Other options in the treatment of advanced breast cancer

Many cytotoxic therapies are available for patients with metastatic breast cancer, but response rates are low and acquired or de novo resistance is virtually universal. Among the agents that are used in the treatment of pretreated metastatic breast cancer are vinorelbine, gemcitabine, nab-paclitaxel, pemetrexed, platinum salts (eg, cisplatin, carboplatin), pegylated liposomal doxorubicin, etoposide, and irinotecan. Therapies that improve overall survival in patients with anthracycline- and taxane-resistant metastatic breast cancer are needed.

Src inhibitors in lung cancer: current status and future directions

Src tyrosine kinases regulate multiple genetic and signaling pathways involved in the proliferation, survival, angiogenesis, invasion, and migration of various types of cancer cells They are frequently expressed and activated in many cancer types, including lung cancer. Several Src inhibitors, including dasatinib, saracatinib, bosutinib, and KX2-391, are currently being investigated in clinical trials. Preliminary results of the use of single-agent Src inhibitors in unselected patients with lung cancer show that these inhibitors have a favorable safety profile and anticancer activity. Their combination with cytotoxic chemotherapy, other targeted therapy, and radiation therapy is currently being explored. In this review, we summarize the rationale for and the current status of Src inhibitor development and discuss future directions based on emerging preclinical data.