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MDR1/gp170 expression in breast tumors is associated with treatment and with a poor response to chemotherapy. The data are consistent with a contributory role for MDR1/gp170 in the multidrug resistance in some breast tumors.

Resistance to chemotherapy is a critical issue in the management of breast cancer patients. The nature of clinical drug resistance is likely to be multifactorial. However, in the last decade considerable attention has been dedicated to the role played by membrane transporter proteins belonging to the ATP binding cassette protein superfamily, and in particular by the MDR1 product P-glycoprotein (Pgp) and the multidrug resistance protein (MRP1). Heterogeneity of results is a common feature of studies evaluating the expression and prognostic role of these proteins, due to both methodological and biological factors. Nonetheless, Pgp and MRP1 are detected in a significant proportion of untreated breast cancers (on average 40 and 50% respectively, by immunohistochemistry), without a clear and consistent association with cancer stage. Exposure to chemotherapy increases the expression of both proteins. In vitro studies on primary cultures of breast cancer cells obtained at surgery consistently show an association between Pgp (protein) or MDR1 (mRNA) expression and resistance to chemotherapy. However, the correlation with clinical drug resistance is not as well defined. A stronger association of Pgp/MDR1 with response rates has been observed when expression or an increase in expression are detected immediately following chemotherapy. Correlations with prognosis appear more evident in studies using immunohistochemistry, in adjuvant and neoadjuvant settings. Evidence of clinical reversal of drug resistance by verapamil suggests a functional role of Pgp in drug resistance, although the significance of the evidence is generally weakened by poor trial designs. Future studies should take into account the multifactorial nature of drug resistance in breast cancer and use standardized approaches with adequate controls. Expression studies should be complemented by well-designed trials of drug-resistance reversal using target-specific chemosensitizing agents, and relating the results to the levels of expression of the target proteins.

During the conflicts of the Global War on Terror, which are Operation Enduring Freedom (OEF) in Afghanistan and Operation Iraqi Freedom (OIF), there have been over a quarter of a million diagnosed cases of traumatic brain injury (TBI). The vast majority are due to explosive blast. Although explosive blast TBI (bTBI) shares many clinical features with closed head TBI (cTBI) and penetrating TBI (pTBI), it has unique features, such as early cerebral edema and prolonged cerebral vasospasm. Evolving work suggests that diffuse axonal injury (DAI) seen following explosive blast exposure is different than DAI from focal impact injury. These unique features support the notion that bTBI is a separate and distinct form of TBI. This review summarizes the current state of knowledge pertaining to bTBI. Areas of discussion are: the physics of explosive blast generation, blast wave interaction with the bony calvarium and brain tissue, gross tissue pathophysiology, regional brain injury, and cellular and molecular mechanisms of explosive blast neurotrauma.

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