In laboratory studies, the researchers isolated a protein, caveolin-1, showing that in breast cancer cells this protein can enhance cell death in response to the use of Taxol, one of two taxane chemotherapy drugs used to treat advanced breast and ovarian cancer. But in order to work, they found the protein needs to be "switched on," or phosphorylated. The results were reported in the current (February 23) issue of the Journal of Biological Chemistry.
Their finding suggests it may eventually be possible to test individual breast cancer patients for the status of such molecular markers as caveolin-1 in their tumors to determine the efficacy-to-toxicity ratio for Taxol, said the study’s first author, postdoctoral fellow Ayesha Shajahan, Ph.D., of Lombardi Comprehensive Cancer Center at Georgetown.
"Because breast tumors are not all the same, it is important to know the cancer’s molecular makeup in order to increase the efficiency, and lower the toxicity, of chemotherapy drugs, and this work takes us some steps forward in this goal," she said. "It also offers insights into why some breast cancer cells can become resistant to therapeutic drugs."
Additionally, the study identifies caveolin-1 as a new molecular target for increasing the efficacy of taxanes, according to the study’s lead investigator, Robert Clarke, Ph.D., D.Sc., a Professor of Oncology and Physiology & Biophysics. "This is important because the taxanes are active drugs in breast cancer, so now that we know caveolin-1 is a new mechanism to explain how these drugs kill breast cancer cells, we can potentially take advantage of that fact to improve these agents."
The taxanes are Taxol (also known as paclitaxel) and Taxotere (docetaxel). Taxol was originally derived from the Pacific yew tree, and Taxotere is a semi-synthetic version of Taxol with slight chemical changes. These drugs stabilize a cell’s "microtubules," the road-like protein structures that send chemical signals to all parts of the cell, and which must be flexible if a cell is to divide. Taxanes lock these structures into place, not allowing them to change when the cell begins to divide - which is necessary for tumor growth. Research has also indicated that the drugs induce programmed cell death (apoptosis) in cancer cells by inactivating an "apoptosis stopping protein" called BCL2, thus stopping it from inhibiting cell death.
Caveolin-1 is a protein that is found in most cells under normal conditions and it is involved in an array of cellular events that ranges from vesicle trafficking to cell migration. It is, therefore, as a key regulator of multiple events within the cell.
In cancer, the expression level of caveolin-1 can vary depending on cell type. However, the precise role of caveolin-1 in cancer has been controversial: whether it acts as a suppressor or facilitator of tumor formation depends on the cell type. In human breast cancer, caveolin-1 has been known to act as a tumor suppressor since caveolin-1 expression is down-regulated during the primary stages of breast cancer. More recent studies indicate that that caveolin-1 expression is increased in more aggressive types of breast cancer.
Under the mentorship of Clarke, Shajahan sought to determine factors that regulate expression and function of caveolin-1 in the breast. In this study, the researchers show that in their breast cancer cell model that phosphorylated caveolin-1 increased cell death by activating other key regulators vital to both breast cancer progression and cell death, including BCL2, the same protein that Taxol works on; p21, which controls cell cycle progression; and the tumor suppressor p53.
If caveolin-1 isn’t phosphorylated, breast cancer cells appear to be resistant to Taxol treatment, the researchers conclude. "Thus, this study opens an area of investigation in our lab that will concentrate on understanding how this multi-tasking protein can serve as a marker for chemotherapeutic drug efficacy," Shajahan said.
Laura Cavender | EurekAlert!
Fine organic particles in the atmosphere are more often solid glass beads than liquid oil droplets
21.04.2017 | Max-Planck-Institut für Chemie
Study overturns seminal research about the developing nervous system
21.04.2017 | University of California - Los Angeles Health Sciences
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy