Common chemotherapy drugs may not work as thought: Study

Chemotherapy may not be reaching its full potential in part because researchers and doctors have long misunderstood how some of the most common cancer drugs actually ward off tumours according to a new studyFor decades researchers have believed that a class of drugs called microtubule poisons treat cancerous tumours by halting mitosis or the division of cellsNow a team of University of WisconsinMadison scientists has found that in patients microtubule poisons dont actually stop cancer cells from dividing Instead these drugs alter mitosis sometimes enough to cause new cancer cells to die and the disease to regressCancers grow and spread because cancerous cells divide and multiply indefinitely unlike normal cells which are limited in the number of times they can split into new cellsThe assumption that microtubule poisons stop cancer cells from dividing is based on lab studies demonstrating just thatPublished in the journal PLOS Biology the study broadens previous findings about a specific microtubule poison called paclitaxelSometimes prescribed under the brand name Taxol paclitaxel is used to treat common malignancies including those originating in the ovaries and lungsFor decades we all thought that the way paclitaxel works in patient tumours is by arresting them in mitosis This is what I was taught as a graduate student We all knew this In cells in a dish labs all over the world have shown this The problem was we were all using it at concentrations higher than those that actually get into the tumour said Beth Weaver a professor in the departments of oncology and cell and regenerative biology about the previous researchWeaver and her team wanted to know if other microtubule poisons work the same way as paclitaxel not by stopping mitosis but by messing it upThe team studied tumour samples taken from breast cancer patients who received standard antimicrotubule chemotherapy They measured how much of the drugs made it into the tumours and studied how the tumour cells responded They found that while the cells continued to divide after being exposed to the drug they did so abnormallyThis abnormal division can lead to tumour cell deathNormally a cells chromosomes are duplicated before the two identical sets migrate to opposite ends of the cell mitosis in a process called chromosomal segregation One set of chromosomes is sorted into each of two new cells This migration occurs because the chromosomes are attached to a cellular machine known as the mitotic spindle Spindles are made from cellular building blocks called microtubules Normal spindles have two ends known as spindle polesWeaver found that paclitaxel and other microtubule poisons cause abnormalities that lead cells to form three four or sometimes five poles during mitosis even as they continue to make just one copy of chromosomesThese poles then attract the two complete sets of chromosomes in more than two directions scrambling the genomeSo after mitosis you have daughter cells that are no longer genetically identical and have lost chromosomes Weaver said We calculated that if a cell loses at least 20 per cent of its DNA content it is very likely going to dieThese findings reveal the likely reason why microtubule poisons are effective for many patients Importantly they also help explain why attempts to find new chemo drugs based solely on stopping mitosis have been so disappointing Weaver saidThis story has been sourced from a third party syndicated feed agencies Midday accepts no responsibility or liability for its dependability trustworthiness reliability and data of the text Midday managementmiddaycom reserves the sole right to alter delete or remove without notice the content in its absolute discretion for any reason whatsoever