A new method that determines cell behavior in cancerous cells challenges the notion that targeted therapy simply kills these cells.
Investigators at the Vanderbilt-Ingram Cancer Center (TN, USA), led by Darren Tyson, Research Assistant Professor of Cancer Biology, have developed a new method that could potentially allow for the introduction of personalized clinical trials for cancer therapy.
The new tool, the details of which are published in Nature Methods, may offer ways to improve personalized cancer therapy by predicting tumor response and testing combinations of targeted therapies in an individual patient‘s tumor. The investigators combined powerful automated, time-lapse microscopy with analytical tools and software that they developed in order to observe cell behavior. The research has revealed clues about how cancer cells respond to therapy.
The view to date has been that targeted therapies kill all of the cells harboring a particular mutation; however, until now, no current tests have been able to provide an accurate, detailed picture of the cell behavior that is needed to understand tumor response to drugs.
Erlotinib is a targeted therapy that acts on a growth factor receptor mutated in some lung, brain and other cancers. Using these techniques, the investigators of the present study could capture the behavior of lung cancer cells every 6–10 min for up to 10 days. The approach showed that erlotinib does not simply kill tumor cells, as was previously assumed; the drug also causes some tumor cells to go into a nondividing (quiescent) state or to slow down their rate of division. The authors observed that the drug even affected genetically identical cells (i.e., cells that arose from the same parental cell) differently. The authors suggest that this variability in cell response to the drug may be involved in cancer recurrence and drug resistance.
“These cells are clearly genetically identical – as identical as they can possibly be – because one cell just divided into two, but you get completely different responses: one dies and the other one does not,” explained Tyson. “This suggests that there are other things besides genetics that have to be taken into account.”
In the personalized approach to cancer treatment, a patient‘s tumor is analyzed for a set of mutations to which there are matching drugs that act on those mutations. This approach has worked rather well for many cancers that carry specific mutations, said Vito Quaranta (Vanderbilt-Ingram Cancer Center). The investigators are conducting follow-up experiments to determine what those other factors are and what might underlie this differential response. Looking ahead, the investigators hope to take the technology into small clinical trials to test whether it can predict a patient‘s response to therapy. “We can take samples from the tumor, subject them to this assay and since we are looking at response over time, we will have a rate of response,” Quaranta explained.
Information derived from such assays could include how long a patient‘s tumor will respond to a given therapy before it recurs and could also help determine which patients will require more aggressive treatment. Quaranta believes that the assay will also be able to test combinations of drugs on a patient‘s tumor cells to find the right combination to induce a response. “We are hoping that this assay – or some implementation of this assay – will eventually work like a personalized clinical trial,” stated Quaranta.
As we move ahead to personalize cancer treatment, further knowledge is needed to fill in the gaps regarding cell behavior in the response to current cancer drug treatments.
– Written by Hardaman Baryan
Source: Tyson DR, Garbett SP, Frick PL, Quaranta V. Fractional proliferation: a method to deconvolve cell population dynamics from single-cell data. Nat. Methods 9(9), 923–928 (2012).
Scientists from the Department of Microsystems Engineering (IMTEK) at the University of Freiburg (Freiburg, Germany) have developed a method for performing highly parallel PCR reactions in a picowell array (PWA). The PWA can copy 100,000 different DNA sequences simultaneously, and has the potential to provide further insights into the regulatory systems of an organism. This knowledge in the context of personalized medicine can help to develop a tailored therapy for a specific patient group and holds promise to advance the field further.
The research group included Jochen Hoffmann, Guenther Roth and Roland Zengerle. The project was supported by the ‘Program for Excellency in Science and Technology‘ as part of a grant from the Hans L Merkle-Stiftung, Germany.
The PWA is a chip with 100,000 wells in which the DNA sequences are placed to achieve a statistical distribution of one sequence per well, with a microscopic slide placed above all the wells. The DNA sequences are replicated by the PCR technique, and the resultant DNA copies bind to the microscopic slide at exactly the position of the original DNA sequence. Next-generation sequencing systems decode the DNA copies in the wells of the array. The microscopic slides are likened to DNA microarrays, as they can be used for the rapid and cost-effective analysis of entire genomes. The advantage of the method is that there is no need for other equipment or additional transfer steps.
The topic is being further developed by the ‘Lab-on-a-Chip‘ research groups based on the campus of the Faculty for Engineering in cooperation with the Laboratory for MEMS Applications (Freiburg, Germany) and the Institut für Mikro- und Informationstechnik der Hahn-Schickard-Gesellschaft (Villingen-Schwenningen, Germany).
The PWA can be used for the genome analysis of a tumor cell and could reveal which of its signal paths are defective. Future avenues of research can be identified which have the capability for developing targeted therapies for an array of diseases.
– Written by Hardaman Baryan
Source: Hoffmann J, Trotter M, von Stetten F, Zengerle R, Roth G. Solid-phase PCR in a picowell array for immobilizing and arraying 100 000 PCR products to a microscope slide. Lab Chip 12(17), 3049–3054 (2012).
Quintiles Global Laboratories (NC, USA), a leading biopharmaceutical company supporting worldwide trials, has increased its ability to optimize drug development by acquiring a leading provider of genomics drug testing and analysis services, Expression Analysis, Inc. (NC, USA).
Expression Analysis is a leading provider of analysis services such as whole-genome and genotyping assays, next-generation sequencing services, sequence enrichment technologies and bioinformatics support, which can be used across multiple platforms.
Quintiles are now able to provide these services to their biopharma, academic, government and nonprofit customers. This is the latest acquisition by the company in their bid to help their customers use genomics to further increase the understanding of many diseases, develop genetic tools and deliver safer and more effective therapies based on the genetic make-up of the disease and the patient.
Speaking about the acquisition in the company press release, Senior Vice President of Quintiles, Thomas Wollman, said that: “The addition of Expression Analysis‘s Genomic Know-How® to Quintiles is another step forward in our efforts to bring personalized medicine into mainstream drug development. Its expertise in genetic sequencing and advanced bioinformatics is essential to understanding diseases and drugs at the molecular level.” Expression Analysis are also positive about the deal, the terms of which have not been disclosed. Steve McPhail, Expression Analysis President and Chief Executive Officer, said: “The combination of Quintiles Global Laboratories and Expression Analysis genomic technology excellence will facilitate worldwide access to resources and expertise to drive improvements in the diagnosis, treatment and management of complex disease.”
– Written by Claire Attwood
Source: Quintiles Newsroom Press Release: www.quintiles.com/news/press-releases/2012–8–13/acquires-expression-personalized-medicine
A study published by a group of researchers from the University of Leicester (Leicester, UK), the University of California (CA, USA) and Cancer Research UK (London, UK) in the journal Genes and Development puts forth the case for genetically screening individuals prior to the treatment of melanoma skin cancer.
The lead author Catrin Pritchard discussed the findings that certain genetic mutations in the tumors of patients with melanoma skin cancer may influence how they respond to the drug vemurafenib; and may also explain why some patients develop secondary nonmelanoma skin cancers.
Vemurafenib targets a common defect, called V600E, in the gene BRAF, that works by inhibiting BRAF from activating a key pathway known to stimulate cancer growth. Interestingly, the defect is not present in all individuals who develop melanoma, but in approximately half of the melanomas. Furthermore, 18% of patients treated with vemurafenib go on to develop squamous cell carcinoma, a less serious form of nonmelanoma skin cancer that requires surgical removal.
To discover why such differences occur, a group of rare inherited development disorders known as ‘RASopathies‘, which are also caused by defects in BRAF, were studied in mice. A rare defect in BRAF, known as L597V, found in melanoma patients and people with RASopathies, was specifically investigated. On its own, L597V was not found to cause cancer, but when a second gene, RAS, was identified as defective too, the mice developed cancers similar to those caused by the common defect V600E. It was also noted that the tumors that occurred were comparable, but the biology behind the cancer was different.
Pritchard explained: “This study shows that the L597V fault only leads to cancer when it happens alongside other faults in the cell, explaining why people with RASopathies do not usually develop the disease. But because this rare fault works in a different way from the common one, vemurafenib has the opposite effect and actually causes secondary tumors, albeit less serious nonmelanoma ones. This suggests that people should be screened to see what faults they have before they are given vemurafenib.”
The study potentially highlights that the drug may enhance cancer growth in patients with the rare defect in BRAF, based on the reverse effect seen on these cells in the laboratory. However, Julie Sharp (Cancer Research UK) stated that: “We now need clinical trials to see whether analyzing BRAF faults can help predict response to vemurafenib in people, as well as mice.”
– Written by Hardaman Baryan
Sources: Andreadi C, Cheung LK, Giblett S et al. The intermediate-activity L597V BRAF mutant acts as an epistatic modifier of oncogenic RAS by enhancing signalling through the RAF/MEK/ERK pathway. Genes Dev. 26(17), 1945–1958 (2012); Press Release: Cancer Research UK: http://info.cancerresearchuk.org/news/archive/pressrelease/2012–08–13-screening-before-vemurafenib