Currently, a lack of microarray screening technology is hampering its successful integration into routine clinical care. However, a team of scientists from the US Department of Energy‘s Lawrence Berkeley National Laboratory (Berkeley Lab; CA, USA) have invented a new technique that may help to solve this problem. In their study, which was recently published in Nature Biotechnology, they describe a method for the sensitive and label-free electrostatic readout of DNA or RNA hybridization on microarrays. Their technique, which is based on the principle of electrostatic repulsion, is relatively simple and inexpensive to implement and can be carried out in just a few minutes.
“One of the most amazing things about our electrostatic detection method is that it requires nothing more than the naked eye to read out results that currently require chemical labeling and confocal laser scanners”, enthused the lead researcher, Jay Groves, a chemist with joint appointments at Berkeley Lab‘s Physical Biosciences Division and the Chemistry Department of the University of California at Berkeley. “We believe this technique could revolutionize the use of DNA microarrays for both research and diagnostics”.
In their paper, Groves and colleagues describe the method, which involves dispersing a fluid containing thousands of electrically charged microscopic beads or spheres made of silica across the surface of a DNA microarray and then observing the Brownian motion of the spheres. This provides measurements of the electrical charges of the DNA molecules. These measurements can, in turn, be used to interrogate millions of DNA sequences at a time. The authors suggest that since the naked eye is sufficient to read out the hybridization, their approach may facilitate the broad application of multiplexed assays.
“Since the resolution of electrostatic-based imaging is determined by the number of particle observations rather than by the diffraction limit of light, our readouts could serve as a form of ultramicroscopy”, explains Grove.
The authors conclude that, “The real grand challenge for this technology, however, will be for us to find suitable industrial partners with whom we can work to see that useful new products actually make it to market”.
Source: Clack NG, Salaita K, Groves JT: Electrostatic readout of DNA microarrays with charged microspheres. Nat. Biotechnol. 26(7), 825–830 (2008).
EMEA Approval of Pegasys®: A New Treatment that Individualizes Therapy for a Subgroup of Hepatitis C Patients
On 26 June 2008, the European Medicines Agency (EMEA) approved a 16-week course of treatment for certain hepatitis C patients that included therapy with Pegasys® (peginterferon α-2a [40 kD]) plus Copegus® (ribavirin).
This treatment course is only for patients with particular strains of chronic hepatitis C, that is, genotype 2 or 3. Other requirements are that the patients have low levels of the virus before starting treatment and show a rapid response by clearing the virus from their blood within 4 weeks of treatment.
The EU approval also marks a key milestone in Roche‘s (Basel, Switzerland) implementation of a new treatment concept in hepatitis C, which is called ‘response-guided therapy‘ and seeks to customize regimens for patients based on how well they respond to treatment.
“Response-guided therapy in hepatitis C is an excellent example of how Roche is uniquely positioned to individualize healthcare and deliver real benefit to patients, physicians and healthcare payers by combining the power of innovative pharmaceuticals and diagnostics”, commented William M Burns, CEO of Roche‘s Pharmaceuticals Division.
“This approval for 16 weeks of treatment in genotype 2 and 3 patients with a rapid response demonstrates the value of using diagnostic tools to determine an individual treatment regimen and hopefully will encourage more eligible patients to come forward for treatment. Together with the start of yet another large clinical study with Pegasys, Enhancement of Cure Through Treatment Extension Guided by On-Treatment Response in Patients Infected with G2/3 Hepatitis C (NCORE), these initiatives underscore Roche‘s commitment to advancing the treatment of hepatitis and making personalized medicine a reality”.
Source: Roche press release www.roche.com/med-cor-2008-06-26
Mutant RAS Found to Modify Leukemia Patients‘ Response to Cytarabine Therapy
Cancer researchers at the Ohio State University Comprehensive Cancer Center (OH, USA), have recently published a study that examined whether RAS mutations found in acute myeloid leukemia (AML) patients may have an impact on the response to cytarabine in vivo.
The researchers screened 185 AML patients (aged 60 years or younger), who had achieved complete remission following initial anticancer therapy from the Cancer and Leukemia Group B study, for RAS mutations. They found that 18% (34) of the patients had mutations in the RAS gene, of which, 22 patients had received high-dose cytarabine and 12 patients had received a low dose of the drug.
“This appears to be the first example in AML of a mutation in an oncogene that favorably modifies a patient‘s response to the dose of a routinely used chemotherapeutic drug”, explained Clara D Bloomfield, an internationally known AML specialist and distinguished university professor, and the William G Pace III Professor in Cancer Research at Ohio State University.
The results demonstrated that the lowest relapse rate group included patients who had received high doses of the drug and were also found to have RAS mutations. A total of 45% of these patients experienced disease recurrence after an average 10-year follow-up compared with 68% of patients with normal RAS genes. “That means 55% of patients with RAS mutations were cured compared with 32% of high-dose patients with normal RAS”, explained Bloomfield. A total of 80% of the patients with normal RAS genes were found to relapse as well as the patients who had received low does of cytarabine and who also had RAS mutations.
“These data strongly suggest that mutations in RAS influence the response of AML patients to high-dose cytarabine, and they support the use of these mutations as biomarkers for this therapy”, concluded Bloomfield.
Source: Neubauer A, Maharry K, Mrózek K et al.: Patients with acute myeloid leukemia and RAS mutations benefit most from postremission high-dose cytarabine: a Cancer and Leukemia Group B Study. J. Clin. Oncol. (2008) (Epub ahead of print).
Targeted Therapy for Colorectal Cancer May be Possible by Evaluating KRAS Status
Promising studies for personalizing anticancer therapy for metastatic colorectal cancer (mCRC) were recently presented at the annual American Society for Clinical Oncology conference, which was held in Chicago (IL, USA) in May 2008.
Results from a randomized Phase III trial were presented by investigators from the University Hospital Gasthuisberg (Leuven, Belgium) and colleagues. The results of the study revealed that patients who had colorectal tumors that expressed normal KRAS showed better clinical responses when a cetuximab-based regimen was used as first-line therapy.
Eric van Cutsem, one of the study‘s lead authors, explained that “KRAS is the first molecular marker for the selection of a targeted therapy in combination with a standard chemotherapy regimen in first-line mCRC. Patients with KRAS wild-type tumors have a strong benefit from the combination of cetuximab and FOLFIRI [leucovorin, fluorouracil and irinotecan]. Cetuximab in combination with a standard first-line treatment for patients with mCRC is an important new option in patients with KRAS wild-type tumors.”
The investigators isolated genomic DNA from the available archival tumor samples that came from 540 of the total 1198 patients who were involved in the study to re-evaluate the clinical responses based on KRAS expression (either wild-type or mutant) in the tumor. The tumor samples were tested for the common mutation found in the KRAS gene at codon 12/13. This mutation was detected in 192 samples with a 36% frequency, which was similar to the frequency found in other studies. Progression-free survival and overall objective responses were highest in patients with tumors expressing normal KRAS and receiving a combination of cetuximab plus FOLFIRI therapy.
The data from the study have helped to clarify the biology of tumors expressing KRAS mutations and have also helped to advance the use of cetuximab as the first-line treatment of mCRC with normal KRAS expression.
The findings of this study have also been corroborated with information from another three randomized, controlled studies.
The implications of the findings are immense for clinical practice and the potential for personalizing anticancer therapy. But the researchers stress that the current chemotherapy regimens must remain active in treating this disease, and this information must be conveyed to patients with tumors containing KRAS mutations.
Source: van Cutsem E, Lang I, D‘haens G et al.: KRAS status and efficacy in the first-line treatment of patients wi th metastatic colorectal cancer (mCRC) treated with FOLFIRI with or without cetuximab: the CRYSTAL experience. J. Clin. Oncol. 26(Suppl.), Abstract 2 (2008).