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Thursday, May 26, 2016

The outcomes of chronic myeloid leukemia (CML) have dramatically improved as the result of tyrosine kinase inhibitor (TKI) treatment. Use of a TKI regimen can lower the blood CML biomarker to levels imperceptible by current detection methods. For patients in "molecular remission," however, uncertainties remain regarding whether they will relapse or if treatment should be discontinued. A study in The Journal of Molecular Diagnostics described a new personalized DNA-based digital assay that detects persistent disease in 81 percent of samples taken from a group of patients thought to be in remission.

"If validated in clinical trials of stopping TKIs, this technique will permit a more personalized approach to recommendations for dose reduction or drug cessation in individual patients, ensuring that therapy is withdrawn only from patients with the highest chance of long-term remission," explained lead investigator and head of department Jane F. Apperley, MD, PhD, FRCPath, of the Centre for Haematology, Imperial College (London). Indeed, studies have shown 60 percent of CML patients who achieve sustained undetectable levels of BCR-ABL1 transcripts—the hallmark biomarker of CML—experience disease recurrence after TKI treatment is withdrawn.

Investigators compared the sensitivity of the new technique, DNA-based digital PCR (dPCR) assay, to three other quantitative PCR methods currently used to measure residual CML, including reverse transcriptase-quantitative PCR (RT-qPCR), quantitative PCR (qPCR), and reverse transcriptase-digital PCR (RT-dPCR). RT-qPCR is currently the most widely used method for monitoring residual disease in CML patients.

Thirty-six samples were taken from six patients with early CML who were thought to be in deep molecular remission, as indicated by RT-qPCR results. Repeat analysis using dPCR with preamplification detected persistent disease in 81% of the samples. In comparison, the detection rate was 25% using RT-dPCR and 19% for qPCR. "We conclude that dPCR for BCR-ABL1 DNA is the most sensitive available method of residual disease detection in CML and may prove useful in the management of TKI withdrawal," stated Dr. Apperley.

The new assay has the potential to dramatically impact CML management. Immediately after CML diagnosis, the patient's genomic breakpoints would be identified, enabling the design of a patient-specific assay. The patient's response to therapy would be monitored using standard RT-qPCR until reaching molecular remission. At that point, routine monitoring would be augmented with dPCR, allowing better-informed treatment decisions and improved patient management.

According to Apperley, the new method improves on previous methodologies in two key areas. First, dPCR is a DNA-based method that allows identification of BCR-ABL1 fusion junctions by targeted next-generation sequencing. This enables the rapid generation of high-performing DNA-based hydrolysis probe assays that are specific to the individual molecular footprint of each patient's CML clone, although the number and location of fusion junctions may vary among patients. The second advancement afforded by the new method relates to the greater sensitivity provided by the dPCR platform. "The technique we describe, with which we successfully mapped a disease-specific junction in all patients tested, is relatively simple, cost effective, and suited to a high-throughput laboratory," noted Apperley.


Thursday, May 26, 2016

Noninvasive cell-tracking methods are indispensable for assessing the safety and efficacy of stem-cell based therapy. Thus, the research of noninvasive cell-tracking methods for determining in vivo the translocation and long-term viability of the transplanted stem cells have received considerable attention. A recent review article summarized the recent progress in tracking the viability of the transplanted stem cells in vivo.

In the article by researchers at Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, and College of Biological Science and Technology, Fuzhou University, summarized the current methods for tracking the viability of the transplanted stem cells in vivo, including reporter-gene based methods, exogenous contrast label-based methods and multimodel imaging methods.

In the past decades, stem cell-based regenerative medicine has attracted intense attention and extraordinary expectation due to its potentials in the treatment of numerous major diseases, such as hepatic, cardiac, pulmonary, renal, and neurological diseases. Clearly knowing the viability, distribution and differentiation of the transplanted stem cells in vivo is a prerequisite for better understanding the role of stem cells playing in the therapeutic process, in which the survival report of the transplanted stem cells in vivo is particularly crucial in determining the success of stem cell-based regenerative medicine.

Therefore, the development of non-invasive imaging methods that can in situ monitor the viability of the transplanted stem cells is urgently needed. In this article, the authors summarized the development history of stem cell-tracking imaging techniques, explained the imaging principles, pros and cons underlying these techniques, and provided an overview of the applications of these techniques in animal models or humans. Furthermore, this review provided a guide line for researchers to select the right tracking method for the right study. Finally, this review discussed the current challenges in tracking the viability of transplanted stem cells, and emphasized the promise of the combined NIR-II fluorescence imaging/BLI method and MRI/PET method for further applications in high-throughput cell therapy screening in animal models and safe imaging in clinical trials, respectively.

The authors wrote "To the best of our knowledge, this review represents the firsthand knowledge of the current methodologies for in vivo tracking the viability of transplanted stem cells, and provides a guide line for further researches in in vivo cell viability tracking."


Thursday, May 26, 2016

The ability to reprogram cells has revolutionized stem cell research with major implications for almost all fields of modern biology. A decade ago Shinya Yamanaka described a procedure that revolutionized stem cell biology. Using a genetic trick that introduces a cocktail of four genes into cultured cells from human biopsies, he was able to generate induced pluripotent stem cells (iPS) from mature skin or blood cells.

iPS cells are similar to embryonic stem cells and can be re-transformed into skin cells and blood, but also into nerve cells and other cells in the body, making them highly attractive for regenerative medicine. Many laboratories around the world are using patient-derived iPS cells to study the patient's disease in a dish and to develop compounds to treat the disease. Other laboratories are studying how such "reprogramming" works to improve current protocols to generate high-quality iPS cells for cell-based therapy. Until now, these studies have been hampered by the fact that in biopsy-derived cultures only few cells convert into iPS cells and those that do, called 'elite cells', cannot be recognized before they are converted.

Now, a European team of scientists led by senior group leader Thomas Graf, PhD, and his laboratory at the Centre for Genomic Regulation in Barcelona, Spain, have made a big step toward creating such elite cells, discovering a surprising connection between iPS cell reprogramming, blood cell formation in the body, and blood cancer.

In previous work, the Graf laboratory found that introduction of a protein called C/EBPa into mouse lymphocytes, which are immune cells, almost magically turns them into elite cells for reprogramming by the Yamanaka cocktail. Both C/EBPa and the four Yamanaka factors are so called transcription factors: proteins that bind to specific sequences in the DNA, thereby turning the activity of genes embedded in chromatin on or off. Changes in gene expression are essential for cell reprogramming, since genes important for stem cell functions must be turned on, while genes important for the starting cells or its specialization must be turned off.

In work now published in Nature Cell Biology, researchers found that C/EBPa changes the chromatin and the proteome of B-lymphocytes to make it receptive to the action of the Yamanaka factors. "We have made major advances to understand how C/EBPa contributes to cell reprogramming, allowing us to obtain elite cells in a highly effective manner. We also found that such artificially created elite cells are very similar to white blood cell progenitors in the bone marrow called 'GMPs' or myeloblasts, which themselves require C/EBPa for their formation," explained Graf.

Importantly, GMPs are also a sort of "elite cells" for cancer, as animals in which C/EBPa is removed become resistant to the development of acute myeloblastic leukemia since their myeloblasts are unable to respond to oncogenes required for tumor formation. The new studies therefore showed the transcription factor C/EBPa establishes a connection between the formation of pluripotent stem cells, the specification of blood cells in the bone marrow, and the generation of myeloblastic cancer cells.

"Our findings may have implications for both the improvement of protocols to generate stem cells needed in regenerative medicine and the discovery of new targets for treatment of myeloid leukemia" stated Bruno Di Stefano, PhD, co-first author of this work at Graf's laboratory in the Centre for Genomic Regulation, and currently working at Harvard University, Boston. "Our work sheds new light on how changes in protein stability and chromatin accessibility influence cell proliferation and cancer," added Janus Jakobsen, PhD, co-first author of this work.


Wednesday, May 18, 2016

Up to 50 percent of patients with soft tissue sarcoma (STS) develop lung metastases. Effective systemic therapies for metastatic STS are currently limited; when possible, surgical removal of the lung metastases (known as pulmonary metastasectomy, PM) is the preferred treatment. However, guidelines for the performance of PM for STS do not exist and decisions to operate are often made on an individual basis. In a presentation at the 96th AATS Annual Meeting, researchers from Memorial Sloan Kettering Cancer Center share the results of their experience with more than 500 patients with pulmonary metastases from STS and describe prognostic factors associated with improved survival.

Approximately 12,000 new cases of STS are diagnosed in the U.S. annually, resulting in nearly 5,000 deaths. Up to half of STS patients develop one or more lung metastases. Without effective systemic therapies, doctors often rely on pulmonary metastasectomy (PM), surgical removal of the pulmonary metastases, although current data for the practice specific to STS are limited. In a presentation at the 96th AATS Annual meeting, Neel P. Chudgar, MD, from the Department of Surgery at Memorial Sloan Kettering Cancer Center presented survival data and prognostic factors based on a large, single-institution database of STS patients who have undergone pulmonary metastasectomy.

"The present study differs from previous publications in that we used a larger single-institution cohort, which increases the power to potentially identify significant differences, and we focused on STS exclusively to enhance the homogeneity of the study population," explained Chudgar. The database included 803 patients who underwent PM for sarcoma between September 1991 and June 2014. After excluding patients who had primary bone sarcomas, underwent diagnostic resection, underwent PM at another hospital, or did not undergo resection of their primary tumor, 539 patients who underwent 760 curative-intent PMs were studied.

The investigators found the median overall survival after the first PM was 33.2 months and the median disease-free survival was 6.8 months. Thirty-four percent of patients were alive after 5 years and 23 percent were alive after 7 years.

The researchers then analyzed the data to see if they could identify factors associated with prolonged survival. They found that leiomyosarcoma histologic subtype, primary tumor size less than or equal to 10 cm, increasing time from primary tumor resection to development of pulmonary metastases, and less than or equal to three initial lung metastases, were all significantly associated with longer overall survival. Minimally invasive resections were also associated with longer overall survival (median, 44.3 months), compared with open surgery (median, 29.9 months). However, the authors attribute the reduced risk associated with minimally invasive surgery to patient selection, since 81 percent of these patients had only one or two pulmonary metastases.

"Our results indicate that the preoperative determination of disease characteristics can assist surgeons in selecting patients who may achieve longer survival with PM," commented senior author David R. Jones, MD, Professor and Chief of the Thoracic Surgery Service at Memorial Sloan Kettering Cancer Center. "Until there is an improved understanding of the underlying biologic mechanisms of metastases and further identification of druggable targets, PM remains the best available treatment for metastatic STS."

Wednesday, May 18, 2016

On May 17, 2016, the FDA granted accelerated approval to nivolumab (Opdivo) for the treatment of patients with classical Hodgkin lymphoma (cHL) that has relapsed or progressed after autologous hematopoietic stem cell transplantation (HSCT) and post-transplantation brentuximab vedotin (Adcetris).

The approval was based on two single-arm, multicenter trials of nivolumab in adults with relapsed or refractory cHL. The trials enrolled patients regardless of PD-L1 expression status on Reed-Sternberg cells. The primary efficacy endpoint was objective response rate (ORR) as determined by an independent radiographic review committee.  Additional outcome measures included duration of response (DOR).
Efficacy was evaluated in 95 patients previously treated with autologous HSCT and post-transplantation brentuximab vedotin. Patients had a median of five prior systemic regimens (range: 3, 15) and received a median of 17 doses of nivolumab (range: 3, 48). Single-agent nivolumab produced a 65 percent ORR (95% CI: 55%, 75%), with 58 percent partial remission and 7 percent complete remission. The median time-to-response was 2.1 months (range: 0.7 to 5.7 months).  The estimated median DOR was 8.7 months.
Safety was evaluated in 263 patients with relapsed or refractory cHL. Ninety-eight percent of patients had received autologous HSCT. Patients received a median of 10 doses of nivolumab (range: 1, 48) at the approved dose-schedule. The most common (reported in at least 20%) adverse reactions of any grade were fatigue, upper respiratory tract infection, cough, pyrexia, and diarrhea.  Additional common adverse reactions (reported in at least 10%) included rash, pruritus, musculoskeletal pain, nausea, vomiting, abdominal pain, headache, peripheral neuropathy, arthralgia, dyspnea, infusion-related reactions, and hypothyroidism or thyroiditis.
Other immune-mediated adverse reactions, occurring in 1 percent to 5 percent of patients, included rash, pneumonitis, hepatitis, hyperthyroidism, and colitis. Serious adverse reactions were reported in 21 percent of patients. The most common SAEs, reported in 1 percent to 3 percent of patients, were pneumonia, pleural effusion, pneumonitis, pyrexia, infusion-related reaction, and rash.
A new “Warning and Precaution” was issued for complications of allogeneic HSCT after nivolumab. Transplant-related deaths have occurred, and health care professionals should follow patients closely for early evidence of transplant-related complications, such as hyperacute graft-versus-host disease (GVHD), severe acute GVHD, steroid-requiring febrile syndrome, hepatic veno-occlusive disease, and other immune-mediated adverse reactions. FDA has required the manufacturer to further study the safety of allogeneic HSCT after nivolumab.
The recommended dose-schedule of nivolumab is 3 mg/kg intravenously every 2 weeks until disease progression or unacceptable toxicity.
Continued approval for the cHL indication may be contingent upon verification of clinical benefit through a randomized phase III trial.
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