Tag: Medication

As spindly, elongated cells, neurons must be able to transport proteins and receptors between distant sites in their cell bodies and axons to function properly. A new imaging study by researchers at Johns Hopkins University has now visualized the ebb and flow of the nerve growth factor receptor TrkA within neurons, via an unusual process known as transcytosis. Their study also explains how this phenomenon supports neuronal function and connectivity in mice.

Senior and corresponding author Rejji Kuruvilla, PhD, at Johns Hopkins University Department of Biology, and colleagues reported on their findings in Science Signaling, in a paper titled “Transcytosis-mediated anterograde transport of the receptor TrkA mediates the formation of presynaptic sites in sympathetic neurons.” In their paper, the authors concluded, “These findings provide mechanistic insight into an atypical mode of receptor trafficking and demonstrate its physiological relevance in sympathetic neuron connectivity in mice … Our study suggests that transcytosis might be a more general mechanism than now appreciated for the targeted transport of trophic and guidance receptors, adhesion and synaptic proteins, as well as ion channels.”

The axons of neurons are extremely long compared to their main cell bodies, with axon terminals sometimes residing a long distance from the cell nucleus. “Axon terminals can be meters away from cell bodies where many axonal membrane proteins with critical functions in regulating axon guidance and growth, neuronal survival, presynaptic organization, and synaptic transmission are made,” the authors wrote.

Neurons need to be able to transport these proteins efficiently across these relatively vast distances. They do this by either directly sending the protein through a secretory pathway or via an indirect mechanism called transcytosis. The latter occurs when the central cell body takes in newly synthesized proteins or surface receptors, after which they move to axons through the cell cytoplasm. “Transcytosis is an atypical endocytosis-based mechanism, where newly synthesized proteins are first inserted on cell body surfaces, internalized, and anterogradely transported to axons,” the team continued.

Transcytosis is still relatively obscure and enigmatic compared with the direct secretion method, and questions remain about how exactly it sustains the function and connectivity of neurons. “In contrast to the considerable progress made in understanding the direct secretory pathway, there is limited knowledge about transcytosis, specifically the underlying transport kinetics and organelles involved, whether it occurs in vivo, and its contributions to neuronal connectivity and function,” the investigators noted.

Seeking answers, first author Kuruvilla, together with first author Guillermo Moya-Alvarado, PhD, and colleagues, used live cell imaging and electron microscopy to peer at the movement of receptors across compartments within mouse neurons.

They visualized the trafficking dynamics and transcytosis of a receptor named TrkA. “The family of tropomyosin-related kinase (Trk) receptors provides a prominent example of membrane proteins that undergo long-distance axonal trafficking to control neuronal survival, axon growth, and synaptic transmission,” the scientists explained.

Through their study, the authors noted various shifts in speed and direction as vesicles carried TrkA from the soma to axons. Using labeled TrkA proteins, the scientists also confirmed that transcytosis occurred within nerve terminals of living mice. “Live imaging and electron microscopy of compartmentalized cultures revealed that soma surface–derived TrkA proteins underwent dynamic transport within axons, with changes in speed, direction, and the vesicular organelles that carried them as they moved from proximal to distal axon compartments,” they stated. “In mice, soma surface–labeled TrkA proteins were observed in sympathetic nerve terminals, demonstrating that transcytosis occurs in vivo.”

They also found that disrupting its transcytosis by introducing a point mutation into TrkA reduced the number and size of presynaptic sites and decreased synaptic transmission in culture and in rodents in vivo, confirming the importance of the process for neuronal physiology.  “These findings provide mechanistic insight into an atypical mode of receptor trafficking and demonstrate its physiological relevance in sympathetic neuron connectivity in mice,” the team concluded “Uncovering mechanisms of axon delivery has implications that extend beyond the healthy nervous system to understanding cell biological pathways that contribute to nerve repair after injury or neurodegeneration, because the correct complement of membrane proteins must be accurately targeted to regenerating axons to ensure functional recovery.”

The post Visualizing Receptor Transport Within Neurons via Transcytosis appeared first on GEN – Genetic Engineering and Biotechnology News.

A personalized DNA vaccine targeting up to 40 patient-specific neoantigens generated robust immune responses and encouraging survival outcomes in patients with MGMT-unmethylated glioblastoma in a small Phase I clinical trial, according to new findings published in Nature Cancer.

The study evaluated GNOS-PV01, a personalized therapeutic cancer vaccine developed by Geneos Therapeutics in collaboration with researchers at Washington University School of Medicine in St. Louis. Investigators reported that the vaccine was safe, feasible to administer, and capable of stimulating circulating and tumor-infiltrating T-cell responses in a cancer type long considered highly resistant to immunotherapy.

Glioblastoma remains one of the deadliest cancers, with median survival typically ranging from 12 to 18 months. Patients with MGMT-unmethylated disease face especially poor outcomes because they derive limited benefit from temozolomide, a standard chemotherapy agent commonly used after surgery and radiation.

“Nothing really works in this MGMT-negative or unmethylated glioblastoma patient population,” said Niranjan Sardesai, Geneos’ CEO. “Median survival is around a year, and effective treatments are very much needed.”

The open-label, single-arm GT-20 study enrolled nine patients with newly diagnosed MGMT-unmethylated glioblastoma following surgical resection and radiation therapy. Each patient received a fully individualized vaccine constructed from neoantigens identified through sequencing of their own tumors. Vaccines encoded between 17 and 40 neoantigens per patient.

According to the paper, the vaccine caused no serious adverse events, unexpected toxicities, or dose-limiting toxicities. Eight of the nine evaluable patients developed measurable immune responses. The lone nonresponder had been treated with dexamethasone, an immunosuppressive corticosteroid frequently used in glioblastoma management.

Sardesai emphasized that the immunogenicity findings were particularly notable because glioblastoma is considered an “immune-excluded” tumor with low tumor mutational burden, characteristics that have historically limited the effectiveness of checkpoint inhibitors such as anti–PD-1 therapies.

“Checkpoint-based immunotherapy has not worked in GBM,” he said. “This is a cold tumor.”

The investigators also observed signals of clinical activity. Six-month progression-free survival and 12-month overall survival were each achieved in 66.7% of patients. Median progression-free survival was 8.5 months, while median overall survival reached 16.3 months. Survival at 24 months was 33%, including one patient who remains alive four years after surgery.

“What was very striking was that three of nine patients, or one-third of the patients, had lived more than two years,” Sardesai said. “The two-year survival rate is about 10% to 15%” with standard treatment approaches in this population.

The study also identified an association between stronger CD8-positive T-cell responses and longer survival. Investigators reported that patients generating higher levels of vaccine-induced cytotoxic T cells tended to experience improved overall survival.

One of the most compelling findings involved a long-term survivor who has remained progression-free for nearly five years. Researchers analyzed a brain biopsy obtained approximately three years after treatment initiation and identified vaccine-induced T-cell clones within the tumor tissue that matched T-cell populations detected in the patient’s blood.

“For the first time, we are able to match vaccine-driven immune responses,” Sardesai said. “We are able to see T-cell clones in the blood, and these T-cell clones have infiltrated and are found in her brain.”

The vaccine platform differs from earlier glioblastoma vaccine strategies in several ways. Rather than targeting a small number of antigens, the DNA-based approach allows investigators to incorporate a much larger neoantigen repertoire into each personalized product.

“These patients received as many as 40 different antigens that were identified from their own tumor,” Sardesai said. “Prior treatments had typically been looking at 20 or fewer in GBM.”

He argued that broader antigen targeting may be especially important in glioblastoma because of the disease’s pronounced intratumoral heterogeneity.

“When it comes to targeting cancer, more is better,” he said. “You want to take more shots on goal.”

Another distinguishing feature of the platform is its apparent ability to stimulate CD8-positive killer T cells, which are considered critical for direct tumor cell elimination. Sardesai noted that generating robust CD8 responses has historically been difficult for many cancer vaccine technologies.

Importantly, each vaccine is uniquely manufactured for a single patient.

“These are exquisitely personalized vaccines,” Sardesai said. “Every patient gets their own vaccine.”

The authors cautioned that the findings remain preliminary because of the trial’s small sample size and lack of a control arm. Still, they believe the results justify larger randomized studies.

“We are very encouraged by the data,” Sardesai said. “But this is still only nine patients. We have to replicate these findings in larger, well-controlled studies.”

The company has previously reported results using the same platform in hepatocellular carcinoma, suggesting the strategy could potentially extend across multiple tumor types characterized by immune exclusion and low tumor mutational burden.

“All cancers carry neoantigens,” Sardesai said. “These personalized cancer vaccines provide a very convenient way” to target those tumor-specific alterations across different cancers.

The post Personalized DNA Vaccine Shows Immune Activation and Survival Signals in Glioblastoma Trial appeared first on Inside Precision Medicine.