Tag: Dennis Discher

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The Physics of Fat Droplets Reveal DNA Danger

by Devorah Fischler

Fat is a normal and necessary part of the body. Fat cells store and release energy, as well as play significant roles in hormonal regulation and immunity.

Engineers and scientists at the University of Pennsylvania are the first to discover fat-filled lipid droplets’ (pictured above in green) surprising capability to indent and puncture the nucleus, the organelle which contains and regulates a cell’s DNA.

In recent decades, a concerning rise in metabolic illnesses – such as cardiovascular disease, high blood pressure and diabetes – has focused scientific attention on the biology and chemistry of fat, resulting in a wealth of information about how fat cells work.

But fat cells and their metabolic activities are only part of the story.

Fat-filled lipid droplets, tiny spheres of fat many times smaller than fat cells, are a growing subject of scientific interest. Found inside many different cell types, these lipid particles have long been little understood. Studies have begun to illuminate these droplets’ participation in metabolic functions and cellular protection, but we still know next to nothing about the physical nature of fat.

Now, researchers at the University of Pennsylvania School of Engineering and Applied Science have looked beyond biochemistry to publish groundbreaking work on the physics of these droplets, revealing them to be a potential threat to a cell’s nucleus. In the August issue of the Journal of Cell Biology, they are the first to discover fat-filled lipid droplets’ surprising capability to indent and puncture the nucleus, the organelle which contains and regulates a cell’s DNA.

The stakes of their findings are high: a ruptured nucleus can lead to elevated DNA damage that is characteristic of many diseases, including cancer.

The study was led by Dennis E. Discher, Robert D. Bent Professor in the Department of Chemical and Biomolecular Engineering, Bioengineering, and in Mechanical Engineering and Applied Mechanics, Irena Ivanovska, Ph.D. research associate in Penn’s Molecular and Cell Biophysics Lab, and Michael Tobin, Ph.D. candidate in the Department of Bioengineering.

“Intuitively, people think of fat as soft,” says Discher. “And on a cellular level it is. But at this small size of droplet— measuring just a few microns rather than the hundreds of microns of a mature fat cell—it stops being soft. Its shape has a much higher curvature, bending other objects very sharply. This changes its physics in the cell. It can deform. It can damage. It can rupture.”

Read the full story in Penn Engineering Today.

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Engineered White Blood Cells Eliminate Cancer

by Melissa Pappas

“Macrophages killing cancer cell” photographed by Susan Arnold.

By silencing the molecular pathway that prevents macrophages from attacking our own cells, Penn Engineers have manipulated these white blood cells to eliminate solid tumors.

Cancer remains one of the leading causes of death in the U.S. at over 600,000 deaths per year. Cancers that form solid tumors such as in the breast, brain or skin are particularly hard to treat. Surgery is typically the first line of defense for patients fighting solid tumors. But surgery may not remove all cancerous cells, and leftover cells can mutate and spread throughout the body. A more targeted and wholistic treatment could replace the blunt approach of surgery with one that eliminates cancer from the inside using our own cells.

Dennis Discher, Robert D. Bent Professor in Chemical and Biomolecular Engineering, Bioengineering, and Mechanical Engineering and Applied Mechanics, and postdoctoral fellow, Larry Dooling, provide a new approach in targeted therapies for solid tumor cancers in their study, published in Nature Biomedical Engineering. Their therapy not only eliminates cancerous cells, but teaches the immune system to recognize and kill them in the future.

“Due to a solid tumor’s physical properties, it is challenging to design molecules that can enter these masses,” says Discher. “Instead of creating a new molecule to do the job, we propose using cells that ‘eat’ invaders – macrophages.”

Macrophages, a type of white blood cell, immediately engulf and destroy – phagocytize – invaders such as bacteria, viruses, and even implants to remove them from the body. A macrophage’s innate immune response teaches our bodies to remember and attack invading cells in the future. This learned immunity is essential to creating a kind of cancer vaccine.

But, a macrophage can’t attack what it can’t see.

“Macrophages recognize cancer cells as part of the body, not invaders,” says Dooling. “To allow these white blood cells to see and attack cancer cells, we had to investigate the molecular pathway that controls cell-to-cell communication. Turning off this pathway – a checkpoint interaction between a protein called SIRPa on the macrophage and the CD47 protein found on all ‘self’ cells – was the key to creating this therapy.”

Read the full story in Penn Engineering Today.

Multiple members in the biophysical engineering lab lead by Dennis Discher, including co-lead author and postdoctoral fellow and Penn Bioengineering alumnus Jason Andrechak and Bioengineering Ph.D. student Brandon Hayes, contributed to this study. The research was funded by grants from the National Heart, Lung, and Blood Institute and the National Cancer Institute, including the Physical Sciences Oncology Network, of the US National Institutes of Health.

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New Insights into the Mechanisms of Tumor Growth

by Nathi Magubane

3d render of cells secreting exosomes
A team of researchers led by the School of Arts & Science’s Wei Guo offers new insights into a mechanism that promotes tumor growth. “This information could be used to help clinicians diagnose cancers earlier in the future,” says Guo.

In many instances, the physical manifestation of cancers and the ways they are subsequently diagnosed is via a tumor, tissue masses of mutated cells and structures that grow excessively. One of the major mysteries in understanding what goes awry in cancers relates to the environments within which these structures grow, commonly known as the tumor microenvironment.

These microenvironments play a role in facilitating tumor survival, growth, and spread. Tumors can help generate their own infrastructure in the form of vasculature, immune cells, signaling molecules, and extracellular matrices (ECMs), three-dimensional networks of collagen-rich support scaffolding for a cell. ECMs also help regulate cellular communications, and in the tumor microenvironment ECMs can be a key promoter of tumor growth by providing structural support for cancerous cells and in modulating signaling pathways that promote growth.

Now, new research led by the School of Arts & Science’s Wei Guo and published in the journal Nature Cell Biology has bridged the complex structural interactions within the tumor microenvironment to the signals that trigger tumor growth. The researchers studied cancerous liver cells grown on ECMs of varying stiffness and discovered that the stiffening associated with tumor growth can initiate a cascade that increases the production of small lipid-encapsulated vesicles known as exosomes.

“Think of these exosomes as packages that each cell couriers out, and, depending on the address, they get directed to other cells,” says Ravi Radhakrishnan, professor of bioengineering in the School of Engineering and Applied Science and a co-author of the paper.

“By recording the number of packages sent, the addresses on these packages, their contents, and most importantly, how they’re regulated and generated, we can better understand the relationship between a patient’s tumor microenvironment and their unique molecular signaling signatures, hinting at more robust personalized cancer therapies,” Radhakrishnan says.

While studying exosomes in relation to tumor growth and metastasis has been well-documented in recent years, researchers have mostly focused on cataloging their characteristics rather than investigating the many processes that govern the creation and shuttling of exosomes between cells. As members of Penn’s Physical Sciences Oncology Center (PSOC), Guo and Radhakrishnan have long collaborated on projects concerning tissue stiffness. For this paper, they sought to elucidate how stiffening promotes exosome trafficking in cancerous intracellular signaling.

“Our lab previously found that high stiffness promotes the secretion of exosomes,” says Di-Ao Liu, co-first author of the paper and a graduate student in the Guo Lab. “Now, we were able to model the stiffening processes through experiments and identify molecular pathways and protein networks that cause this, which better links ECM stiffening to cancerous signaling.”

Read the full story in Penn Today.

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Bioengineering Graduate Jason Andrechak Wins Graduate Leadership Award

Jason Andrechak

Congratulations to recent Penn Bioengineering graduate Jason Andrechak on winning a Graduate Leadership Awards for 2022. Each year a select number of students across the university are recognized for their service and lasting contributions to graduate student life at Penn. Andrechak, one of only ten recipients in 2022, won a Dr. Andy Binns Award for Outstanding Service to Graduate and Professional Student Life. This award is presented to “graduate or professional students, upon their graduation from Penn, who have significantly impacted graduate and professional student life through service involvement in student life initiatives or organizations.” Andrechak won this award for his “service and leadership in advocating for equity and accessibility during the transition to virtual operations and following a period of leadership transition within the Graduate and Professional Student Assembly (GAPSA). ”

Andrechak completed his Ph.D. in Bioengineering in 2022, where he studied macrophage immunotherapy in solid tumors in the lab of Dennis E. Discher, Robert D. Bent Professor in Chemical and Biomolecular Engineering, Bioengineering, and Mechanical Engineering and Applied Mechanics. He was named a National Science Foundation Graduate Research Fellow in 2018. He has actively led the Graduate Association of Bioengineers (GABE) as Community Service & Outreach chair from 2017-2019 and as co-President from 2019-2022. He also served as the Director of Equity & Access for the Graduate & Professional Student Assembly (GAPSA) from 2020-2021, in addition to several other service and advisory roles at the department, school, and university levels.

Learn more about the Penn Graduate Leadership Awards and read the full list of recipients on the Grad Center at Penn website.

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Penn Anti-Cancer Engineering Center Will Delve Into the Disease’s Physical Fundamentals

by Evan Lerner

A colorized microscope image of an osteosarcoma shows how cellular fibers can transfer physical force between neighboring nuclei, influencing genes. The Penn Anti-Cancer Engineering Center will study such forces, looking for mechanisms that could lead to new treatments or preventative therapies.

Advances in cell and molecular technologies are revolutionizing the treatment of cancer, with faster detection, targeted therapies and, in some cases, the ability to permanently retrain a patient’s own immune system to destroy malignant cells.

However, there are fundamental forces and associated challenges that determine how cancer grows and spreads. The pathological genes that give rise to tumors are regulated in part by a cell’s microenvironment, meaning that the physical push and pull of neighboring cells play a role alongside the chemical signals passed within and between them.

The Penn Anti-Cancer Engineering Center (PACE) will bring diverse research groups from the School of Engineering and Applied Science together with labs in the School of Arts & Sciences and the Perelman School of Medicine to understand these physical forces, leveraging their insights to develop new types of treatments and preventative therapies.

Supported by a series of grants from the NIH’s National Cancer Institute, the PACE Center is Penn’s new hub within the Physical Sciences in Oncology Network. It will draw upon Penn’s ecosystem of related research, including faculty members from the Abramson Cancer Center, Center for Targeted Therapeutics and Translational Nanomedicine, Center for Soft and Living Matter, Institute for Regenerative Medicine, Institute for Immunology and Center for Genome Integrity.

Dennis Discher and Ravi Radhakrishnan

The Center’s founding members are Dennis Discher, Robert D. Bent Professor with appointments in the Departments of Chemical and Biomolecular Engineering (CBE), Bioengineering (BE) and Mechanical Engineering and Applied Mechanics (MEAM), and Ravi Radhakrishnan, Professor and chair of BE with an appointment in CBE.

Discher, an expert in mechanobiology and in delivery of cells and nanoparticles to solid tumors, and Radhakrishnan, an expert on modeling physical forces that influence binding events, have long collaborated within the Physical Sciences in Oncology Network. This large network of physical scientists and engineers focuses on cancer mechanisms and develops new tools and trainee opportunities shared across the U.S. and around the world.

Lukasz Bugaj, Alex Hughes, Jenny Jiang, Bomyi Lim, Jennifer Lukes and Vivek Shenoy (Clockwise from upper left).

Additional Engineering faculty with growing efforts in the new Center include Lukasz Bugaj, Alex Hughes and Jenny Jiang (BE), Bomyi Lim (CBE), Jennifer Lukes (MEAM) and Vivek Shenoy (Materials Science and Engineering).

Among the PACE Center’s initial research efforts are studies of the genetic and immune mechanisms associated with whether a tumor is solid or liquid and investigations into how physical stresses influence cell signaling.

Originally posted in Penn Engineering Today.

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Getting Physical with Developmental Biology Research

macrophages Discher
Dennis Discher, Ph.D.

By Izzy Lopez

While genetics and biochemistry research has dominated the conversation about how human bodies are formed, new research — with an old twist — is proposing that there is another star in the show of human development: mechanical forces.

At the turn of the twentieth century, medical research relied on simple mechanics to explain scientific phenomena, including how human cells morph into shape from embryo to newborn and beyond. As better chemistry techniques and DNA research burst onto the scene, however, the idea that cells could be affected by physical forces took a back seat. Now researchers are referring back to this vintage idea and bringing it into the 21st century.

Dennis Discher, Robert D. Bent Professor in the Departments of Chemical and Biomolecular Engineering, Bioengineering and Mechanical Engineering and Applied Mechanics, was featured in a recent article in Knowable Magazine for his research on the human heart and how mechanical forces exerted on heart cells give the vital organ its necessary stiffness during development.

Read the full story on the Penn Engineering blog.

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Macrophages Engineered Against Cancer Cells

macrophages Discher
Dennis Discher, Ph.D.

Dennis E. Discher, Ph.D., Robert D. Bent Professor in the Department of Chemical and Biomolecular Engineering and a secondary faculty member in the Department of Bioengineering, was the lead author on a recent study that showed that engineered macrophages (a type of immune cell) could be injected into mice, circulate through their bodies, and invade solid tumors in the mice, engulfing human cancers cells in the tumors.

According to Cory Alvey, a graduate student in pharmacology who works in Professor Discher’s lab and the first author on the paper, said, “Combined with cancer-specific targeting antibodies, these engineered macrophages swarm into solid tumors and rapidly drive regression of human tumors without any measurable toxicity.”

Read more here.