Posts

cancer cell

Muller Fabbri, M.D., Ph.D.: The microRNA journey and the future of cancer therapy

cancer cell

Children’s National Hospital welcomes Muller Fabbri, M.D. Ph.D., as associate director for the Center for Cancer and Immunology Research at the Children’s National Research Institute. In this role, he will build and lead the Cancer Biology Program while developing and conducting basic and translational research. Dr. Fabbri will also develop multidisciplinary research projects with various clinical divisions, including oncology, blood and marrow transplantation, pathology and hematology.

Dr. Fabbri shares his journey working with microRNAs, how his work is advancing the field and his vision for the Center for Cancer and Immunology Research at Children’s National.

Q: You have been working with microRNAs for quite some time. How are you exploring the role of microRNAs in cancer?

A: It was well established within the scientific community that a gene, which is a piece of DNA, becomes a piece of RNA and then becomes a protein. This thought process was pretty much a one-way flow of information that we had, going from DNA to protein as part of a cell function. But, almost 30 years ago, it was discovered that this is not entirely true because what happens is that some of these genes that are transcribed into RNA do not become a protein. Instead, they stay as RNA. Some of these RNAs are tiny and have short sequences, which is why they are called microRNAs.

I work primarily on microRNAs and non-coding RNAs and my research studies focus on the role that microRNAs play in cancer. I can take a cancer cell and a healthy cell and observe how these microRNAs are expressed in the two different cell populations. In this way, the microRNAs expressed in cancer cells are profoundly different from the microRNAs expressed in healthy cells.

We conducted a series of studies to observe what happens to a cancer cell if we restore normal levels of certain microRNAs like the ones you would see in a normal cell. We discovered that by restoring some of these microRNAs levels it led to the death of the cancer cells, suggesting that this approach may be used as a cancer treatment. This is one of the research areas that I will further develop at Children’s National as I seek to understand the mechanisms that control microRNA expression and subsequently affect cancer cell proliferation. With this information, we can target these mechanisms and create drugs that interfere with this function and, hopefully, stop cancer cell growth.

Q: Can you tell us about that eureka moment with your best friend during a lunch break?

A: This was a bit of a crazy idea. I will never forget. I shared a theory during a lunch break with a friend. I dared to ask, what if microRNAs worked like hormones? MicroRNAs can be detected in the blood of patients with cancer, and they can be transferred from one cell to another inside of little vesicles called exosomes. If you think about it, I further asked, what other molecules in our body behave like that — i.e. are secreted, circulate in the blood and then transferred to a target cell? My friend replied, “well, those would be hormones.” To which, I added, yes, exactly! Then, why do we not think of RNAs as hormones? And I quote him now, “you are crazy, but if it works it is huge.”

I felt that I had some validation from my best friend, so I decided to invest in this crazy idea, carving extra time on the side while working on my “safe” projects. It was one of those rare cases in science, where in a little over a year, we showed for the first time that microRNAs do not only work the traditional way, but they can also work as hormones. They do have a receptor protein to attach to, and by binding to this protein, they trigger a response in a cell that can be pro-tumoral or anti-tumoral.

Even today, if you open a textbook of endocrinology, under the chapter of hormones, it mentions that there are only two categories, proteins and lipids. Well, it turns out there is a third category, which is nucleic acids because of RNAs.

Q: You mentioned other research areas of interest as it relates to cancer cell biology. What are they?

A: The other line of research that I am developing stems from the original observation that I made in 2012. Cancer cells release tiny vesicles that I like to compare to envelopes containing a written message — the RNA and microRNA. These vesicles released in the surrounding environment contain a message captured by immune cells, known as macrophages. Macrophages act as scavengers in our bodies. In cancer, macrophages are supposed to digest and destroy the cancer cell. However, it turns out that they also have the proper receptor to receive and read the message enclosed in the vesicles. Then, something shocking happens. The macrophage stops fighting the cancer cell and starts producing proteins called cytokines that promote cancer growth. This finding means that we are 180 degrees apart from what we thought at the beginning. A lot of macrophages in the cancer are good news for the patient because they are supposed to kill cancer cells, but because of this mechanism, a lot of macrophages can be bad news since they can also help the cancer cell grow.

My contribution to this discovery was to investigate how the macrophage response is mediated. I discovered that macrophages operate, at least in part, by expressing receptors that bind to microRNAs released by the cancer cell, thereby favoring cancer growth. In the pediatric cancer field we discovered that because of this microRNA–receptor interaction, the pediatric tumor neuroblastoma becomes resistant to chemotherapy. Therefore, one of the strategies we are working on now is to interfere or impair these negative communications between the cancer cell and immune cell. We want to disrupt these communications so the macrophage cannot read the message from the cancer cell anymore and instead keeps doing its job to fight the cancer. We hope that we can leverage this approach to develop novel cancer treatments or create strategies that improves immune cell function in the presence of the patient’s current therapy to enhance an anti-cancer treatment response.

Q: What is your vision for the Center of Cancer and Immunology Research?

A: I am very excited about what I saw at Children’s NationalI was delighted to talk to many faculty members, and I recognized the immense talent within the Center. I would like to help elevate and enhance the cancer biology program focused on solid tumors, and augment the work being done in this space by the cell therapy program. The clinicians are clearly eager to collaborate with the basic scientists including the sharing of samples and ideas, which is not typical of many scientific environments. My other goal is to ensure that the Cancer Biology Program plays a central role in acquiring an NCI-Designated Cancer Center recognition often given to institutions that stand out in scientific leadership and clinical research. Finally, I want to create the first national center that develops extracellular vesicles as an innovative treatment strategy for cancer. Importantly, I think that we have all the resources and connections at Children’s National that are necessary to realize this vision!

 

Karun-Sharma-and-kids-MR-HIFU

FDA approves MR-HIFU system to treat osteoid osteoma

Karun-Sharma-and-kids-MR-HIFU

“This FDA approval encourages and further motivates our focused ultrasound program to continue to develop and expand clinical applications of MR-HIFU in the pediatric population,”  said Karun Sharma, M.D., Ph.D.

After garnering successful clinical trial results at Children’s National Hospital, the United States Food and Drug Administration (FDA) recently announced the approval of Profound Medical’s Sonalleve MR-guided High Intensity Focused Ultrasound (MR-HIFU) system for the treatment of osteoid osteoma (OO) in the extremities. OO is a benign, but painful bone tumor that occurs most commonly in children and young adults. This marks the first focused ultrasound regulatory approval that will directly impact pediatric patients and it is the sixth indication to earn approval in the United States.

Nine patients were treated in a pilot trial designed to evaluate the safety and feasibility of MR-HIFU ablation treatment in patients with painful OO. The procedure was performed without any technical difficulties or serious adverse events in all nine patients, and resulted in complete pain relief with no further pain medication usage in eight out of nine patients.

“This FDA approval encourages and further motivates our focused ultrasound program to continue to develop and expand clinical applications of MR-HIFU in the pediatric population,” said Karun Sharma, M.D., Ph.D., director of Interventional Radiology and associate director of clinical translation at the Sheikh Zayed Institute for Pediatric Surgical Innovation (SZI) at Children’s National. “This completely non-invasive and radiation-free aspects of this therapy are especially relevant for growing children.”

Researchers at Children’s National have moved beyond OO are also evaluating MR-HIFU treatment for patients with relapsed and refractory bone and soft tissue tumors. “This is especially important as these patients don’t have any other good treatment options,” said Dr. Sharma. “For these tumors, we are using not only thermal ablation, but also other modes and biomechanisms of focused ultrasound such as mild hyperthermia to facilitate targeted, enhanced drug delivery and histotripsy (i.e., mechanical tissue fractionation) to enhance cancer immunotherapy. We also hope to move into MR-HIFU brain application in pediatrics.”

At Children’s National, a multidisciplinary team of physicians and scientists use MR-HIFU to focus an ultrasound beam into lesions to heat and destroy the tissue in that region, with no incisions at all. In 2015, Children’s National doctors became the first in the U.S. to use MR-HIFU to treat pediatric osteoid osteoma. The trial, led by Dr. Sharma, demonstrated early success in establishing the safety and feasibility of noninvasive MR-HIFU in children as an alternative to the current, more invasive approaches to treat these tumors. Since then, the Children’s National team has built an active clinical trials program and become a leader in translation of focused ultrasound for the treatment of relapsed pediatric solid tumors.

2019 at a glance: Oncology at Children’s National

Oncology at Children's National
ID-KD vaccine induced T-cell cytotoxicity

Fighting lethal cancer with a one-two punch

The immune system is the ultimate yin and yang, explains Anthony D. Sandler, M.D., senior vice president and surgeon-in-chief of the Joseph E. Robert Jr. Center for Surgical Care at Children’s National in Washington, D.C. With an ineffective immune system, infections such as the flu or diarrheal illness can run unchecked, causing devastating destruction. But on the other hand, excess immune activity leads to autoimmune diseases, such as lupus or multiple sclerosis. Thus, the immune system has “checks and balances” to stay controlled.

Cancer takes advantage of “the checks and balances,” harnessing the natural brakes that the immune system puts in place to avoid overactivity. As the cancer advances, molecular signals from tumor cells themselves turn on these natural checkpoints, allowing cancers to evade immune attack.

Several years ago, a breakthrough in pharmaceutical science led to a new class of drugs called checkpoint inhibitors. These medicines take those proverbial brakes off the immune system, allowing it to vigorously attack malignancies. However, Dr. Sandler says, these drugs have not worked uniformly and in some cancers, they barely work at all against the cancer.

One of these non-responders is high risk neuroblastoma, a common solid tumor found outside the skull in children. About 800 U.S. children are diagnosed with this cancer every year. And kids who have the high-risk form of neuroblastoma have poor prognoses, regardless of which treatments doctors use.

However, new research could lead to promising ways to fight high-risk neuroblastoma by enabling the immune system to recognize these tumors and spark an immune response. Dr. Sandler and colleagues recently reported on these results in the Jan. 29, 2018, PLOS Medicine using an experimental model of the disease.

The researchers created this model by injecting the preclinical models with cancer cells from an experimental version of neuroblastoma. The researchers then waited several days for the tumors to grow. Samples of these tumors showed that they expressed a protein on their cell surfaces known as PD-L1, a protein that is also expressed in many other types of human cancers to evade immune system detection.

To thwart this protective feature, the researchers made a cancer vaccine by removing cells from the experimental model’s tumors and selectively turning off a gene known as Id2. Then, they irradiated them, a treatment that made these cells visible to the immune system but blocked the cells from dividing to avoid new tumors from developing.

They delivered these cells back to the experimental models, along with two different checkpoint inhibitor drugs – antibodies for proteins known as CLTA-4 and PD-L1 – over the course of three treatments, delivered every three days. Although most checkpoint inhibitors are administered over months to years, this treatment was short-term for the experimental models, Dr. Sandler explains. The preclinical models were completely finished with cancer treatment after just three doses.

Over the next few weeks, the researchers witnessed an astounding turnaround: While experimental models that hadn’t received any treatment uniformly died within 20 days, those that received the combined vaccine and checkpoint inhibitors were all cured of their disease. Furthermore, when the researchers challenged these preclinical models with new cancer cells six months later, no new tumors developed. In essence, Dr. Sandler says, the preclinical models had become immune to neuroblastoma.

Further studies on human patient tumors suggest that this could prove to be a promising treatment for children with high-risk neuroblastoma. The patient samples examined show that while tumors with a low risk profile are typically infiltrated with numerous immune cells, tumors that are high-risk are generally barren of immune cells. That means they’re unlikely to respond to checkpoint inhibiting drugs alone, which require a significant immune presence in the tumor microenvironment. However, Dr. Sandler says, activating an immune response with a custom-made vaccine from tumor cells could spur the immune response necessary to make these stubborn cancers respond to checkpoint inhibitors.

Dr. Sandler cautions that the exact vaccine treatment used in the study won’t be feasible for people. The protocol to make the tumor cells immunogenic is cumbersome and may not be applicable to gene targeting in human patients. However, he and his team are currently working on developing more feasible methods for crafting cancer vaccines for kids. They also have discovered a new immune checkpoint molecule that could make this approach even more effective.

“By letting immune cells do all the work we may eventually be able to provide hope for patients where there was little before,” Dr. Sandler says.

In addition to Dr. Sandler, study co-authors include Priya Srinivasan, Xiaofang Wu, Mousumi Basu and Christopher Rossi, all of the Joseph E. Robert Jr. Center for Surgical Care and The Sheikh Zayed Institute for Pediatric Surgical Innovation (SZI), at Children’s National in Washington, D.C.

Financial support for research described in this post was provided by the EVAN Foundation, the Catherine Blair foundation, the Michael Sandler Research Fund and SZI.

ID-KD vaccine induced T-cell cytotoxicity

Mechanism of Id2kd Neuro2a vaccination combined with α-CTLA-4 and α-PD-L1 immunotherapy in a neuroblastoma model. During a vaccine priming phase, CTLA-4 blockade enhances activation and proliferation of T-cells that express programmed cell death 1 (PD1) and migrate to the tumor. Programmed cell death-ligand 1 (PD-L1) is up-regulated on the tumor cells, inducing adaptive resistance. Blocking PD-L1 allows for enhanced cytotoxic effector function of the CD8+ tumor-infiltrating lymphocytes. Artist: Olivia Abbate

Anthony Sandler

Treatment of neuroblastoma with immunotherapy and vaccine combination shows promise

Anthony Sandler

“Treatment options like these that help the body use its own immune system to fight off cancer are incredibly promising, and we look forward to continuing this work to understand how we can best help our patients and their families,” said Anthony Sandler, M.D.

Despite being the most common extracranial solid tumor found in children and having multiple modes of therapy, neuroblastoma continues to carry a poor prognosis. However, a recent cutting-edge pre-clinical study, PD-L1 checkpoint inhibition and anti-CTLA-4 whole tumor cell vaccination counter adaptive immune resistance: A mouse neuroblastoma model that mimics human disease, published in PLOS Medicine shows the first signs of success in treating high-risk neuroblastoma, a promising step not only for neuroblastoma patients, but potentially for other types of cancer and solid tumors as well. While the research was conducted on mouse models and is in the early stages, the lead author of the study, Anthony Sandler, M.D., senior vice president and surgeon-in-chief of the Joseph E. Robert, Jr., Center for Surgical Care at Children’s National, believes these findings are an encouraging development for the field.

The treatment method combines a novel personalized vaccine and a combination of drugs that target checkpoint inhibitors enabling the immune system to identify and kill cancer cells. When these checkpoints are blocked, it’s similar to taking the brakes off the immune system so that the body’s T cells can be primed by the vaccine, identify the tumor and allow for targeted tumor cell killing. The vaccine then brings in reinforcements to double down on the attack, helping to eradicate the tumor. The vaccine could also be used as a way to prevent recurrence of disease. After a patient has received the vaccine, the T cells would live in the body, remembering the tumor cells, and attack reemerging cancer in a similar way that a flu vaccine helps fight off the flu virus.

“Treatment options like these that help the body use its own immune system to fight off cancer are incredibly promising, and we look forward to continuing this work to understand how we can best help our patients and their families,” said Dr. Sandler.