Part of Dennis Plenker鈥檚 daily job, as a 黑料吃瓜资源 (CSHL) research investigator, is growing cancer. And a variety of different ones, too.
Depending on the day and the project, different tumors may flourish. They might be aggressive breast cancers. They might be glioblastomas, one of the deadliest brain tumors that rob patients of their ability to speak or read as they crowd out normal cells. Or they might be pancreatic cancers, the fast and vicious slayers that can overtake a healthy person within weeks or even days.
These tiny tumor chunks are transparent and bland鈥攖hey look like little droplets of hair gel that accidentally plopped into a plastic dish and took hold. But their unassuming appearance is deceptive. If they were still in the human bodies from which they came, they would be growing rapidly, sucking up nutrients, and dodging the immune system defenses. But in Plenker鈥檚 hands鈥攐r rather in CSHL鈥檚 unique facility鈥攖hese notorious killers don鈥檛 kill anyone. Instead, scientists let them grow in order to devise the most potent ways to kill them.
These tumor chunks are called organoids. They are three-dimensional assemblages of malignant growths used to study cancer behavior and vulnerability to chemotherapy and the so-called 鈥渢argeted drugs鈥濃�攖he next-generation therapies. Scientists used to study tumors at a single-cell level, but because tumors grow as cell clusters in the body, it proved to be inefficient. The three-dimensional structure makes a difference. For example, chemo might destroy the tumor鈥檚 outer cell layer, but the inner layers can develop resistance, so where single cells may die, a 3D mass will bounce back. Organoids provide a way to study these mechanisms of drug resistance that are not well understood. They can reveal how normal tissues turn malignant and where the cellular machinery goes off-track to allow that to happen.
As their name suggests, organoids are scientists鈥� windows into organs, whether healthy or stricken with disease. You need to know your enemy to beat it, Plenker says, and cancer organoids offer that opportunity. Taken from patients currently undergoing cancer treatments, these tumor chunks will reveal the Achilles鈥� heels of these cancers so scientists can devise personalized treatments. 鈥淥rganoids are essentially patients in a dish,鈥� Plenker says. Only unlike real patients, the organoids can be subjected to all sorts of harsh experiments to zero in on the precise chemo cocktails that will destroy them the best. And they will likely provide a more realistic scenario than drug tests in mice or rats, as animal models aren鈥檛 perfect proxies for humans.
Organoids are essentially patients in a dish. Unlike real patients, organoids can be subjected to all sorts of harsh experiments.鈥�
Dennis Plenker, Ph.D.
The way that cancer proliferates in the body is hard to reproduce in the lab. Stem-cell research made it possible. After scientists spent a decade understanding how various cells multiply and differentiate into other cell types based on molecular cues and nourishment, they were able to make cells grow and fuse into tissues. To stick together like bricks in a nicely laid wall, cells need a biological scaffold. Scientists call this scaffold the extracellular matrix or ECM, which in the body is made from a protein called collagen and other materials. Today, the same collagen scaffolds can be mimicked with a gooey substance called Matrigel, which allows cells to take root and begin to multiply.
Some tissue types were easy to grow鈥擟olumbia University scientists as early as 2010. Others, like kidney cells, were trickier. They would grow into immature tissues incapable of performing their job of cleaning and filtering blood. It took scientists time to realize that these cells needed more than scaffolding and food鈥攖hey needed to 鈥渇eel at home,鈥� or be in their natural habitat. Kidney cells needed the feeling of liquid being washed over them, a Harvard University group found, when they first managed to in 2018.
Cancers have their own growth requirements. In the body, they manage to co-opt their needed resources. But keeping them happy in a dish means catering to their dietary preferences. Different cancers need different types of molecular chow鈥攇rowth factors, hormones, oxygen and pH levels, and other nutrients. Pancreatic adenocarcinoma with poor nutrients. Glioblastomas . These nutrients are delivered to organoids via a specific solution called growth medium, which lab personnel regularly dole out into the dishes.
Plenker is charged with keeping this murderous menagerie alive and well. He is the one who designs the cancers鈥� dietary menu, a specific recipe for each type. And while his official title is organoid facility manager and research investigator who works with David Tuveson, director of the CSHL鈥檚 Cancer Center, he is essentially a cancer custodian. He curates a unique collection that aims to change the paradigm of cancer treatment.
Perfecting chemotherapy recipes
Plenker鈥檚 research area is pancreatic cancer鈥攐ne of the most notorious killers known. Often diagnosed late and resistant to treatment, it is essentially a death sentence鈥攐nly 8 to 10% of patients remain alive five years after diagnosis. The chemo drugs used to treat it haven鈥檛 changed in 40 years, Plenker says. In the past decade, physicians tried combining multiple drugs together with relative success. Identifying winning combos can save lives, or at least prolong them鈥攁nd that鈥檚 what the organoids will help clinicians do better.
In a groundbreaking clinical trial called PASS-01 (for Pancreatic Adenocarcinoma Signature Stratification for Treatment), Plenker鈥檚 team collaborates with other American and Canadian colleagues to identify the most effective chemo cocktails and to understand the individual patients鈥� tumor behaviors. Their results could lead to more personalized treatments.
Scientists know the same cancer types can behave differently in different patients. Typically, all malignancies have a 鈥渄river mutation鈥� in a certain gene that triggers the cancer. But tumors also often have 鈥減assenger mutations鈥� that happen in nearby genes. These neighboring mutant genes generate various proteins, which may interfere with treatment. Or not. Scientists call these mutated gene combinations tumor mutational signatures, which can vary from one patient to the next. With some cancers, doctors already know what mutational signatures they may have, but with pancreatic cancer they don鈥檛 have good tell-tale signs, or biomarkers. 鈥淭here aren鈥檛 many biomarkers to help clinicians decide which chemo may be better for which patient,鈥� explains oncologist Grainne O鈥橩ane, who treats pancreatic cancer patients at the Princess Margaret Hospital in Toronto, Canada.
That鈥檚 the reason O鈥橩ane participates in the PASS-01 trial鈥攊t will give doctors a better view into the exact specifics of their patients鈥� malignancies. As they take their patients鈥� biopsies, they send little cancer snippets to the CSHL facility to be grown into organoids. There, the organoids will be subjected to chemo cocktails of various combinations to design more personalized regiments for them.
The hospital treats all patients with the so-called standard of care chemotherapy, which is more of a one-size-fits-all approach. Some patients will respond to it but others won鈥檛, so the goal is to define the second line of chemo defense in a more personalized fashion. 鈥淭hat鈥檚 where the biopsies we send to Tuveson鈥檚 lab might be useful,鈥� O鈥橩ane says. 鈥淭hey can help us find something to benefit patients after the first line of chemo stopped working.鈥�
There aren鈥檛 many biomarkers to help clinicians decide which chemo may be better for which patient.鈥�
Grainne O鈥橩ane, M.D.
Scientists can try all kinds of treatments on the tumorous organoids, which they can鈥檛 do in living people. 鈥淵ou can treat 100 organoids with 100 different compounds and see which one works, or which compound does a good job and which ones don鈥檛 work at all,鈥� Plenker says. That would also allow scientists to define the precise amount of chemo better, so doctors wouldn鈥檛 have to over-treat patients with harsh drugs that create sickening side effects. Ultimately, organoids should take a lot of guesswork out of the treatment process.
With about 150 patients鈥� adenocarcinomas already collected, the team hopes to come up with some answers. O鈥橩ane says her team already has three patients for which they were able to design the more personalized second line of defense chemo, based on what their organoids revealed. They haven鈥檛 yet tried it, because the trial has only started recently, but this would be the next step. 鈥淏eing able to piece all this information together in real-time as patients are moving through their therapies can really improve the outcomes,鈥� O鈥橩ane says. And while they may not be able to save all of those who graciously donated their biopsy snippets to science, it will help build better treatments in the future. 鈥淓ven if we won鈥檛 be able to help these specific patients we鈥檙e hoping to use this info in future clinical trials,鈥� O鈥橩ane says.
Replicating biology in a dish
Organoids can also help scientists understand how cancer develops. This is particularly true for breast cancers, says Camila dos Santos, associate professor and a member of the CSHL Cancer Center. She studies the inner life of human mammary glands and tissue, more commonly referred to as breasts, and is also part of the cancer custodian crew. The hormonal changes that women go through during pregnancy subsequently modify breast cancer risk, sometimes lowering it and sometimes increasing it鈥攁 complex interplay of the body鈥檚 chemicals.
CSHL Assistant Professor Camila dos Santos discusses how her lab uses organoids to study how pregnancy reduces breast cancer risk in this episode of CSHL鈥檚 LIVE At the Lab.
鈥淲e know that women who get pregnant for the first time before they turn 25 years old, have a 30% decrease in breast cancer incidence later in life,鈥� dos Santos says. 鈥淲hen they turn 60 or 70, 30% of them will not develop cancer.鈥� On the contrary, those who are pregnant past 38 have a 30 to 50% increase in developing aggressive breast cancer types. Clearly, some molecular switches are involved, but they are very hard to study within the body. That鈥檚 where organoids can provide a window into the surreptitious process.
Using breast organoids, scientists can model the complex life of mammary glands at various stages of a woman鈥檚 life. And while most women wouldn鈥檛 want their breasts poked and pierced when they are pregnant or breastfeeding, many donate their tissues after breast reduction surgery or prophylactic mastectomy due to high-risk mutations like the BRCA gene. That鈥檚 where organoids shine because scientists can not only grow them, but also give them pregnancy hormonal cues, which make cells generate milk or stop lactating, to study the complex cellular interactions that take place in real life.
There鈥檚 a lot to study. At birth, mammary glands are similar in both genders鈥攋ust little patches of the mammary epithelium tissue. But when puberty hits, the female glands fill up with the so-called mammary tree鈥攁 system of ducts for future milk production, which fully 鈥渂looms鈥� in pregnancy. 鈥淲hen a woman becomes pregnant, the duct tree expands, growing two types of cells鈥攍uminal and myoepithelial ones,鈥� explains Zuzana Koledova, assistant professor of Masaryk University in the Czech Republic. She also uses organoids in her work. When babies are born, the luminal cells, which line the inside of the ducts, produce the proteins that comprise milk. The myoepithelial cells reside outside the ducts and work as muscles that squeeze the ducts to push milk out. Dos Santos likens this pregnancy mammary gland growth to the changes of the seasons. The images of sprouting ducts look like blossoming trees in the spring while later they shrivel like plants do in the fall.
The body governs these processes via the molecular machinery of hormones, which stimulate breast cell growth during pregnancy, and later cause them to die out. The two pregnancy-related hormones, prolactin and oxytocin, are responsible for milk production. Prolactin induces the luminal cells to make milk while oxytocin makes the myoepithelial cells contract. Once the baby is weaned, the levels of these hormones drop, causing cells to shrink back to their non-pregnant state.
With organoids, scientists can observe these cellular dynamics at work. Koledova鈥檚 team had watched breast organoids secrete milk based on biological cues. They even recorded movies of cells pumping tiny milk droplets in the dish that they were growing in. Using tiny snippets of donated breast tissue, the team grew the organoids and then added the two pregnancy hormones into the mix, explains Jakub Sumbal, a mammary gland researcher in Koledova鈥檚 group. As they began to secret proteins that compose milk, the organoids, which looked like little domes inside the dish, changed from translucent to opaque. 鈥淎t first, you can see through them, but then as they produce these proteins, they kind of darken,鈥� Sumbal says. 鈥淎nd you can see them pushing out these little droplets.鈥�
Dos Santos鈥檚 team outlined molecular changes that follow such dish-based hormonal cues in . In response to hormonal messages, cells produce proteins, which they display on their surfaces, like status symbols. During pregnancy the burgeoning cells prepping for milk production display the 鈥減rotein flags鈥� that make them look important so they receive additional nourishment. When it鈥檚 time to die, they commit a type of cellular suicide. They signal bypassing macrophages鈥攖he immune system鈥檚 cleanup crew鈥攖o devour them. 鈥淭hey essentially say 鈥榗ome eat me!鈥� to the macrophages,鈥� dos Santos says. 鈥淏ecause I鈥檓 no longer needed.鈥�
Sometimes cancer cells can recruit specific types of immune cells to protect them.鈥�
Camila dos Santos, Ph.D.
The ability to mimic these processes in a dish allows scientists to study the molecular switches that trigger breast cancer development鈥攐r minimize it. Scientists know that cancerous cells can hide from the immune system and even co-opt it into protecting themselves. They do it by displaying their own 鈥渄o not eat me鈥� protein flags on the surface to avoid destruction. 鈥淪ometimes cancer cells can recruit specific types of immune cells to protect them,鈥� dos Santos says. 鈥淭hey can not only say 鈥榙o not eat me,鈥� but say 鈥榗ome hang out with me鈥� to the macrophages, and the macrophages will send suppressive signals to the B-cells or T-cells, the body鈥檚 defenders.鈥� It is as if the cancer requests protection鈥攁 crew of guardians around it to defend against other cells that would otherwise wipe it out.
Scientists can鈥檛 dive inside the body to peek at these interactions, but they now can watch these stealth battles unfolding in a dish. 鈥淩ight now we are looking at the proteins that are secreted by the organoids鈥攖he proteins that go on the surface of the organoids鈥� cells and what they would communicate to the immune system,鈥� dos Santos says. 鈥淓ven when there鈥檚 no immune system surrounding them, they would still be doing that.鈥� There鈥檚 a way to mimic the immune system, too. Scientists can add B-cells, T-cells, macrophages, and other players into the growth medium and watch the full-blown cellular warfare in action. 鈥淭hat鈥檚 the next step in our research,鈥� dos Santos says.
Cancer patients would no longer have to undergo chemotherapy by trial and error.鈥�
Understanding what hormonal fluxes trigger breast cancer, and how it recruits other cells for safekeeping, can give scientists ideas for pharmaceutical intervention. 鈥淲e can find drugs that pharmacologically turn off the switches that trigger cancer or interrupt its signaling for protection,鈥� dos Santos says. 鈥淭hat opens novel ways to treat people.鈥�
Tumor molecular mugshots
Can organoid research lead to a new standard of care for cancer patients? That鈥檚 the ultimate goal, researchers say. That鈥檚 why Plenker works at keeping his collection of cancer glops alive and well and thriving鈥攈e calls it a living biobank. He is also developing protocols that would allow commercial companies to grow organoids the same way chemical industries make reagents or mice suppliers grow rodents for research. A benefit of organoid experiments is they don鈥檛 involve animals at all.
. . . once enough data is gathered about the tumors鈥� mutational signatures, scientists may create a database of tumor ‘mugshots’ matching them to the chemo cocktails that beat them best.鈥�
Dennis Plenker, Ph.D.
Hospitals may one day start growing organoids from their patients鈥� biopsies to design and test personalized chemo cocktails for them. Once science crosses over to that reality, the entire treatment paradigm will change. Cancer patients won鈥檛 have to undergo chemotherapy by trial and error. Instead, their cancer organoids will be subjected to this process鈥攖ested with a gamut of drug combinations to find the winning one to use in the actual treatment. Plenker notes that once enough data is gathered about the tumors鈥� mutational signatures, scientists may create a database of tumor 鈥渕ugshots鈥� matching them to the chemo cocktails that beat them best. And then just sequencing a biopsy sample would immediately inform oncologists what drug combo the patient needs. 鈥淲e may be about 10 years away from that,鈥� Plenker says, but for now there鈥檚 a lot more research to do. And a lot more cancers to grow.
Written by: Lina Zeldovich, Science Writer | [email protected] | 516-367-8455