Author: Johanna Lee

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Autophagy: The Poem

Roberta A. Gottlieb, MD, is the Director of Molecular Cardiobiology at Cedar-Sinai, a nonprofit academic healthcare organization. She is interested in the role of autophagy in myocardial ischemia, a kind of heart disease in which blood flow to the heart is blocked. (Studies have shown that autophagy is upregulated during myocardial ischemia, but why this happens is not entirely clear.) Her ultimate goal is to understand and mitigate ischemic injury, with the hope of developing therapeutics for humans.

And—she’s a poet. Continue reading →

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Using Environmental DNA to Find Sharks

Sharks are often known as one of the fiercest predators in the ocean. Yet they are also one of the most threatened marine species—largely because they are hunted by humans for their highly valuable fins. How do we know they are being threatened? Continue reading →

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High-Throughput Drug Screening Using 3D Cell Cultures

For a long time, the drug industry has relied on flat 2D cell cultures grown on a plate to screen for potential drugs. However, 2D models do not accurately reflect the native environment of cells in vivo. 3D cell cultures, on the other hand, better represent the numerous cell-cell and cell-matrix interactions and hypoxic conditions that have a profound effect on the behavior of cells. In a 2018 study published in Oncogene, Kota et al. developed a high-throughput 3D spheroid-based screening assay to identify drug candidates that target RAS proteins.

RAS proteins are GTPases that transmit extracellular signals into cellular signaling pathways, which could activate cell proliferation, differentiation and survival mechanisms. Oncogene mutation in the three human RAS genes (HRAS, NRAS and KRAS) are found in 30% of all cancers, making RAS proteins the most common oncogene. In fact, mutations in KRAS are found in >90% of pancreatic cancers. Despite the prevalence of RAS mutations, targeting RAS proteins with drugs is extremely challenging due to the complex nature of the protein.

The authors in this study wanted to test a new approach using a 3D spheroid-based screening assay to find drugs that target RAS proteins. They first harvested 2D monolayer cultures of pancreatic epithelial tumor cells that express either wild-type KRAS or mutant oncogenic KRAS, and tested their ability to form 3D spheroids. They confirmed spheroid growth using the CellTiter-Glo® 3D Cell Viability Assay with linearity of detection in the range of 1,000–10,000 cells seeded.

The 3D spheroids were then treated with a library of 1,280 known drugs. From the high-throughput screen, they identified one compound with the greatest selective inhibition against oncogenic KRAS. The compound is called Proscillaridin A, a cardiac glycoside that is known for treating congestive heart failure and cardiac arrhythmia. In 3D spheroids, Proscillardin A inhibited oncogenic KRAS at a >90% inhibition rate, with <10% inhibition of wild-type KRAS. In 2D cultures, however, there was no selective inhibition of oncogenic KRAS (inhibition rates for both oncogenic and wild-type KRAS were about 50%). This means that Proscillaridin A would not have been identified as a candidate if the screen was done using only 2D cultures.

Next, the authors wanted to determine how Proscillaridin A impacts tumor cell viability. Could it induce apoptosis in tumor cells? To test this, they used the RealTime-Glo™ Annexin V Apoptosis Assay. This bioluminescent assay is able to detect apoptosis in real time, based on the exposure of phosphatidylserine on the outer leaflet of the cell membrane when apoptosis occurs. Using this assay, they found that Proscillaridin A induced apoptosis at earlier time points and higher rates in 3D spheroids expressing oncogenic KRAS compared with wild-type KRAS. In 2D cultures, there was no difference in the rate of apoptosis.

This study shows that high-throughput screening in 3D spheroids can identify potential drugs that would not have been discovered in a 2D format. This provides hope for finding drugs against difficult target proteins such as RAS.

Reference: Kota S., et al. (2018) A novel three-dimensional high-throughput screening approach identifies inducers of a mutant KRAS selective lethal phenotype. Oncogene. Epub ahead of print.

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Wonders of the Conscious and Unconscious Mind—What I Learned from the International Forum on Consciousness

When Heather Berlin was 5 years old, she realized that, at some point in the future, she was going to die. This disturbed her so much that she couldn’t sleep all night. The next morning, she asked her father where she could store all her thoughts so they could live on after she died. There’s no way to do that, said her physician father. “What can I do to make this happen?” she asked. “Maybe become a psychiatrist?” said her dad. Decades later, she became an Assistant Professor of Psychiatry at Icahn School of Medicine at Mount Sinai. Her research focuses on interactions of the brain and mind, with the goal of treating and preventing psychiatric and neurological disorders.

Dr. Heather Berlin told this story at the International Forum on Consciousness held at the BioPharmaceutical Technology Center Institute in Madison, Wisconsin last week. This annual forum gathers scientists from around the world, all interested in understanding how our conscious and unconscious minds work. This year, the forum focused on the newest research and technology for detecting and measuring consciousness. As someone with limited knowledge in this field, my mind was blown by how much researchers have learned so far about consciousness. (No, we can’t store our thoughts in a box…yet.) Here are a few takeaways: Continue reading →

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20 Years of Human Embryonic Stem Cells

Dr. David Russell presenting at the 13th Wisconsin Stem Cell Symposium. The session was moderated by Dr. James Thomson.

“20 years ago, when I first heard about the creation of human embryonic stem cells, I knew that this was the future. I immediately requested the cells from Dr. Thomson and dropped almost everything else we were doing in our lab. It has been my focus to this day.” The person presenting is Dr. David Russell, a professor at the University of Washington. He is just one of the hundreds of researchers gathered at the BioPharmaceutical Technology Center Institute (a nonprofit supported by Promega) in Madison, Wisconsin for the 13th Annual Wisconsin Stem Cell Symposium that happened this week. This year, it’s not just a symposium, but also a celebration—it’s the 20-year anniversary of the first-ever isolation and culture of human embryonic stem (ES) cells.

In 1998, Dr. James Thomson, at the University of Wisconsin-Madison, created the first ES-cell line using donated (unused) embryos from a fertility clinic. The study sent a shockwave through the scientific community and general public. We now had the technology to grow human pluripotent ES cells—with the potential to develop into every cell type in the human body—in a dish! Thomson quickly became a celebrity scientist. (Thomson’s headshot was on the cover of the August 20, 2001 issue of Time Magazine, next to big text that read: “The Man Who Brought You Stem Cells”.)

However, not all were excited about the news. Backlash from conservative communities, who opposed the use of human embryos, resulted in a temporary ban on developing new ES cell lines with government funding. Nonetheless, the ban did not deter researchers from studying ES cells using private or state funding. By 2001, human ES cells have been successfully derived into neural, cardiac, hematopoietic, endothelial, and insulin-producing cells. In 2010, the first in-human clinical trial was initiated; which used human ES cell-derived materials to treat spinal cord injury.

2006 marked another milestone in stem cell research: the discovery of induced pluripotent stem (iPS) cells. Dr. Shinya Yamanaka at Kyoto University successfully reprogrammed adult fibroblasts (common cells in connective tissue that form the extracellular matrix and collagen) to revert back into an embryonic-like pluripotent state—simply by expressing four specific genes. He named these reprogrammed cells “induced pluripotent stem cells” or iPS cells. A year later, human iPS cells were made in a similar fashion by both Thomson and Yamanaka. Yamanaka later received the 2012 Nobel Prize (some argue that Thomson deserved to share the prize).

Photo credit: 123rf stock photos.

The ability to reprogram adult cells back into a pluripotent state suggested we could create an unlimited supply of pluripotent cells that genetically matched a specific individual—without the ethical baggage of using human embryos. This meant, in theory, you could take fibroblasts from a patient with a neurological disorder, such as Parkinson’s disease, revert the fibroblasts into iPS cells, edit the “faulty genes” in those cells, then redifferentiate the healthy iPS cells into neural stem cells that can be introduced back into the same patient to produce healthy neurons. Of course, this is easier said than done. The technical difficulties and high cost of generating and editing iPS cells from individual patients have complicated the development of iPS-based treatments. Currently, there is only one human clinical trial using cells derived from iPS cells, which treats macular degeneration (an incurable eye disease that leads to blindness).

Despite the emergence of iPS cells, ES cells have continued to dominate in the clinical realm. To this date, there are 18 clinical trials using ES cells to treat various disorders, including macular degeneration, Parkinson’s disease, spinal cord injury, heart disease and diabetes. The future is bright, but there is still one major problem in ES cell-based therapies. Because ES cell treatments use donor cells from other healthy individuals—not the patients’ own cells—there is a high risk of immune rejection. But no fear, scientists have a plan.

In 2017, Dr. David Russell (mentioned in the beginning of this blog) re-engineered human ES cells to remove specific proteins—human leukocyte antigens (HLA)—from the cell surface. HLA proteins allow the immune system to determine whether the presenting cell is “self” or “foreign”. Removing HLA proteins is like wrapping the foreign cell with an invisible cloak, rendering it unnoticeable by the immune system. In his talk at the Stem Cell Symposium, Russell discussed the many advantages of using these “universal donor cells (UDCs)” to treat diseases. Only one cell line is needed, which reduces the cost, complexity and time required for clinical trials. Also, it does not require immunosuppression, which weakens the patient’s immune system. Russell and many others believe that UDCs are the future of regenerative medicine. In fact, UDC-based therapies to treat cancer, macular degeneration, skin wounds and type 1 diabetes are already being developed.

It is amazing to see how far we have come over the last 20 years. Thanks to visionary scientists like James Thomson, Shinya Yamanaka, David Russell—and countless other principal investigators, post-docs and grad students who work tirelessly in the lab every day—treatments for many life-threatening diseases may be available in the near future. Nonetheless, there is still much more to learn and many more challenges to overcome. Who knows where the next 20 years will take us?

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How to Reduce Cell Culture Variability

Scenario 1: Jake needs a flask of MCF-7 cells for an assay, so he sends an email to the graduate student listserv asking for cells. Melissa replies that she has an extra flask of cells that she could share. Jake happily accepts the cells and begins his experiment.

Scenario 2: Michael passaged his cells yesterday and, according to the protocol, was supposed to plate cells today for treatment. However, his previous experiments were delayed, so he decides to plate them tomorrow instead. The cells look healthy, so it should be ok.

What is wrong with the above scenarios? These actions may seem harmless, but they could be the cause of variability, leading to irreproducible results. Continue reading →

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Weird samples? Contact Tech Serv to find the right DNA purification kit for you.

“Dear Tech Serv,
We would like to detect DNA collected from swabs rubbed on the inside thighs of frogs. What would be the best DNA extraction kit to use for this?”

“Hi Tech Serv,
I need to find out a suitable kit for extracting DNA from bird fecal samples. Can I use ReliaPrep™ gDNA Tissue Miniprep System for that?”

These are just some examples of unconventional sample type inquiries that the Promega Technical Services Team receives regularly from scientists around the world. Many of these inquiries land in the hands of Technical Services Scientist, Paraj Mandrekar (a.k.a. “sample type guru”). Continue reading →

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A Virus-like Neural Pathway Hints at the Origins of the Mammalian Brain

The mammalian brain is extremely complex. We know that it processes and stores information through synaptic connections within a complicated neural network. But how exactly do neurons communicate with each other? And how did this neural network come to exist? A recent paper published in Cell may provide some answers. It describes a previously unknown signaling pathway–with surprising origins–that transports RNA between neurons. Continue reading →

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Top 5 Most Read Promega Papers in 2017

It’s always nice to know that someone is reading your paper. It’s a sign that your research is interesting, useful and actually has an impact on the scientific community. We were thrilled to learn that papers published by Promega scientists made the top 10 most read papers of 2017 in the journal ACS Chemical Biology. In fact, Promega scientists authored five of the top six most read papers! Let’s take a look at what they are.

#5 CRISPR-Mediated Tagging of Endogenous Proteins with a Luminescent Peptide

Publication Date (Web): September 11, 2017

This 2017 paper introduces our newest star: HiBiT, a tiny 11aa protein tag. To any scientist studying endogenous protein expression, the HiBiT Tagging System is your dream come true. It combines quantitative and highly sensitive luminescence-based measurement with a tiny-sized tag that can be easily inserted into endogenous protein via CRISPR/Cas9 gene editing with little impact on native protein function. The HiBiT Tagging System has been listed as a 2017 Top 10 Innovation by The Scientist, and it will drastically change how we study endogenous protein expression. Continue reading →

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Using CellTiter-Glo® Luminescent Cell Viability Assay to Assess Cell Viability in Cancer Cells Treated with Silver Nanoparticles and DNA-PKcs Inhibitor

Silver nanoparticles (Ag-np) are commonly used in many consumer products, including cosmetics, textiles, electronics and medicine, largely due to their antimicrobial properties. More recently, Ag-np are being used to target and kill cancer cells. It has been known for years that silver nanoparticles (Ag-np) can induce cell death and DNA damage. Studies have also shown that Ag-np inhibit cell proliferation and induce apoptosis in cancer cells. However, cancer cells are able to fight back with DNA repair mechanisms such as non-homologous end joining repair (NHEJ). The NHEJ pathway requires the activation of DNA-dependent protein kinase catalytic subunit (DNA-PKcs), thus DNA-PKcs may protect against the Ag-np-induced DNA damage in cancer cells.

Could inhibition of DNA-PKcs increase the ability of Ag-np to kill cancer cells? In a 2017 study, Lim et al. wanted to test whether inhibition of DNA-PKcs can increase the cytotoxic effect of Ag-np in breast cancer and glioblastoma cell lines. To effectively determine cell viability in these cancer cell lines, the authors used the CellTiter-Glo® Luminescent Cell Viability Assay. The CellTiter-Glo® Assay determines the number of viable cells in culture based on quantitation of ATP, an indicator of metabolically active cells. A major advantage of this assay is its simplicity. This plate-based assay involves adding the single reagent (CellTiter-Glo® Reagent) directly to cells cultured in serum-supplemented medium. This generates a luminescent signal proportional to the amount of ATP present, which is detected using a luminometer. Cell washing, removal of medium and multiple pipetting steps are not required. Another advantage of the CellTiter-Glo® Assay is its high sensitivity. The system detects as few as 15 cells/well in a 384-well format in 10 minutes after adding reagent and mixing, making it ideal for automated high-throughput screening, cell proliferation and cytotoxicity assays.

The authors first confirmed that Ag-np treatment reduced proliferation and induced cell death/DNA damage in two breast cancer cell lines and two glioblastoma cell lines. The cytotoxic effect of Ag-np is specific to cancer cells, as minimal cytotoxicity was observed in non-cancerous human lung fibroblasts used as control. Next, they pre-treated the cancer cells with a DNA-PKcs inhibitor for 1 hour before adding Ag-np. Inhibition of DNA-PKcs increased Ag-np-mediated cell death in all four cancer cell lines. This suggests that DNA-PKcs may be protecting the cells from Ag-np cytotoxicity. The authors further showed that DNA-PKcs may repair Ag-np induced DNA damage by NHEJ and JNK1 pathways. In addition, DNA-PKcs may help recruit DNA repair machinery to damaged telomeres.

This study suggests that a combination of Ag-np treatment and DNA-PKcs inhibition may be a potential strategy to enhance the anticancer effect of Ag-np.

Reference: Hande M.P., et.al. (2017) DNA-dependent protein kinase modulates the anti-cancer properties of silver nanoparticles in human cancer cells. Mutat Res Gen Tox En. 824, 32