Our Top Three Most-Viewed Blog Posts of 2022

In 2022, our bloggers wrote on topics ranging from monkeypox outbreaks to cultured meat in biotech labs to preventing the next pandemic. Our top three most-viewed blog posts this year have the commonality of Promega products helping to advance important research in different fields and push science a step forward in the world. Take a look at Promega’s top three most-viewed blog posts of 2022.

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Cellular Senescence and Cancer Therapy: Overcoming Immortality?

At the time of writing this post, no scientist had yet discovered the secret to immortality. In our world, we’ve come to accept that living things are born, grow old and die—the circle of life.

And yet, for many years, life scientists believed that the circle of life did not apply to our constituent cells when cultured in a laboratory. That is, cultured normal human cells were immortal, and they would continue to grow and proliferate forever, as long as they were provided with the necessary nutrients.

The animal cell cycle. Image by Kelvinsong; made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication

Pioneering work published in 1961 by Leonard Hayflick and Paul Moorhead challenged that theory (reviewed in 1). Their research showed that normal cells in culture have a finite capacity to replicate. After they reach a certain number of replicative cycles, cells stop dividing. Hayflick and Moorhead made the important distinction between normal human cells and cultured cancer cells, which are truly immortal. In later years, the limit to the number of replicative cycles normal human cells can undergo became known as the Hayflick limit. Although some scientists still express skepticism about these findings, the Hayflick limit is widely recognized as a fundamental principle of cell biology.

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Designing Better Therapeutic mAbs: An Assay for Rapid, Parallel Screening of Fc/ FcɣR Interactions

The first monoclonal antibody (mAb) was produced in a lab 1975, and the first therapeutic mAb was introduced in the United States to prevent kidney transplant rejection in 1986. The first mAb used in cancer treatment the anti-CD20 mAb, rituximab, was used to treat non-Hodgkin’s lymphoma and chronic lymphocytic leukemia. Today therapeutic mAbs have become a mainstay of cancer, autoimmune disease, and metabolic disease therapies and include HERCEPTIN® used to treat certain forms of breast cancer, Prolia used to treat bone loss in post-menopausal women, and Stelara used to treat autoimmune diseases like psoriatic arthritis and severe Crohn disease, among many others. Therapeutic mAbs bind targets with high specificity and affinity and they can recruit effector cells to drive target elimination through mechanisms such as antibody-dependent cellular cytotoxicity (ADCC) or antibody-dependent cellular phagocytosis (ADCP), making them highly specific, effective therapies.

3D rendering of a Lumit Assay which can be used  for plate-based screening assay to measure the affinities of Fc interactions of therapeutic mAbs.
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The Human Cell Atlas: Mapping a Cellular Landscape

From macrophages that seek out and destroy infectious agents to fibroblasts that hold tissues and organs together, cells give form and function to our bodies. However, despite their foundational roles in our biology, there is still much we don’t know about cells—like where different cell types are localized, what states a given cell type may take on, how the molecular characteristics of cells change over a person’s lifetime and more. Addressing these questions will provide a deeper understanding about the cellular and genetic basis of human health and disease.

Image contains several cells with a hazy outline of a DNA molecule in the background and one cell is highlighted
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Cytochrome P450 Inhibition: Old Drug, New Tricks

multiwell screening plate and various pills on a table

Cytochrome P450 (CYP) inhibitors are often used as boosting agents in combination with other drugs. This drug development strategy is front and center for Paxlovid, the new anti-SARS-CoV-2 treatment from Pfizer. Paxlovid is a combination therapy, comprised of two protease inhibitors, nirmatrelvir and ritonavir. It significantly reduces the risk of COVID-19 hospitalization in high-risk adults and is ingested orally rather than injected, which is an advantage over other SARS-CoV-2 treatments, such as Remdesivir.

Nirmatrelvir was originally developed by Pfizer almost 20 years ago to treat HIV and works by blocking enzymes that help viruses replicate. Pfizer created another version of this drug to combat SARS in 2003, but, once that outbreak ended, further development was put on pause until the advent of the COVID-19 pandemic. After developing an intravenous form of nirmatrelvir early in the pandemic, Pfizer created another version that can be taken orally and combined it with ritonavir.

When ritonavir was originally developed, it wasn’t considered particularly useful because it metabolized so quickly in the body. Now it is recognized as a pharmacokinetic enhancer in combination with other drugs. Ritonivir inhibits CYP3A4, an enzyme which plays a key role in the metabolism of drugs and xenobiotics. By inhibiting CYP3A4, ritonivir slows the metabolism of other drugs. In the case of Paxlovid, this allows nirmatrelvir to stay in the body longer at a high enough concentration to be effective against the virus. This ultimately means that patients can be given lower doses of the drug with reducing efficacy.

Diagram of Nirmaltrelvir mechanism of action.
Nirmatrelvir inhibits the viral 3CL protease, so that functional, smaller viral proteins cannot be produced.
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Cultured Meat Viability Increases in Biotech

Cultured meat grows in a plastic dish in laboratory conditions.

The biotechnology industry has been powering through barriers standing between the lab and the dinner plate as cultured meat advances toward the market. Challenges like scaling up the technology and getting products to the market are significant, but future food demands are an even bigger obstacle. Earth’s population is projected to reach 10 billion people by 2050. Our current agricultural practices will not be able to meet the food demands. Therefore, we need to find alternative ways to produce food–like “growing” it in the lab.

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GPCRs and PROTACs: New Approaches for Designing More Effective Drug Candidates

NanoBRET target engagement assay

G protein-coupled receptors (GPCRs) comprise a large group of cell surface receptors, characterized by the unique structural property of crossing the cell membrane seven times. They respond to a diverse group of signaling molecules, such as peptides, neurotransmitters, cytokines, hormones and other small molecules (1). Upon activation, GPCRs interact with GTP-binding (G) proteins and arrestins to regulate a wide variety of signaling pathways. This broad range of functions makes GPCRs attractive targets for drug discovery. The importance of GPCR research was highlighted in 2012, with the Nobel Prize in chemistry being awarded to Robert Lefkowitz and Brian Kobilka “for studies of G-protein–coupled receptors”.

Based on structure and function, GPCRs are categorized into six classes, A–F. The class A GPCRs, or rhodopsin-like receptors, have been studied extensively due to their association with many types of diseases (2). Within the class A GPCRs is a group that share a highly conserved structural motif (3) and respond to chemokines—small “chemotactic cytokines” that stimulate cell migration, especially that of white blood cells (4). A subfamily of class A GPCRs respond to chemokines that have two cysteine residues near the N-terminus, known as CC chemokines. GPCRs activated by CC chemokines are called CC chemokine receptors or CCRs, and these interactions have been implicated in both pro- and anti-cancer pathways (5).

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New Study Suggests Long Mononucleotide Repeat Markers Offer Advantages for Detecting Microsatellite Instability in Multiple Cancers

A new study, published in the Journal of Molecular Diagnostics (1), highlights the potential of using long mononucleotide repeat (LMR) markers for characterizing microsatellite instability (MSI) in several tumor types. The paper is a result of a collaborative effort between researchers from Johns Hopkins University and Promega to evaluate the performance of a panel of novel LMR markers for determining MSI status of colorectal, endometrial and prostate tumor samples.

Microsatellite instability (MSI) is the accumulation of insertion or deletion errors at microsatellites, which are short tandem repeats of DNA sequences found throughout the genome. MSI in cancerous cells is the result of a functional deficiency within one or more major DNA mismatch repair proteins (dMMR). PCR-based MSI testing is a commonly used method that can help understand a tumor’s genomic profile as it relates to MMR protein function.

Historically, MSI has been a biomarker associated with Lynch syndrome, the hereditary predisposition to colorectal and certain other cancers. In recent years, research interest in MSI has exploded, driven by the discovery that its presence in tumor tissue can be predictive of a positive response to anti-PD-1 immunotherapies (2,3).

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Real-Time Analysis for Cell Viability, Cytotoxicity and Apoptosis: What Would You Do with More Data from One Sample?

Originally posted May 25, 2017. Updated 2022

You are studying the effects of a compound(s) on your cells. You want to know how the compound affects cell health over a period of hours, or even days. Real-time assays allow you to monitor cell viability, cytotoxicity and apoptosis continuously, to detect changes over time.

Why use a real-time assay?
A real-time assay enables you to repeatedly measure specific events or conditions over time from the same sample or plate well. Repeated measurement is possible because the cells are not harmed by real-time assay reagents. Real-time assays allow you to collect data without lysing the cells.

Advantages of  Real-Time Measurement
Real-time assays allow you to:

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MISpheroID: A Knowledgebase to Improve Reproducibility in Spheroid Research

Spheroid research is  now a common component of cell biology and drug discovery science

Advantages of Spheroids

In the past decade, there has been a sharp rise in studies using spheroids as cell models for basic research and drug discovery. Spheroids are self-organized aggregation of cells that form a spherical mass, and they have become widely popular because they are much more physiologically relevant compared to flat 2D cell cultures.

In spheroids, the inner cells have less access to nutrients and oxygen compared to the outer layer, forming a natural gradient. As a result, metabolite concentration and cellular state such as proliferation and differentiation, can be very different at the periphery compared to the inner core. This phenomenon, known as “heterogeneity”, makes 3D tumor spheroids much more representative of actual tumors in the human body.

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