Just What Is an RLU (Relative Light Unit)?

This post was contributed by guest blogger, Scott Messenger, Technical Support Scientist 2 at Promega Corporation.

It’s always an exciting time in the lab when you find a new assay to answer an important research question. Once you get your hands on the assay, it is always good to confirm it will work for your experimental setup. Repeating the control experiment shown in the technical manual is a great way to test the assay in your hands.

After running that first experiment of your assay, it looks pretty good. The trends of control and treatment are consistent. Time to get on with the experiments…but wait—the RLUs (Relative Light Units) are two orders of magnitude lower than the example data! I can’t show this data to my colleagues; it doesn’t match. What did I do wrong?

This is a concern that we in Technical Services hear frequently. The concern is real, and I had this same thought when doing some of my first experiments using luminescence. When a question like this comes in, a Technical Service Scientist will make sure the experiment was performed as we described, and in most cases it is. We then start talking about RLUs (Relative Light Units).

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Out-FOXOing High-Stage Neuroblastoma

Fluorescence microscopy of neuroblastoma cells.

In recent years, scientists have been hot on the trail of transcription factor FOXO3, tracing its involvement in various tumor-centric activities comprising the many trademarks of cancer, from drug resistance to metastasis to tumor angiogenesis.

FOXO3 is a member of the O sub-class of the forkhead box family of transcription factors. The forkhead box (FOX) family is characterized by a fork head DNA-binding domain (DBD), comprised of around 100 amino acids. They have also proven themselves to be a family of many hats, functioning in diverse roles ranging from metabolism, immunology, cell-cycle control, development, as well as cancer (1). The forkhead box O (FOXO) sub-class alone has demonstrated involvement in a variety of cellular outcomes, from drug resistance and longevity to apoptosis induction.

Due to its pro-apoptotic and anti-proliferative proclivity, FOXO3 has been previously identified as a tumor suppressor gene. However, more and more studies have begun to flip the narrative on FOXO3, portraying it more as a devoted henchman, due to its roles in drug and radiotherapy resistance, cell-cycle arrest and long-term maintenance of leukemia-initiating stem cells in a variety of cancer types, including breast cancer, pancreatic cancer, glioblastoma, and both acute and chronic myeloid leukemia.

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To inject or not inject?

GloMax® Discover Multimode Reader with injectors.
GloMax® Discover Multimode Reader with injectors.

Luciferase assays are useful tools for studying a wide range of biological questions. They can be performed easily by adding a reagent that provides components necessary to generate a luminescent signal directly to cells or a cell lysate. However, once this reagent has been added, how long you wait to measure the signal becomes a key consideration in generating consistent data. Dependent on which luciferase assay you use, you may need a luminometer that can use injectors to deliver the assay reagents. The reason for this is simple, but can be confusing to new users.

Let’s start by discussing two types of luciferase assays: “flash” vs. “glow”. Continue reading “To inject or not inject?”

Shining a Bright Light on Deep Questions in Biology with Bioluminescence

artists view inside a cellA quick search of the PubMed database for “dual luciferase” quickly returns over 1,000 papers. The Dual-Luciferase® Reporter Assay is a powerful tool that allows researchers to ask a multitude of questions about gene control and expression in a system that itself could be normalized and internally controlled. For more than 15 years, firefly and Renilla luciferases  have formed the basis of a range of powerful assays and research tools for scientists who are asking questions about the deep and complex genetic and cellular story associated with cancer. Here we talk a bit of about bioluminescent chemistries, some of the newest bioluminescent tools available, and how some of these tools can be used to probe the deeper questions of cell biology, including cancer biology. Continue reading “Shining a Bright Light on Deep Questions in Biology with Bioluminescence”