Tag: Medication

Diphtheria toxin receptor (DTR)–based depletion models are widely used to study microglial and macrophage function, yet the extent to which diphtheria toxin (DT) produces off-target effects remains incompletely defined. Here, we examined tolerability, behavioural outcomes, and cellular responses following intracerebroventricular (i.c.v.) DT administration in wild-type (WT) and CD11b-DTR mice. Mice received bilateral i.c.v. infusions of DT or vehicle over a 10-day period and were assessed for survival, motor and cognitive behaviour, myeloid cell changes, and neuropathology. Unexpectedly, DT induced dose-dependent mortality in WT mice, demonstrating that toxicity can occur independently of DTR expression. CD11b-DTR mice exhibited greater susceptibility, with reduced survival and the emergence of illness at lower DT doses. Behavioural testing revealed significant dose-dependent impairments in rotarod performance and Y-maze spontaneous alternation in both genotypes, while open-field mobility was largely preserved among animals. Region-specific analysis of myeloid cells in CD11b-DTR mice showed robust depletion in the midbrain at higher DT doses, whereas hippocampal cell numbers remained unchanged with marked morphological signs of activation. These findings indicate that DT-mediated myeloid cell responses vary across brain regions, potentially reflecting differential toxin exposure following ventricular delivery. Consistent with this, focal abnormalities in the brain—including ventriculitis, meningoencephalitis and spongiotic changes—were observed in a subset of clinically affected DT-treated animals, whereas peripheral organs were largely unremarkable and haematological changes were infrequent. Together, these data demonstrate that i.c.v. DT administration can induce mortality, behavioural dysfunction, and focal CNS pathology in both WT and CD11b-DTR mice, with transgene expression amplifying susceptibility. Our findings highlight the need for careful dose optimisation, appropriate DT-treated controls, and cautious interpretation of behavioural phenotypes when employing this model.

A new study published in Nature Communications is reshaping how researchers think about metastasis, showing that the cells most likely to spread are not defined by extremes, but by a precise balance of biological states within the primary tumor.

The work, led by Raúl Jiménez Castaño, PhD, and colleagues in the Cell Plasticity in Development and Disease Laboratory headed by Ángela Nieto at the Instituto de Neurociencias in Spain, identifies a nonlinear relationship between expression of the transcription factor Prrx1 and metastatic potential in breast cancer. Tumors with intermediate levels of Prrx1—not low or high—were found to be the most metastatic.

“This is unusual,” Jiménez Castaño said. “You normally expect a linear correlation—either low or high expression being the most relevant. But here, the peak of metastasis is in the intermediate levels.”

From paradox to mechanism

The study builds on longstanding efforts to understand the epithelial-to-mesenchymal transition (EMT), a developmental program that enables cells to migrate and is co-opted by cancer cells during metastasis. While EMT has been widely linked to tumor dissemination, the new findings show that metastatic potential is not simply a function of how invasive a cell becomes. Instead, it depends on a finely tuned balance between invasion and proliferation—two processes that are often at odds.

Previous work from the group and others had produced conflicting results regarding the role of Prrx1. In some models, removing the gene reduced metastasis; in others, it appeared necessary for dissemination. To resolve this contradiction, the researchers turned to patient tumor samples, where they observed that metastatic incidence peaked in tumors with intermediate Prrx1 expression.

Modeling a metastatic “sweet spot”

To investigate, the team engineered mouse models with graded levels of Prrx1 expression, mimicking the spectrum observed in human tumors. The results closely mirrored patient data. Tumors lacking Prrx1 showed little ability to metastasize, while those with high expression were capable of invasion but produced relatively few metastases. In contrast, tumors with intermediate levels generated the highest metastatic burden.

At the invasive front of these tumors, the researchers identified a distinct population of cells capable of both migrating and adopting divergent fates—either proliferating or entering a dormant state. This balance proved to be the critical determinant of metastatic success.

To understand the underlying biology, the team applied a range of advanced techniques, including single-cell RNA sequencing, chromatin profiling, and spatial transcriptomics. These approaches allowed them to map cellular states within tumors and link Prrx1 expression levels to functional behavior.

The analyses revealed that Prrx1 plays a dual role: it promotes invasion while simultaneously activating a dormancy program that suppresses cell division.

“At the same time that Prrx1 is necessary for cancer cells to be invasive, it also activates a dormancy program,” Jiménez Castaño explained.

This creates a biological trade-off. At high Prrx1 levels, cells are highly invasive but largely non-proliferative, limiting their ability to form metastases. At low levels, cells retain proliferative capacity but cannot effectively disseminate. Only at intermediate levels do cells achieve both capabilities.

“If the cancer cell has these intermediate levels, it is both invasive and proliferative,” he said. “And therefore, these cells will create a lot of metastasis.”

Metastatic potential begins in the primary tumor

One of the study’s most significant implications is that metastatic potential is determined earlier than previously appreciated. Rather than being dictated solely by conditions at distant sites, the ability of cancer cells to form metastases appears to be encoded within specific cell states in the primary tumor.

“The big conclusion is that already in the primary tumor, the potential of the cancer cells to metastasize is defined,” Jiménez Castaño said.

This finding aligns with broader observations from the field that tumors contain heterogeneous populations of cells with distinct functional properties. In this case, a subset of cells with intermediate Prrx1 expression represents a particularly dangerous state—one that combines mobility with the capacity for sustained growth.

Implications for biomarkers and therapy

Although the study identifies Prrx1 as a potential marker of metastatic risk, translating this insight into clinical practice will require further validation. The researchers were able to stratify tumors into low, intermediate, and high expression groups using staining intensity and computational analysis, but defining precise thresholds remains a challenge.

“We cannot say at this moment it is a biomarker,” Jiménez Castaño noted.

Even so, the findings provide a conceptual framework for improving patient stratification and identifying tumors with a higher likelihood of metastasis.

They also suggest new therapeutic strategies. Rather than attempting to eliminate invasive behavior entirely, it may be possible to push tumor cells into states that are less capable of forming metastases. For example, maintaining high Prrx1 expression could promote invasion while simultaneously enforcing dormancy, preventing metastatic outgrowth.

The post Breast Cancer Cell Metastatic State Characterized by Prrx1 Levels appeared first on Inside Precision Medicine.

mRNA vaccines scored a stunning win against SARS-CoV-2 in 2020, and now the Nobel-prize–winning technology is out to conquer some cancers. Several mRNA vaccines are already in clinical trials for melanoma, small cell lung cancer, and bladder cancer, among others. Recently, a pancreatic cancer vaccine grabbed headlines after researchers shared that most Phase I trial participants were still alive after several years—unprecedented in a disease that is considered incurable, and usually kills patients quickly.

But how exactly does mRNA work? A new study suggests a broader role for how T cells become activated after an mRNA vaccine. It’s a process that engages both cDC1 and cDC2 cells redundantly. The study was led by researchers at Washington University School of Medicine in St. Louis (WashU) and could lead to improvements in mRNA vaccine design. The findings were published in Nature. The work was powered by a novel mouse model developed by the WashU team.

“My lab made them in 2019 and 2022. We put all of them in Jackson labs [database] so anyone can get them, no strings, and study them,” senior author Kenneth M. Murphy, MD, PhD, told Inside Precision Medicine. “Thanks to them, we saw the question and were able to address it most quickly.”

Until now, scientists assumed that cDC1, which is a classical type 1 dendritic cell, was required for mRNA vaccination to activate the immune system. But, in a lab study, these researchers found that even without cDC1 cells, the mRNA vaccine still triggers strong cancer‑killing responses. That’s because they determined that cDC2, a cousin to cDC1, can also stimulate anti-tumor immune activity—an unexpected finding given that this related subtype is not involved in responses to other vaccines.

“There is a lot of interest in applying the mRNA vaccine approaches used during the COVID-19 pandemic to the problem of inducing anti-tumor immunity,” said Murphy, the Eugene Opie Centennial Professor in the department of pathology & immunology at WashU Medicine. “By dissecting which immune cells are involved and how they coordinate the response, we’re offering vaccine developers some additional mechanistic insights to consider in their goal of optimizing these vaccines against tumor proteins.”

Murphy is also a research member at Siteman Cancer Center, based at Barnes-Jewish Hospital and WashU Medicine.

mRNA vaccines work by delivering instructions, in the form of messenger RNA, for immune cells to produce bits of protein that trigger the immune system to destroy cells bearing these proteins. Dendritic cells produce the protein bits from the mRNA instructions, and T cells then find and destroy the invading proteins. To treat cancer, mRNA vaccines can be designed to generate protein bits unique to a tumor.

The work was done in collaboration with the study’s co-corresponding author, William E. Gillanders, MD, the Mary Culver Professor of Surgery at WashU Medicine. Gillanders, a physician-scientist and surgical oncologist who has also developed an investigational vaccine against triple-negative breast cancer, treats patients at Siteman Cancer Center.

Murphy and members of his lab used their mouse models, which lacked cDC1 or cDC2, to tease out the role that different groups of dendritic cells play in priming T cells after mRNA cancer vaccination.

One of their findings was that mice immunized with an mRNA vaccine generated strong T-cell responses even in the absence of cDC1s. In addition, they found that immunized mice without cDC1s were able to clear sarcoma tumors—cancers that develop in connective tissues such as fat, muscle, nerves, blood vessels, bone, and cartilage. This indicated that some other cell type must be stimulating the T-cell response.

Indeed, their study found that cDC2s also participate in generating an immune response from T cells and preventing tumor growth. Further, the study found that T cells turned on by cDC1s and cDC2s each showed slightly different molecular “fingerprints.” These differences could help scientists design better versions of vaccines in the future.

Similarly, immunized mice lacking cDC2s and mice that had both cell subtypes produced an immune response and rejected tumor growth, demonstrating that mRNA vaccination uses both dendritic cell subtypes to stop cancer.

“This work uncovers a new way mRNA vaccines engage the immune system—through both cDC1 and cDC2—which helps explain their power and gives researchers concrete targets for making future mRNA cancer vaccines more effective,” said Gillanders. “It could improve vaccine formulation and dosing, potentially explain why some patients respond better to vaccines than others, and guide strategies for making vaccines more effective.”

The post mRNA Uses Unconventional Pathways in CD8+T Cell Priming to Help Vaccines Work appeared first on Inside Precision Medicine.