Translational and oncologic significance of tertiary lymphoid structures in pancreatic adenocarcinoma.

Pancreatic adenocarcinoma (PDAC) is an aggressive tumor with poor survival and limited treatment options. PDAC resistance to immunotherapeutic strategies is multifactorial, but partially owed to an immunosuppressive tumor immune microenvironment (TiME). However, the PDAC TiME is heterogeneous and harbors favorable tumor-infiltrating lymphocyte (TIL) populations. Tertiary lymphoid structures (TLS) are organized aggregates of immune cells that develop within non-lymphoid tissue under chronic inflammation in multiple contexts, including cancers. Our current understanding of their role within the PDAC TiME remains limited; TLS are complex structures with multiple anatomic features such as location, density, and maturity that may impact clinical outcomes such as survival and therapy response in PDAC. Similarly, our understanding of methods to manipulate TLS is an actively developing field of research. TLS may function as anti-tumoral immune niches that can be leveraged as a therapeutic strategy to potentiate both existing chemotherapeutic regimens and potentiate future immune-based therapeutic strategies to improve patient outcomes. This review seeks to cover anatomy, relevant features, immune effects, translational significance, and future directions of understanding TLS within the context of PDAC.

Admission Lymphopenia Predicts Infectious Complications and Mortality in Traumatic Brain Injury Victims.

BACKGROUND: Traumatic brain injury (TBI) is a major cause of mortality and disability associated with increased risk of secondary infections. Identifying a readily available biomarker may help direct TBI patient care. Herein, we evaluated whether admission lymphopenia could predict outcomes of TBI patients. METHODS: This is a 10-year retrospective review of TBI patients with a head Abbreviated Injury Score 2 to 6 and absolute lymphocyte counts (ALC) collected within 24 h of admission. Exclusion criteria were death within 24 h of admission and presence of bowel perforation on admission. Demographics, admission data, injury severity score, mechanism of injury, and outcomes were collected. Association between baseline variables and outcomes was analyzed. RESULTS: We included 2,570 patients; 946 (36.8%) presented an ALC ≤1,000 on admission (lymphopenic group). Lymphopenic patients were significantly older, less likely to smoke, and more likely to have heart failure, hypertension, or chronic kidney disease. Lymphopenia was associated with increased risks of mortality (OR = 1.903 [1.389-2.608]; P < 0.001) and pneumonia (OR = 1.510 [1.081-2.111]; P = 0.016), increased LOS (OR = 1.337 [1.217-1.469]; P < 0.001), and likelihood of requiring additional healthcare resources at discharge (OR = 1.669 [1.344-2.073], P < 0.001). Additionally, lymphopenia increased the risk of early in-hospital death (OR = 1.459 [1.097-1.941]; P = 0.009). Subgroup analysis showed that lymphopenia was associated with mortality in polytrauma patients and those who presented with two or more concurrent types of TBI. In all subgroup analyses, lymphopenia was associated with longer length of stay and discharge requiring higher level of care. CONCLUSION: A routine complete blood count with differential for all TBI patients may help predict patient outcomes and direct care accordingly.

Modeling the Effects of Hemodynamic Stress on Circulating Tumor Cells using a Syringe and Needle.

During metastasis, cancer cells from solid tissues, including epithelia, gain access to the lymphatic and hematogenous circulation where they are exposed to mechanical stress due to hemodynamic flow. One of these stresses that circulating tumor cells (CTCs) experience is fluid shear stress (FSS). While cancer cells may experience low levels of FSS within the tumor due to interstitial flow, CTCs are exposed, without extracellular matrix attachment, to much greater levels of FSS. Physiologically, FSS ranges over 3-4 orders of magnitude, with low levels present in lymphatics (<1 dyne/cm2) and the highest levels present briefly as cells pass through the heart and around heart valves (>500 dynes/cm2). There are a few in vitro models designed to model different ranges of physiological shear stress over various time frames. This paper describes a model to investigate the consequences of brief (millisecond) pulses of high-level FSS on cancer cell biology using a simple syringe and needle system.

Cancer Cells Resist Mechanical Destruction in Circulation via RhoA/Actomyosin-Dependent Mechano-Adaptation.

During metastasis, cancer cells are exposed to potentially destructive hemodynamic forces including fluid shear stress (FSS) while en route to distant sites. However, prior work indicates that cancer cells are more resistant to brief pulses of high-level FSS in vitro relative to non-transformed epithelial cells. Herein, we identify a mechano-adaptive mechanism of FSS resistance in cancer cells. Our findings demonstrate that cancer cells activate RhoA in response to FSS, which protects them from FSS-induced plasma membrane damage. We show that cancer cells freshly isolated from mouse and human tumors are resistant to FSS, that formin and myosin II activity protects circulating tumor cells (CTCs) from destruction, and that short-term inhibition of myosin II delays metastasis in mouse models. Collectively, our data indicate that viable CTCs actively resist destruction by hemodynamic forces and are likely to be more mechanically robust than is commonly thought.

Arg188 drives RhoC membrane binding.

RhoA and RhoC GTPases are 92% identical but demonstrate unique regulation and function. Phosphorylation of Ser188 has widely been reported to inhibit RhoA activity. RhoC possesses Arg188 in place of Ser188 but retains a canonical upstream PKA recognition sequence. We report here that RhoC-R188S was a PKA substrate in vitro and exhibited less GTP loading compared to wild-type RhoC when expressed in cells. Transiently expressed RhoC was found to be significantly more membrane associated than RhoA. Membrane association of RhoC-R188S and RhoC-R188A were similar to each other and wild-type RhoA, suggesting that Arg188 directly promotes RhoC membrane binding. The positive influence of Arg188 on RhoC membrane association was evident in a constitutively active (Q63L) background. In accordance, RhoA-S188R was significantly more membrane associated than either RhoA or RhoA-S188A. Altogether, these data suggest that swapping residue 188 identity effectively flips the membrane binding profile of wild-type RhoA and RhoC through positive arginine contribution rather than negative phosphoserine regulation.