Tumor growth inhibition-overall survival modeling in non-small cell lung cancer: A case study from GEMSTONE-302.

Overall survival is vital for approving new anticancer drugs but is often impractical for early-phase studies. The tumor growth inhibition-overall survival (TGI-OS) model could bridge the gap between early- and late-stage development. This study aimed to identify an appropriate TGI-OS model for patients with non-small cell lung cancer from the GEMSTONE-302 study of sugemalimab. We used three TGI models to delineate tumor trajectories and investigated three OS model for linking TGI metric to OS. All three TGI models accurately captured tumor profiles at the individual level. The published atezolizumab-based TGI-OS model predicted survival time satisfactorily through simulation-based evaluation, whereas the other published model built from multi-treatment underestimated OS. Our study-specific TGI-OS model identified time-to-growth as the most significant metric with the number of metastatic sites and neutrophil-to-lymphocyte ratio at baseline as covariates and exhibited robust OS predictability. Our findings demonstrated the effectiveness of the TGI-OS models in predicting phase III outcomes, which underpins their value as a powerful tool for antitumor drug development.

Can a propensity score matching method be applied to assessing efficacy from single-arm proof-of-concept trials in oncology?

As a result of the escalating number of new cancer treatments being developed and competition among pharmaceutical companies, decisions regarding how to proceed with phase III trials are frequently based on findings from either single-arm phase I expansion cohorts or phase II studies that compare the efficacy of the study drug to a standard-of-care benchmark derived from historical data. However, even when eligibility criteria are matched, differences in the distribution of baseline patient features may influence the outcome of single-arm trials in real-world scenarios. Therefore, novel methods are needed to enhance the accuracy of efficacy prediction from current cohorts relative to historical data. In this study, we demonstrated the feasibility of using the propensity score matching (PSM) method to improve decision making by matching relevant baseline features between current and historical cohorts. According to our findings, utilizing the PSM method may provide a less biased means of comparing outcomes between current and historical cohorts relative to a naïve approach, which relies solely on differences in average outcomes between the cohorts.

Active regulation of receptor ratios controls integration of quorum-sensing signals in Vibrio harveyi.

Quorum sensing is a chemical signaling mechanism used by bacteria to communicate and orchestrate group behaviors. Multiple feedback loops exist in the quorum-sensing circuit of the model bacterium Vibrio harveyi. Using fluorescence microscopy of individual cells, we assayed the activity of the quorum-sensing circuit, with a focus on defining the functions of the feedback loops. We quantitatively investigated the signaling input-output relation both in cells with all feedback loops present as well as in mutants with specific feedback loops disrupted. We found that one of the feedback loops regulates receptor ratios to control the integration of multiple signals. Together, the feedback loops affect the input-output dynamic range of signal transmission and the noise in the output. We conclude that V. harveyi employs multiple feedback loops to simultaneously control quorum-sensing signal integration and to ensure signal transmission fidelity.

Measurement of the copy number of the master quorum-sensing regulator of a bacterial cell.

Quorum-sensing is the mechanism by which bacteria communicate and synchronize group behaviors. Quantitative information on parameters such as the copy number of particular quorum-sensing proteins should contribute strongly to understanding how the quorum-sensing network functions. Here, we show that the copy number of the master regulator protein LuxR in Vibrio harveyi can be determined in vivo by exploiting small-number fluctuations of the protein distribution when cells undergo division. When a cell divides, both its volume and LuxR protein copy number, N, are partitioned with slight asymmetries. We measured the distribution functions describing the partitioning of the protein fluorescence and the cell volume. The fluorescence distribution is found to narrow systematically as the LuxR population increases, whereas the volume partitioning is unchanged. Analyzing these changes statistically, we determined that N = 80-135 dimers at low cell density and 575 dimers at high cell density. In addition, we measured the static distribution of LuxR over a large (3000) clonal population. Combining the static and time-lapse experiments, we determine the magnitude of the Fano factor of the distribution. This technique has broad applicability as a general in vivo technique for measuring protein copy number and burst size.

Multiphoton fluorescence and second harmonic generation microscopy for imaging infectious keratitis.

The purpose of this study is to demonstrate the application of multiphoton fluorescence and second harmonic generation (SHG) microscopy for the ex-vivo visualization of human corneal morphological alterations due to infectious processes. The structural alterations of both cellular and collagenous components can be respectively demonstrated using fluorescence and SHG imaging. In addition, pathogens with fluorescence may be identified within turbid specimens. Our results show that multiphoton microscopy is effective for identifying structural alterations due to corneal infections without the need of histological processing. With additional developments, multiphoton microscopy has the potential to be developed into an imaging technique effective in the clinical diagnosis and monitoring of corneal infections.

Multiphoton autofluorescence and second-harmonic generation imaging of the ex vivo porcine eye.

PURPOSE: The purpose of this work was to demonstrate the use of the combined imaging modality of multiphoton autofluorescence and second-harmonic generation (SHG) microscopy in obtaining spectrally resolved morphologic features of the cornea, limbus, conjunctiva, and sclera in whole, ex vivo porcine eyes. METHODS: The 780-nm output of a femtosecond, titanium-sapphire laser was used to induce broadband autofluorescence (435-700 nm) and SHG (390 nm) from various regions of the surface of ex vivo porcine eyes. A water-immersion objective was used for convenient imaging of the curved surface of the eye. RESULTS: Multiphoton autofluorescence was useful in identifying cellular structures of the different domains of the ocular surface, and the SHG signal can be used to resolve collagen organization within the cornea stroma and sclera of ex vivo porcine eyes. CONCLUSIONS: Multiphoton autofluorescence and SHG microscopy have been demonstrated to be an effective technique for resolving, respectively, the cellular and collagen structures within the ocular surface of ex vivo porcine eyes. SHG imaging resolved the difference in structural orientations between corneal and sclera collagen fibers. Specifically, the corneal collagen is organized in a depth-dependent fashion, whereas the scleral collagen is randomly packed. Because this technique does not require histologic preparation procedures, it has the potential to be applied for in vivo studies with minimal disturbance to the eye.

Imaging human bone marrow stem cell morphogenesis in polyglycolic acid scaffold by multiphoton microscopy.

The noninvasive imaging of tissue engineering constructs is vital for understanding the physiological changes in construct formation and the design of improved products for therapeutic purposes. In this work, we use the combination of multiphoton autofluorescence and second harmonic generation (SHG) microscopy to image the physiological changes to the engineered constructs of human mesenchymal stem cells seeded in a polyglycolic acid (PGA) scaffold under induction by chondrogenic transforming growth factor-beta3. Without histological procedures, we found that multiphoton autofluorescence is useful for imaging the PGA scaffold and stem cells while SHG is useful for following the progress of extracellular matrix (ECM) formation. We found that the initial ECM formation tends to align along the PGA scaffold orientation and progressive induction alters the scaffold conformation, indicating that biomechanical forces or the chemical environment generated by chondrogenesis is sufficient for scaffold reorganization. Our results suggest that in the future this approach may be used for real-time monitoring of the physiological processes associated with tissue engineering.

Intact corneal stroma visualization of GFP mouse revealed by multiphoton imaging.

The aim of this work is to demonstrate that multiphoton microscopy is a preferred technique to investigate intact cornea structure without slicing and staining. At the micron resolution, multiphoton imaging can provide both large morphological features and detailed structure of epithelium, corneal collagen fibril bundles and keratocytes. A large area multiphoton cross-section across an intact eye excised from a GFP mouse was obtained by a homebuilt multiphoton microscope. The broadband multiphoton fluorescence (435-700 nm) and second harmonic generation (SHG, 360-400 nm) signals were generated by the 760 nm output of a femtosecond titanium-sapphire laser. A water immersion objective (Fluor, 40X, NA 0.8; Nikon) was used to facilitate imaging the curve ocular surface. The multiphoton image over entire cornea provides morphological information of epithelial cells, keratocytes, and global collagen orientation. Specifically, our planar, large area multiphoton image reveals a concentric pattern of the stroma collagen, indicative of the laminar collagen organization throughout the stroma. In addition, the green fluorescence protein (GFP) labeling contributed to fluorescence contrast of cellular area and facilitated visualizing of inactive keratocytes. Our results show that multiphoton imaging of GFP labeled mouse cornea manifests both morphological significance and structural details. The second harmonic generation imaging reveals the collagen orientation, while the multiphoton fluorescence imaging indicates morphology and distribution of cells in cornea. Our results support that multiphoton microscopy is an appropriate technology for further in vivo investigation and diagnosis of cornea.

Characterizing the thermally induced structural changes to intact porcine eye, part 1: second harmonic generation imaging of cornea stroma.

We characterize the structural changes of porcine corneal structures from 25 to 90 degrees C using second harmonic generation (SHG) microscopy. Our results show that porcine stroma undergoes several distinct stages of structural changes between 25 and 90 degrees C. A decrease in SHG intensity from 30 to 45 degrees C and the existence of SHG intensity peaks at 53, 65, and 77 degrees C correlate to distinct structural alterations of the corneal stroma. At higher temperatures, the SHG intensity decreases and a baseline in SHG signal is reached at 90 degrees C. Our results demonstrate that SHG microscopy is a useful technique for obtaining qualitative and quantitative information of thermally treated corneal fibers without histological or labeling procedures. With additional developments, SHG imaging may be developed into an effective imaging technique for in vivo characterization of cornea structural changes.

Robust circadian oscillations in growing cyanobacteria require transcriptional feedback.

The remarkably stable circadian oscillations of single cyanobacteria enable a population of growing cells to maintain synchrony for weeks. The cyanobacterial pacemaker is a posttranslational regulation (PTR) circuit that generates circadian oscillations in the phosphorylation state of the clock protein KaiC. Layered on top of the PTR is transcriptional-translational feedback regulation (TTR), common to all circadian systems, consisting of a negative feedback loop in which KaiC regulates its own production. We found that the PTR circuit is sufficient to generate oscillations in growing cyanobacteria. However, in the absence of TTR, individual oscillators were less stable and synchrony was not maintained in a population of cells. Experimentally constrained mathematical modeling reproduced sustained oscillations in the PTR circuit alone and demonstrated the importance of TTR for oscillator synchrony.