Biology subjects

Sivakumar, H.

Publications and source records attributed to Sivakumar, H..

5 recordsLinked to original sources

bioRxiv2026

Establishment of a patient-derived adrenocortical carcinoma 3D tumor construct platform for evaluation of therapeutic strategies

Adrenocortical carcinoma (ACC) is an under-studied, aggressive cancer of the adrenal glands where surgical resection is currently the only effective curative option. However, after surgery the majority of patients experience tumor progression. The median overall survival of 12 months has not improved since approval of mitotane in 1970. The lack of effective therapies in ACC is partially due to the lack of preclinical models that accurately represent human ACC. Most attempts to generate ACC cell lines or animal models have been unsuccessful. The few existing models do not adequately reflect the oncogenic signaling pathways or intratumoral heterogeneity of human ACC. These limited model systems have hindered identification of drivers of tumor progression and immune escape mechanisms, thereby limiting development and testing of novel therapeutic approaches such as targeted therapies or immunotherapies. We developed human ACC patient-derived tumor constructs (PTCs) encapsulated in synthetic extracellular matrix. Our ACC PTCs exhibit hallmarks of ACC: proliferation, expression of key ACC biomarkers, such as SF1, and production of cortisol. We provide characterization in the form of immunofluorescence staining for ACC biomarkers, and confirmation of PTC proliferation and cortisol production - a hallmark of ACC. We then demonstrate the utility of ACC PTCs for evaluation of chemotherapies currently used clinically (mitotane) with and without experimental cocktails of etoposide, doxorubicin, and cisplatin, experimental targeted therapies, and cellular immunotherapies, primarily in the form of natural killer (NK) cell therapy. In particular, the latter - cellular immunotherapies - are cutting edge studies demonstrating potential to evaluate immunotherapies in ACC clinical scenarios. Together these data provide evidence that patient-derived ACC models can serve as an important tool for identification of future points of intervention and testing of novel therapeutic strategies to improve ACC clinical care.

cancer biology↗

bioRxiv2023

A 3D adrenocortical carcinoma tumor platform for preclinical modeling of drug response and matrix metalloproteinase activity

Adrenocortical carcinoma (ACC) has a poor prognosis, and no new drugs have been identified in decades. The absence of drug development can partly be attributed to a lack of preclinical models. Both animal models and 2D cell cultures of ACC fail to accurately mimic the disease, as animal physiology is inherently different than humans, and 2D cultures fail to represent the crucial 3D architecture. Organoids and other small 3D in vitro models of tissues or tumors can model certain complexities of human in vivo biology; however, this technology has largely yet to be applied to ACC. In this study, we describe the generation of 3D tumor constructs from an established ACC cell line, NCI-H295R. NCI-H295R cells were encapsulated to generate 3D ACC constructs. Tumor constructs were assessed for biomarker expression, viability, proliferation, and cortisol production. In addition, matrix metalloproteinase (MMP) functionality was assessed directly using fluorogenic MMP-sensitive biosensors and through infusion of NCI-H295R cells into a metastasis-on-a-chip microfluidic device platform. ACC tumor constructs showed expression of biomarkers associated with ACC, including SF-1, Melan A, and inhibin . Treatment of ACC tumor constructs with chemotherapeutics demonstrated decreased drug sensitivity compared to 2D cell culture. Since most tumor cells migrate through tissue using MMPs to break down extracellular matrix, we validated the utility of ACC tumor constructs by integrating fluorogenic MMP-sensitive peptide biosensors within the tumor constructs. Lastly, in our metastasis-on-a-chip device, NCI-H295R cells successfully engrafted in a downstream lung cell line-based construct, but invasion distance into the lung construct was decreased by MMP inhibition. These studies, which would not be possible using 2D cell cultures, demonstrated that NCI-H295R cells secreted active MMPs that are used for invasion in 3D. This work represents the first evidence of a 3D tumor constructs platform for ACC that can be deployed for future mechanistic studies as well as development of new targets for intervention and therapies. SignificanceThe paucity of preclinical research models has contributed to lack of progress in treatment of adrenocortical carcinoma (ACC). Three-dimensional modeling of ACC may provide novel insights for preclinical studies and advance ACC research.

cancer biology↗

bioRxiv2021

Engineering a thixotropic and biochemically tunable hyaluronan and collagen bioink for biofabrication of multiple tissue construct types

The field of three-dimensional (3D) bioprinting has advanced rapidly in recent years. Significant reduction in the costs associated with obtaining functional 3D bioprinting hardware platforms is both a cause and a result of these advances. As such, there are more laboratories than ever integrating bioprinting methodologies into their research. However, there is a lack of standards in the field of biofabrication governing any requirements or characteristics to support cross-compatibility with biomaterial bioinks, hardware, and different tissue types. Here we describe a modular extracellular matrix (ECM) inspired bioink comprised of collagen and hyaluronic acid base components that: 1) employ reversible internal hydrogen bonding forces to generate thixotropic materials that dynamically reduce their elastic moduli in response to increased shear stress, thus enabling increased compatibility with printing hardware; and 2) modular addons in the form of chemically-modified fibronectin and laminin that when covalently bound within the bioink support a variety of tissue types, including liver, neural, muscle, pancreatic islet, and adipose tissue. These features aim to accelerate the deployment of such bioinks for tissue engineering of functional constructs in the hands of various end users.

bioengineering↗

bioRxiv2020

Alleviation of neuropathic pain by over-expressing a soluble colony-stimulating factor 1 receptor

In this study, we aim to alleviate neuropathic pain by suppressing microgliosis and macrophage accumulation, which is achieved by over-expressing a non-functional soluble colony-stimulating factor 1 receptor using adeno-associated virus 9 vectors (AAV9/sCSF1R). AAV9/sCSF1R and AAV9/GFP were intrathecally administered into mouse lumbar spine. Two weeks later, these mice underwent partial sciatic nerve ligation to induce neuropathic pain. GFP and sCSF1R were highly expressed in dorsal root ganglia (DRG) and spinal cords in AAV9-injected mice. Nerve ligation alone or pre-treated with AAV9/GFP led to significant microgliosis in the lumbar spinal cords and macrophage accumulation in DRG and sciatic nerves. In nerve-ligated mice pre- treated with AAV9/sCSF1R the microglia densities in the dorsal and ventral horns and macrophage densities in DRG and sciatic nerves were significantly lower compared to nerve-ligated mice pre-treated with AAV9/GFP. Behavioural tests showed that nerve-ligated mice pre- treated with AAV9/sCSF1R had a significantly higher paw withdrawal threshold, indicating the alleviation of neuropathic pain. The results implicate that viral vector-mediated expression of sCSF1R may represent a novel strategy in long-term alleviation of neuropathic pain.

neuroscience↗

bioRxiv2017

The evolution of p53 network behavior

We study the evolution of the p53 core regulation network across the taxonomic span of humans to protozoans and nematodes. We introduce a new model for the core regulation network in mammalian cells, and conduct a formal analysis of the different network configurations that emerge in the evolutionary path to complexity. Solving the high dimensional equations associated with this model is typically challenging, and we develop a novel algorithm to overcome this problem. A key technical tool used is the representation of the distinct pathways in the core regulation networks as \"modules\", such that the behavior of the composite of two or more modules can be inferred from the characteristics of each of the individual modules. Apart from simplifying the complexity of the algorithm, this modular representation also allows us to qualitatively compare the distinct types of switching behaviors each network can exhibit. This then allows us to demonstrate how our model for the core regulation network in mammalian cells matches experimentally observed phenomena, and contrast this with the plausible behaviors admitted by the network configurations in putative primordial organisms. We show that the complexity of the p53 core regulation network in vertebrates permits a range of behaviors that can bring about distinct cell fate decisions not possible in the putative primordial organisms.\n\nSignificance StatementThe p53 protein has been protecting organisms from tumors for a billion years. We study the link between the evolution of the p53 network structure and its corresponding tumor suppression strategies. We compare the dynamical behaviors in putative primordial organisms with simple networks with the vertebrate network that contains multiple feedback loops. We show that the vertebrate network, but not the ancestral network, can both repair moderate damage and induce apoptosis if too much damage accumulates, balancing the risk of cancer with the cost of too much cell death. Moreover, the complexity of the vertebrate network allows for adaptation, for example to increase p53 network sensitivity, which is consistent with recent research on large mammals.

systems biology↗