👤 Srinivas B Narayan

For decades, platinum chemotherapy was the mainstay of treating metastatic urothelial carcinoma (mUC). More recently, checkpoint inhibitors (CPI) were an important addition to the armamentarium capable of inducing durable responses for a minority of patients. Management of mUC has changed significantly with the advent of antibody-drug conjugate (ADC) therapies and fibroblast growth factor receptor inhibitors (FGFRi). Enfortumab vedotin, a Nectin-4 targeting ADC, is now the first line therapy of choice in combination with pembrolizumab. Erdafitinib, a pan FGFR1-4 inhibitor, is approved for patients with susceptible FGFR3 alterations. There are multiple other agents in development within both therapeutic classes that hold promise. But most patients will still succumb to their disease, either via primary or secondary resistance. This review looks critically at the approved and pipeline ADC and FGFR-targeting agents of interest in mUC as well as known mechanisms of resistance by which their efficacy is dampened. We propose strategies for overcoming resistance including combination strategies, tumor microenvironment modification, and drug structure modification to maximize efficacy. The progress to date in mUC has been remarkable, but there is still significant work to do in this deadly disease and this review highlights the gap between current available therapeutics and cure that so desperately needs to be closed. Show less

The nuclear pore complex is comprised of approximately 30 proteins named nucleoporins (Nups) and tightly regulates nucleocytoplasmic transport of macromolecules across the nuclear membrane. Genetic alterations in many NUP genes are associated with many human maladies, such as neurological disease, autoimmune disorders and cancer. We reviewed the status quo of recent advancement of the knowledge of oncogenic role of nucleoporins in human carcinogenesis, focusing on major non-hematological malignancies in the recent literature. Both clinical study-derived and experiment-based reports were critically reviewed. We have also discussed the potential of nucleoporins as novel cancer biomarkers and promising therapeutic target against human malignancies. Several Nups such as Nup53, Nup88, Nup98, Nup160 and Nup214 modulated a plethora of cellular and physiological pathways involved in tumorigenesis such as GSK3β-Snail, Wnt/β-Catenin and RanGap1/RanBP2 signaling axes, DNA damage response, resistance to apoptosis and chemotherapy. Although classically, majority of studies have shown oncogenic roles of nucleoporins as genetic fusion partners in several types of leukemia, emerging evidence suggests that nucleoporins also modulate many cellular signaling pathways that are associated with several major non-hematological malignancies, such as carcinomas of skin, breast, lung, prostate and colon. Hence, nucleoporins are emerging as novel therapeutic targets in human tumors. Show less

CLN3 disease (Spielmeyer-Vogt-Sjogren-Batten disease) is a severe pediatric neurodegenerative disorder for which there is currently no effective treatment. The disease is characterized by progressive neuronal death, which may be triggered by abnormal intracellular calcium levels leading to neuronal apoptosis. Previously, we demonstrated reversal of the calcium effect in a neuroblastoma cell line using amlodipine and other calcium channel antagonists. In the present studies, we developed a CLN3 siRNA-inhibited primary rat neuron model to further study etoposide-induced calcium changes and apoptosis in CLN3 disease followed by recovery experiments with amlodipine. Our results show that intracellular calcium is significantly elevated in siRNA-inhibited cortical neurons after potassium chloride-induced depolarization. We were also able to show that amlodipine, a predominantly L-type dihydropyrimidine calcium channel antagonist can reverse the aberrant calcium elevations in this model of the disease. We performed an in situ TUNEL assay following etoposide-exposure to siRNA inhibited primary neurons, and apoptotic nuclei were detected providing additional evidence that increased neuronal apoptosis is associated with increased calcium levels. Amlodipine also reduced the absolute number of apoptotic cells in this experimental model. Show less

Insulin resistance associated with altered fat partitioning in liver and adipose tissues is a prediabetic condition in obese adolescents. We investigated interactions between glucose tolerance, insulin sensitivity, and the expression of lipogenic genes in abdominal subcutaneous adipose and liver tissue in 53 obese adolescents. Based on their 2-h glucose tests they were stratified in the following groups: group 1, 2-h glucose level <120 mg/dL; group 2, 2-h glucose level between 120 and 140 mg/dL; and group 3, 2-h glucose level >140 mg/dL. Liver and adipose tissue insulin sensitivity were greater in group 1 than in group 2 and group 3, and muscle insulin sensitivity progressively decreased from group 1 to group 3. The expression of the carbohydrate-responsive element-binding protein (ChREBP) was decreased in adipose tissue but increased in the liver (eight subjects) in adolescents with impaired glucose tolerance or type 2 diabetes. The expression of adipose ChREBPα and ChREBPβ was inversely related to 2-h glucose level and positively correlated to insulin sensitivity. Improvement of glucose tolerance in four subjects was associated with an increase of ChREBP/GLUT4 expression in the adipose tissue. In conclusion, early in the development of prediabetes/type 2 diabetes in youth, ChREBPβ expression in adipose tissue predicts insulin resistance and, therefore, might play a role in the regulation of glucose tolerance. Show less

Proteins involved in mitochondrial metabolic pathways engage in functionally relevant multi-enzyme complexes. We previously described an interaction between short-chain 3-hydroxyacyl-coenzyme A dehydrogenase (SCHAD) and glutamate dehydrogenase (GDH) explaining the clinical phenotype of hyperinsulinism in SCHAD-deficient patients and adding SCHAD to the list of mitochondrial proteins capable of forming functional, multi-pathway complexes. In this work, we provide evidence of SCHAD's involvement in additional interactions forming tissue-specific metabolic super complexes involving both membrane-associated and matrix-dwelling enzymes and spanning multiple metabolic pathways. As an example, in murine liver, we find SCHAD interaction with aspartate transaminase (AST) and GDH from amino acid metabolic pathways, carbamoyl phosphate synthase I (CPS-1) from ureagenesis, other fatty acid oxidation and ketogenesis enzymes and fructose-bisphosphate aldolase, an extra-mitochondrial enzyme of the glycolytic pathway. Most of the interactions appear to be independent of SCHAD's role in the penultimate step of fatty acid oxidation suggesting an organizational, structural or non-enzymatic role for the SCHAD protein. Show less

Defects of the CLN3 gene on chromosome 16p12.1 lead to the juvenile form of neuronal ceroid-lipofuscinosis (JNCL, Batten Disease), the most common recessive inherited neurodegenerative disorder in children. Dysregulation of intracellular calcium homeostasis in the absence of a functional CLN3 protein (CLN3P, Battenin) has been linked to synaptic dysfunction and accelerated apoptosis in vulnerable neuronal cells. Prolonged increase of intracellular calcium concentration is considered to be a significant trigger for neuronal apoptosis and cellular loss in JNCL. We examined the potential effect of 41 different calcium channel modulators on intracellular calcium concentration in CLN3 siRNA knock down SH-SY5Y neuroblastoma cells. Six drugs belonging to the group of voltage dependent L-type channel blockers show significant lowering of the increased intracellular calcium levels in CLN3 siRNA knock down cells. Our studies provide important new data suggesting possible beneficial effects of the tested drugs on calcium flux regulated pathways in neuronal cell death. Therapeutic intervention in this untreatable disease will likely require drugs that cross the blood-brain barrier as did all of the positively screened drugs in this study. Better comprehension of the mechanism of neurodegeneration in rare recessive disorders, such as neuronal ceroid-lipofuscinoses, is likely to help to better understand mechanisms involved in more complex genetic neurodegenerative conditions, such as those associated with aging. Show less

We recently demonstrated reduced activity of a novel palmitoyl-protein Delta-9 desaturase in neuronal tissues from mice with the cln3 Juvenile Neuronal Ceroid-Lipofuscinosis (Batten disease) gene ablated. In this follow-up study we have been able to obtain tissues from heterozygous cln3 mice and report that the enzyme activity in brain and pancreas from the heterozygotes is intermediate at 40% of the wild-type activity and consistent with recessive inheritance. Neuronal tissues from the CLN1 knock-out mouse demonstrated normal enzymatic activity pointing to the specificity of the desaturase function to CLN3. Non-neuronal tissues did not have measurable desaturase activity in wild-type or knock-out mice using this assay system. This may be due to lack of sensitivity of our assay system in these tissues or failure to activate the enzyme in these tissues. This is the first report of a heterozygous abnormality in Batten disease and provides important confirmation that this is the function of the CLN3 protein in neuronal tissues. Show less

Juvenile neuronal ceroid-lipofuscinosis (JNCL, Batten disease, Spielmeyer-Vogt-Sjogren disease, CLN3) is the most common inherited, autosomal recessive, neurodegenerative disorder in man. Like the other neuronal ceroid-lipofuscinoses, it is characterized by progressive loss of vision, seizures, and loss of cognitive and motor functions, leading to premature demise. JNCL is caused by mutations of CLN3, a gene that encodes a hydrophobic transmembrane protein, which localizes to membrane lipid rafts in lysosomes, endosomes, synaptosomes, and cell membrane. While the primary function of the CLN3 protein (CLN3P) may be debated, its absence affects numerous cellular functions including pH regulation, arginine transport, membrane trafficking, and apoptosis. We have recently suggested that the unifying primary function of CLN3P may be in a novel palmitoyl-protein Delta-9 desaturase (PPD) activity that in our opinion could explain all of the various functional abnormalities seen in the JNCL cells. Another group of researchers has recently shown a correlation between the CLN3P expression and the synthesis of bis(monoacylglycerol)phosphate (BMP) and suggested that CLN3P may play a role in the biosynthesis of BMP. In this review, following an introduction to the neuronal ceroid-lipofuscinoses, we provide a brief overview and an update of the most recent research in JNCL, specifically that related to the function of CLN3P. Show less

Batten's disease, one of the most common recessively inherited, untreatable, neurodegenerative diseases of humans, is characterized by progressive neuronal loss and intraneuronal proteolipid storage. Although the gene for the disorder was cloned more than a decade ago, the function of the encoded protein, CLN3P, has not been defined thus far. Sequence analysis using the Pfam server identified a low stringency match to a fatty acid desaturase domain in the N-terminal sequence of CLN3P. We developed a fatty acid desaturase assay based on measurement of desaturase products by gas chromatography/mass spectrometry. We show that CLN3P is a novel palmitoyl-protein Delta-9 desaturase, which converts membrane-associated palmitoylated proteins to their respective palmitoleated derivatives. We have further demonstrated that this palmitoyl-protein Delta-9 desaturase activity is deficient in cln3(-/-) mouse pancreas and is completely ablated in neuroblastoma cells by RNA inhibition. We propose that palmitoyl-protein desaturation defines a new mechanism of proteolipid modification, and that deficiency of this process leads to the signs and symptoms of Batten's disease. Show less

Juvenile neuronal ceroid-lipofuscinosis (JNCL) or Batten/Spielmeyer-Vogt-Sjogren disease (OMIM #204200) is one of a group of nine clinically related inherited neurodegenerative disorders (CLN1-9). JNCL results from mutations in CLN3 on chromosome 16p12.1. The neuronal loss in Batten disease has been shown to be due to a combination of apoptosis and autophagy suggesting that CLN3P, the defective protein, may have an anti-neuronal death function. PANDER (PANcreatic-DERived factor) is a novel cytokine that was recently cloned from pancreatic islet cells. PANDER is specifically expressed in the pancreatic islets, small intestine, testis, prostate, and neurons of the central nervous system, and has been demonstrated to induce apoptosis. In this study, we over-expressed CLN3P in SH-SY5Y neuroblastoma cells and monitored the effects on PANDER-induced apoptosis. CLN3P significantly increased the survival rate of the SH-SY5Y cells in this system. This study provides additional evidence that the function of CLN3P is related to preventing neuronal apoptosis. Show less

Batten disease is a severe autosomal recessive neurodegenerative disease which results from mutations in CLN3. Although the gene was cloned in 1995, the tissue distribution and subcellular localization of the CLN3 protein (CLN3P) remains inconclusive. We have demonstrated the presence of a novel 33 kDa protein in both normal human and wild-type mouse brain. This 33 kDa protein, which is overexpressed in brains of patients with Batten disease and in Cln3-/- mouse brain, binds to the antibody raised against the peptide sequence of CLN3P and results in aberrant CLN3P localization studies. We expressed a novel 33 kDa protein that is highly similar to CLN3P. We showed that the 33 kDa protein is identical to that recognized in Batten disease and Cln3-/- brain. These studies strongly suggest the presence of an alternative CLN3-like (CLN3L) product in Batten disease. Previous studies of CLN3P tissue distribution and intracellular localization will require extensive reanalysis in order to determine the true expression of CLN3P. Show less

Juvenile neuronal ceroid lipofuscinosis is an inherited pediatric neurodegenerative disorder, which occurs as a result of mutations in the CLN3 gene that is located on chromosome 16p12.1. The encoded protein, CLN3P, is a putative transmembrane protein with no known function. In this study, we demonstrate that CLN3P resides on membrane lipid raft domains (detergent-resistant membranes) and provide important new data towards possible functions of the protein. Show less