Search

Background Vitamin D3 (VitD) deficiency is linked to increased incidence and worse survival in bladder cancer (BCa). In addition to cystectomy, patients are treated with cisplatin-based chemotherapy, however 30%-50% of patients do not benefit from this treatment. The effects of VitD deficiency on response to chemotherapy remain unknown. Methods To test effects of VitD supplementation on the response to cisplatin we analyzed patient serum VitD levels and correlated that with survival. In vivo, VitD deficient mice were treated with cisplatin, with or without pretreatment with the active VitD metabolite, 1,25 dihydroxyvitamin D3 (1,25D3 ). Lastly, using BCa cell lines, T24 and RT-112, the mechanism of action of 1,25D3 and cisplatin combination treatment was determined by apoptosis assays, as well as western blot and RT-PCR. Results In this study, we determined that low serum 25 hydroxyvitamin D3 (25D3 ) levels was significantly associated with worse response to cisplatin. Pretreating deficient mice with 1,25D3 , reduced tumor volume compared to cisplatin monotherapy. In vitro, 1,25D3 pretreatment increased the apoptotic response to cisplatin. 1,25D3 pretreatment increased expression of TAp73 and its pro-apoptotic targets, in a VDR dependent manner. VDR and its transcriptional targets were induced after 1,25D3 treatment and further increased after the combination of 1,25D3 and cisplatin in a TAp73 dependent manner. Conclusions Our data suggest that VitD deficiency could be a biomarker for poor response to cisplatin, and pretreating with VitD can increase the apoptotic response to cisplatin through VDR and TAp73 signaling crosstalk.

The anticancer activity of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3 or calcitriol) has been widely reported in preclinical models. However, systematic investigation into the chemopreventive potential of calcitriol against the spectrum of oral carcinogenesis has not been performed. To address this gap in knowledge, we conducted a preclinical prevention trial of calcitriol in the 4-nitroquinoline-1-oxide (4NQO) oral carcinogenesis model. C57BL/6 mice were exposed to the carcinogen 4NQO in drinking water for 16 weeks and randomized to control (4NQO only) or calcitriol arms. Calcitriol (0.1 μg i.p, Monday, Wednesday, and Friday) was administered for (i) 16 weeks concurrently with 4NQO exposure, (ii) 10 weeks post completion of 4NQO exposure, and, (iii) a period of 26 weeks concurrent with and following 4NQO exposure. Longitudinal magnetic resonance imaging (MRI) was performed to monitor disease progression until end point (week 26). Correlative histopathology of tongue sections was performed to determine incidence and multiplicity of oral dysplastic lesions and squamous cell carcinomas (SCC). Vitamin D metabolites and calcium were measured in the serum using liquid chromatography-mass spectrometry (LC–MS/MS) and colorimetric assay, respectively. Renal CYP24A1 (24-hydroxylase) and CYP27B1 (1α-hydroxylase) expression was measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Immunostaining of tongue sections for vitamin D receptor (VDR), CYP24A1, and Ki67 was also performed. Non-invasive MRI enabled longitudinal assessment of lesions in the oral cavity. Calcitriol administered concurrently with 4NQO for 16 weeks significantly (P

EGFR tyrosine kinase inhibitors (EGFR TKIs) are the standard of care treatment for patients with EGFR-mutant lung adenocarcinoma (LUAD). Although initially effective, EGFR TKIs are not curative. Disease inevitably relapses due to acquired drug resistance. We hypothesized that vitamin D metabolites could be used with EGFR TKIs to prevent therapeutic failure. To test this idea, we investigated the link between serum 25-hydroxyvitamin D3 (25(OH)D3) and progression-free survival (PFS) in patients with EGFR-mutant LUAD that received EGFR TKIs (erlotinib n = 20 and afatinib n = 1). Patients who were 25(OH)D3-sufficient experienced significantly longer benefit from EGFR TKI therapy (mean 14.5 months) than those with 25(OH)D3 insufficiency (mean 10.6 months, p = 0.026). In contrast, 25(OH)D3 had no prognostic value in patients with KRAS-mutant LUAD that received cytotoxic chemotherapy. To gain mechanistic insights, we tested 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) activity in vitro. 1,25(OH)2D3 promoted epithelial differentiation and restored EGFR TKI sensitivity in models of EGFR TKI resistance that were associated with epithelial&ndash, mesenchymal transition (EMT). 1,25(OH)2D3 was ineffective in a non-EMT model of resistance. We conclude that vitamin D sufficiency portends increased PFS among EGFR-mutant LUAD patients that receive EGFR TKIs, and that vitamin D signaling maintains drug efficacy in this specific patient subset by opposing EMT.

Somatic alterations in the epidermal growth factor receptor gene (EGFR) result in aberrant activation of kinase signaling and occur in ∼15% of non-small cell lung cancers (NSCLC). Patients diagnosed with EGFR-mutant NSCLC have good initial clinical response to EGFR tyrosine kinase inhibitors (EGFR TKIs), yet tumor recurrence is common and quick to develop. Mechanisms of acquired resistance to EGFR TKIs have been studied extensively over the past decade. Great progress has been made in understanding two major routes of therapeutic failure: additional genomic alterations in the EGFR gene and activation of alternative kinase signaling (so-called “bypass activation”). Several pharmacological agents aimed at overcoming these modes of EGFR TKI resistance are FDA-approved or under clinical development. Phenotypic transformation, a less common and less well understood mechanism of EGFR TKI resistance is yet to be addressed in the clinic. In the context of acquired EGFR TKI resistance, phenotypic transformation encompasses epithelial to mesenchymal transition (EMT), transformation of adenocarcinoma of the lung (LUAD) to squamous cell carcinoma (SCC) or small cell lung cancer (SCLC). SCLC transformation, or neuroendocrine differentiation, has been linked to inactivation of TP53 and RB1 signaling. However, the exact mechanism that permits lineage switching needs further investigation. Recent reports indicate that LUAD and SCLC have a common cell of origin, and that trans-differentiation occurs under the right conditions. Options for therapeutic targeting of EGFR-mutant SCLC are limited currently to conventional genotoxic chemotherapy. Similarly, the basis of EMT-associated resistance is not clear. EMT is a complex process that can be characterized by a spectrum of intermediate states with diverse expression of epithelial and mesenchymal factors. In the context of acquired resistance to EGFR TKIs, EMT frequently co-occurs with bypass activation, making it challenging to determine the exact contribution of EMT to therapeutic failure. Reversibility of EMT-associated resistance points toward its epigenetic origin, with additional adjustments, such as genetic alterations and bypass activation, occurring later during disease progression. This review will discuss the mechanistic basis for EGFR TKI resistance linked to phenotypic transformation, as well as challenges and opportunities in addressing this type of targeted therapy resistance in EGFR-mutant NSCLC.

Recent studies highlight the importance of the RB1 tumor suppressor as a target for cancer therapy. Canonically, RB1 regulates cell cycle progression and represents the downstream target for cyclin-dependent kinase (CDK) 4/6 inhibitors that are in clinical use. However, newly discovered features of the RB1 pathway suggest new therapeutic strategies to counter resistance and improve precision medicine. These therapeutic strategies include deepening cell cycle exit with CDK4/6 inhibitor combinations, selectively targeting tumors that have lost RB1, and expanding therapeutic index by mitigating therapy-associated adverse effects. In addition, RB1 impacts immunological features of tumors and the microenvironment that can enhance sensitivity to immunotherapy. Lastly, RB1 specifies epigenetically determined cell lineage states that are disrupted during therapy resistance and could be re-installed through the direct use of epigenetic therapies. Thus, new opportunities are emerging to improve cancer therapy by exploiting the RB1 pathway.

1,25-dihydroxyvitamin D3 (1,25(OH)2D3) exerts anti-proliferative activity by binding to the vitamin D receptor (VDR) and regulating gene expression. We previously reported that non-small cell lung cancer (NSCLC) cells which harbor epidermal growth factor receptor (EGFR) mutations display elevated VDR expression (VDRhigh) and are vitamin D-sensitive. Conversely, those with K-ras mutations are VDRlow and vitamin D-refractory. Because EGFR mutations are found predominately in NSCLC cells with an epithelial phenotype and K-ras mutations are more common in cells with a mesenchymal phenotype, we investigated the relationship between vitamin D signaling capacity and the epithelial mesenchymal transition (EMT). Using NSCLC cell lines and publically available lung cancer cell line microarray data, we identified a relationship between VDR expression, 1,25(OH)2D3 sensitivity, and EMT phenotype. Further, we discovered that 1,25(OH)2D3 induces E-cadherin and decreases EMT-related molecules SNAIL, ZEB1, and vimentin in NSCLC cells. 1,25(OH)2D3-mediated changes in gene expression are associated with a significant decrease in cell migration and maintenance of epithelial morphology. These data indicate that 1,25(OH)2D3 opposes EMT in NSCLC cells. Because EMT is associated with increased migration, invasion, and chemoresistance, our data imply that 1,25(OH)2D3 may prevent lung cancer progression in a molecularly defined subset of NSCLC patients.

Ligand structure can affect the activation of nuclear receptors, such as estrogen receptors (ERs), and their control of signaling pathways for cellular responses including death and differentiation. We hypothesized that distinct biological functions of similar estradiol (E2) analogs could be identified by integrating gene expression patterns obtained from human tumor cell lines with receptor binding and functional data for the purpose of developing compounds for treatment of a variety of diseases. We compared the estrogen receptor subtype selectivity and impact on signaling pathways for three distinct, but structurally similar, analogs of E2. Modifications in the core structure of E2led to pronounced changes in subtype selectivity for estrogen receptors, ER-α or ER-β, along with varying degrees of ER dimerization and activation. While all three E2analogs are predominantly ER-β agonists, the cell growth inhibitory activity commonly associated with this class of compounds was detected for only two of the analogs and might be explained by a ligand-specific pattern of gene transcription. Microarray studies using three different human tumor cell lines demonstrated that the analogs distinctly affect the transcription of genes in signaling pathways for chromosome replication, cell death, and oligodendrocyte progenitor cell differentiation. That the E2analogs could lower tumor cell viability and stimulate neuronal differentiation confirmed that gene expression data could accurately distinguish biological activity of the E2analogs. The findings reported here confirm that cellular responses can be regulated by making key structural alterations to the core structure of endogenous ER ligands.

Lung cancer has long been thought of as a cancer that mainly affects men, but over the past several decades, because of the high increase in tobacco use by women, there has been a corresponding dramatic increase in lung cancer among women. Since 1998, lung cancer deaths in women have surpassed those caused by breast cancer in the United States. Annual lung cancer deaths among US women currently surpass those caused by breast, ovarian, and cervical cancers combined. Women are more likely than men to be diagnosed with adenocarcinoma and small cell carcinoma of the lung compared to squamous cell carcinoma, and never-smokers diagnosed with lung cancer are almost three times more likely to be female than male. These observations in the population, coupled to the findings that both estrogen receptors (ERs) and aromatase, the enzyme that synthesizes 17beta-estradiol, are expressed by lung tumors, suggest a role for female steroid hormones in control of lung cancer growth. Preclinical data and clinical data are increasingly emerging to support this concept, and to suggest that a local production of estrogen and expression of ERs occurs in lung tumors that arise in men as well as in women. An additional protein that recognizes 17beta-estradiol with high affinity, GPR30, also is expressed in lung tumors at high levels and may be responsible for some of the proliferation signals induced by estrogen.