Integrative Analyses of Tumor and Peripheral Biomarkers in the Treatment of Advanced Renal Cell Carcinoma

The phase III JAVELIN Renal 101 trial demonstrated prolonged progression-free survival (PFS) in patients (N = 886) with advanced renal cell carcinoma treated with first-line avelumab + axitinib (A+Ax) versus sunitinib. We report novel findings from integrated analyses of longitudinal blood samples and baseline tumor tissue. PFS was associated with elevated lymphocyte levels in the sunitinib arm and an abundance of innate immune subsets in the A+Ax arm. Treatment with A+Ax led to greater T-cell repertoire modulation and less change in T-cell numbers versus sunitinib. In the A+Ax arm, patients with tumors harboring mutations in ≥2 of 10 previously identified PFS-associated genes (double mutants) had distinct circulating and tumor-infiltrating immunologic profiles versus those with wild-type or single-mutant tumors, suggesting a role for non-T-cell-mediated and non-natural killer cell-mediated mechanisms in double-mutant tumors. We provide evidence for different immunomodulatory mechanisms based on treatment (A+Ax vs. sunitinib) and tumor molecular subtypes.

SIGNIFICANCE

Our findings provide novel insights into the different immunomodulatory mechanisms governing responses in patients treated with avelumab (PD-L1 inhibitor) + axitinib or sunitinib (both VEGF inhibitors), highlighting the contribution of tumor biology to the complexity of the roles and interactions of infiltrating immune cells in response to these treatment regimens. This article is featured in Selected Articles from This Issue, p. 384.

Plain language summary looking at how long side effects last after treatment with axitinib is stopped in people with advanced renal cell carcinoma

Axitinib is a medication that stops cancer cell growth by depriving the cancer cell of the nutrients and oxygen that it needs. Axitinib is used to treat advanced renal cell carcinoma (RCC), which is a type of kidney cancer that has spread within or beyond the kidney. Axitinib has been approved for the treatment of RCC as either a first treatment option or a second treatment option. It is used as a first treatment option for RCC when combined with a medication that reactivates the immune system (immunotherapy), either avelumab or pembrolizumab. If the advanced RCC starts growing again it can be used as a second treatment option where it is taken by itself. It is essential to conduct studies to assess how well the drug works and whether it has any side effects in order to understand whether it is safe to give to people. This summary reports the combined results of 5 studies and looks at how long side effects last after treatment is temporarily stopped. Researchers found that side effects generally got better in 3 days or less after people stopped taking axitinib on its own. The time it took for side effects to get better was generally shorter than for other similar drugs or combinations of axitinib and immunotherapy. The results of individual studies may vary from these 5 combined study results. Three of the 5 studies were ongoing at the time of this analysis and the final outcomes of those studies may differ from those described in this summary. The purpose of this plain language summary is to help you understand the findings from recent research. Health professionals should make treatment decisions based on all available evidence. Clinical Trial Registration: NCT00678392, NCT00920816, NCT02493751, NCT02684006, NCT02853331 (ClinicalTrials.gov).

Activator protein 2 alpha (AP2alpha) suppresses 42 kDa C/CAAT enhancer binding protein alpha (p42(C/EBPalpha)) in head and neck squamous cell carcinoma

The tumor suppressor C/CAAT enhancer binding protein alpha (C/EBPalpha) is a transcription factor involved in cell cycle control and cellular differentiation. A recent study showed that C/EBPalpha is frequently downregulated in head and neck squamous cell carcinoma (HNSCC) by DNA methylation in an upstream regulatory region. Here, we investigated how DNA methylation in the upstream regulatory region disrupts the transcriptional regulation of C/EBPalpha in HNSCC. The results reveal that aberrant methylation correlates with methyl binding domain protein binding and repressive histone modifications. This methylated region contains previously uninvestigated AP2alpha binding sites. AP2alpha suppresses C/EBPalpha promoter activity and protein expression. Interestingly, silencing AP2alpha by shRNA increases the antiproliferative isoform of C/EBPalpha (p42(C/EBPalpha)). Furthermore, growth analysis revealed that these 2 isoforms yield very different proliferative properties in HNSCC.

Regulation of the PTEN promoter by statins and SREBP

Germline mutations in the tumor-suppressor gene PTEN predispose to heritable breast cancer. The transcription factor peroxisome proliferator-activated receptor-gamma (PPARgamma) has also been implicated as a tumor suppressor pertinent to a range of neoplasias, including breast cancer. We previously demonstrated that lovastatin may signal through PPARgamma and directly upregulate PTEN expression at the transcriptional level. In our current study, we show that simvastatin, pravastatin and fluvastatin can induce PTEN expression in a dose-dependent manner. This resulted from an increase in PTEN mRNA indicating transcriptional upregulation. In addition, we observed, for the first time, that upregulation of sterol response element-binding protein (SREBP), known to induce PPARgamma expression, can increase PTEN expression. Using reporter assays, we observed that both the statins and SREBP could specifically induce PPARgamma-mediated transcription. However, the statins do not appear to signal through SREBP. Furthermore, our results indicate that SREBP utilizes PPARgamma's transcriptional activity to induce PTEN transcription, whereas the statins signal through PPARgamma's protein activity to upregulate PTEN expression. Overall, our observations suggest that statins signal through another transcription factor, in a PPARgamma-dependent manner, which in turn induces PTEN transcription. We, therefore, studied the full-length PTEN promoter through serial deletion reporter assays and electromobility shift assays and identified a region between -854 and -791 that binds an as-yet-unidentified transcription factor, through which the statins induce PTEN expression. Since PTEN is constitutively active, our data indicate it may be worthwhile to examine statin and SREBP stimulation as mechanisms to increase PTEN expression for therapeutic and preventative strategies in cancer, diabetes mellitus and cardiovascular disease.

Cowden syndrome-affected patients with PTEN promoter mutations demonstrate abnormal protein translation

Germline mutations of PTEN (phosphatase and tensin homolog deleted on chromosome 10) are associated with the multihamartomatous disorder Cowden syndrome (CS). Moreover, patients with CS with germline PTEN promoter mutations have aberrant PTEN protein expression and an increased frequency of breast cancer. Here, we examined the downstream effect of five PTEN promoter variants (-861G/T, -853C/G, -834C/T, -798G/C, and -764G/A) that are not within any known cis-acting regulatory elements. Clinically, all five of these patients have been given diagnoses of breast, thyroid, and/or endometrial cancer. We demonstrated that protein binding to the PTEN promoter (-893 to -755) was not altered in the five variants when compared with the wild-type (WT) promoter. However, reporter assays indicated that three of the variants (-861G/T, -853C/G, and -764G/A) demonstrated an ~50% decrease in luciferase activity compared with the WT construct. PTEN messenger RNA (mRNA) levels were not altered in these variants, whereas secondary structure predictions indicated that different PTEN 5' untranslated region transcript-folding patterns exist in three variants, suggesting an inhibition of protein translation. This was confirmed by PTEN protein analysis. These data indicate that variants causing large mRNA secondary structure alterations result in an inhibition of protein translation and a decrease in PTEN protein expression. These data emphasize the importance of PTEN promoter nucleotide variations and their ability to lead to CS progression by a novel regulatory mechanism. Importantly, these patients have a high prevalence of breast, thyroid, and endometrial malignancies; thus, understanding of the mechanism of PTEN dysfunction in these patients will lead to more-sensitive molecular diagnostic and predictive testing and, ultimately, to rational targeted therapies to treat or prevent malignancy.

A limited set of human MicroRNA is deregulated in follicular thyroid carcinoma

CONTEXT

Although the pathogenesis of follicular thyroid carcinoma (FTC) and its relation to follicular adenoma (FA) remains unclear, detailed understanding of FTC carcinogenesis would facilitate addressing the scientific and clinical challenges, given that there are morphological and molecular similarities between FTC and the frequently occurring FA. Micro-RNAs (miRNAs) are a new class of small, noncoding RNAs implicated in development and cancer and may lend novel clues to FTC genesis. For the latter process, a deregulated miRNA can orchestrate the aberrant expression of several hundred target genes.

OBJECTIVE

The objective of the study was to identify deregulated miRNAs in FTC.

DESIGN

We used two high-density expression arrays to identify miRNAs and their target genes that are differentially expressed between FTC and FA. Validation was done by quantitative RT-PCR. We further functionally characterized the effect of deregulated miRNAs in vitro using HEK293T, FTC133, and K5 cell lines.

PATIENTS

In total, 45 primary thyroid samples (23 FTC, 20 FA, four normal control thyroid) were analyzed.

RESULTS

Two specific miRNAs, miR-197 and miR-346, were significantly overexpressed in FTC. In vitro overexpression of either miRNA induced proliferation, whereas inhibition led to growth arrest. Overexpression of miR-197 and miR-346 repressed the expression of their predicted target genes in vitro and in vivo.

CONCLUSIONS

Our observations show that miR-197 and miR-346 contribute to FTC carcinogenesis. Both miRNAs and their target genes might potentially provide for novel molecular markers and act as novel targets for treatment by interference, which could potentially normalize the deregulated profile of many downstream target genes.

Increased PTEN expression due to transcriptional activation of PPARgamma by Lovastatin and Rosiglitazone

Germline mutations in the tumor suppressor gene PTEN (protein phosphatase and tensin homolog located on chromosome ten) predispose to heritable breast cancer. The transcription factor PPARgamma has also been implicated as a tumor suppressor pertinent to a range of neoplasias, including breast cancer. A putative PPARgamma binding site in the PTEN promoter indicates that PPARgamma may regulate PTEN expression. We show here that the PPARgamma agonist Rosiglitazone, along with Lovastatin, induce PTEN in a dose- and time-dependent manner. Lovastatin- or Rosiglitazone-induced PTEN expression was accompanied by a decrease in phosphorylated-AKT and phosphorylated-MAPK and an increase in G1 arrest. We demonstrate that the mechanism of Lovastatin- and Rosiglitazone-associated PTEN expression was a result of an increase in PTEN mRNA, suggesting that this increase was transcriptionally-mediated. Compound-66, an inactive form of Rosiglitazone, which is incapable of activating PPARgamma, was unable to elicit the same response as Rosiglitazone, signifying that the Rosiglitazone response is PPARgamma-mediated. To support this, we show, using reporter assays including dominant-negative constructs of PPARgamma, that both Lovastatin and Rosiglitazone specifically mediate PPARgamma activation. Additionally, we demonstrated that cells lacking PTEN or PPARgamma were unable to induce PTEN mediated cellular events in the presence of Lovastatin or Rosiglitazone. These data are the first to demonstrate that Lovastatin can signal through PPARgamma and directly demonstrate that PPARgamma can upregulate PTEN at the transcriptional level. Since PTEN is constitutively active, our data indicates it may be worthwhile to examine Rosiglitazone and Lovastatin stimulation as mechanisms to increase PTEN expression for therapeutic and preventative strategies including cancer, diabetes mellitus and cardiovascular disease.