Loris Bertazza

Tumor necrosis factor (TNF) biology and cell death

Tumor necrosis factor (TNF) was the first cytokine to be used in humans for cancer therapy. However, its role in the treatment of cancer patients is debated. Most uncertainties in this field stem from the knowledge that the pathways directly activated or indirectly affected upon TNF engagement with its receptors can ultimately lead to very different outcomes in terms of cell survival. In this article, we summarize the fundamental molecular biology aspects of this cytokine. Such a basis is a prerequisite to critically approach the sometimes conflicting preclinical and clinical findings regarding the relationship between TNF, tumor biology and anticancer therapy. Although the last decade has witnessed remarkable advances in this field, we still do not know in detail how cells choose between life and death after TNF stimulation. Understanding this mechanism will not only shed new light on the physiological significance of TNF-driven programmed cell death but also help investigators maximize the anticancer potential of this cytokine.

The Dual Role of Tumor Necrosis Factor (TNF) in Cancer Biology

Tumor necrosis factor (TNF) is a cytokine with well known anticancer properties and is being utilized as anticancer agent for the treatment of patients with locally advanced solid tumors. However, TNF role in cancer biology is debated. In fact, in spite of the wealth of evidence supporting its antitumor activity, the cascade of molecular events underlying TNF-mediated tumor regression observed in vivo is still incompletely elucidated. Furthermore, some preclinical findings suggest that TNF may even promote cancer development and progression. With this work we intend to summarize the molecular biology of TNF (with particular regard to its tumor-related activities) and review the experimental and clinical evidence currently available describing the complex and sometime apparently conflicting relationship between this cytokine, cancer biology and antitumor therapy. We also propose a model to explain the dual effect of TNF based on the exposure time and cytokine levels reached within the tumor microenvironment. Finally, we overview recent research findings that might lead to new ways for exploiting the anticancer potential of TNF in the clinical setting.

The PDCD4/miR-21 pathway in medullary thyroid carcinoma.

Programmed cell death 4 (PDCD4) is a tumor suppressor gene involved in tumorogenesis. MicroRNA-21 (miR-21) specifically targets PDCD4, and recent studies suggest that PDCD4 is also regulated by Akt (antiapoptotic regulator within phosphatidylinositol 3-kinase). Medullary thyroid carcinoma (MTC) is a rare neuroendocrine cancer, and disease stage at diagnosis represents the main prognostic indicator. A consecutive series of 64 MTCs was considered. REarranged during Transfection (RET) and rat sarcoma (RAS) mutation status was assessed by direct sequencing. Quantitative real-time polymerase chain reaction was used to quantify mature hsa-miR-21. PDCD4 and Ki-67 immunostaining was performed with an automated platform. Immunoblot analysis of PI3K/Akt pathway was done on thyroid tissues. MTCs were consistently associated with miR-21 up-regulation (P < .0016) and featured significant PDCD4 nuclear down-regulation. An inverse correlation emerged between miR-21 overexpression and PDCD4 down-regulation (P = .0013). At enrollment, high miR-21 levels were associated with high calcitonin levels (P = .0003), lymph node metastases (P = .001), and advanced stages (P = .0003). At the end of follow-up, high miR-21 levels were associated with biochemically persistent disease (P = .0076). At enrollment, instead, PDCD4 nuclear down-regulation was associated with high calcitonin levels (P = .04), more advanced stages of disease (P < .01), and persistent disease after the follow-up (P = .02). p-Akt was more expressed in RAS-mutated MTC than in nonmutated cancers and normal tissue. This study showed, in MTCs, that miR-21 regulates PDCD4 expression and also that the miR-21/PDCD4 pathway correlates with clinicopathological variables and prognosis. Further studies should investigate the role of miR-21 as a prognostic biomarker and the feasibility of using PDCD4-restoring strategies as a therapeutic approach to MTC.

Overexpression of L-Type amino acid transporter 1 (LAT1) and 2 (LAT2): Novel markers of neuroendocrine tumors

Background 6-18F-fluoro-L-3,4-dihydroxyphenylalanine (18F-FDOPA) PET is a useful tool in the clinical management of pheochromocytoma (PHEO) and medullary thyroid carcinoma (MTC). 18F-FDOPA is a large neutral amino acid biochemically resembling endogenous L-DOPA and taken up by the L-type amino acid transporters (LAT1 and LAT2). This study was conducted to examine the expression of the LAT system in PHEO and MTC. Methods Real-time PCR and Western blot analyses were used to assess LAT1 and LAT2 gene and protein expression in 32 PHEO, 38 MTC, 16 normal adrenal medulla and 15 normal thyroid tissue samples. Immunohistochemistry method was applied to identify the proteins’ subcellular localization. Results LAT1 and LAT2 were overexpressed in both PHEO and MTC by comparison with normal tissues. LAT1 presented a stronger induction than LAT2, and their greater expression was more evident in PHEO (15.1- and 4.1-fold increases, respectively) than in MTC (9.9- and 4.1-fold increases, respectively). Furthermore we found a good correlation between LAT1/2 and GLUT1 expression levels. A positive correlation was also found between urinary noradrenaline and adrenaline levels and LAT1 gene expression in PHEO. The increased expression of LAT1 is also confirmed at the protein level, in both PHEO and MTC, with a strong cytoplasmic localization. Conclusions The present study is the first to provide experimental evidence of the overexpression in some NET cancers (such as PHEO or MTC) of L-type amino acid transporters, and the LAT1 isoform in particular, giving the molecular basis to explain the increase of the DOPA uptake seen in such tumor cells.

Calcitonin measurement and immunoassay interference: a case report and literature review

Abstract Calcitonin (CT) is currently the most sensitive serological marker of C-cell disease [medullary thyroid carcinoma (MTC) and C-cell hyperplasia]. Starting with a report on a case that occurred at our institution, this review focuses on trying to explain the reasons behind the poor specificity and sensitivity of the various CT immunoassays. A 15-year-old patient was referred to our institution in May 2014 for moderately elevated CT levels. Thyroid ultrasonography (US) documented a colloidal goiter. Secondary causes of the hypercalcitoninemia (hyperCT) were ruled out. The mismatch between the clinical picture and the laboratory results prompted us to search for other reasons for the patient’s high CT levels, so we applied the heterophilic blocking tube (HBT) procedure to the patient’s sera before the CT assay. Using this pretreatment step, his serum CT concentration dropped to <1 ng/L, as measured at the same laboratory. Measuring plasma CT has an important role in screening for C-cell disease, but moderately elevated serum CT levels need to be placed in their clinical context, bearing in mind all the secondary causes of C-cell hyperplasia and the possibility of laboratory interference, before exposing patients to the risks and costs of further tests.

Circumventing melanoma chemoresistance by targeting DNA repair.

Available evidence demonstrates that the DNA repair machinery is involved in melanoma resistance to chemotherapeutics. Furhtermore, preclinical findings suggest that interfering with DNA repair could increase chemosensitivity of melanoma cells. However, the clinical implementation of these principles is still in its infancy and no such strategy is currently proven to be effective in patients with advanced melanoma. Since the molecular mechanisms governing the relationship between chemoresistance and DNA repair are not fully elucidated, more basic and translational research is needed to understand the reasons for the failures and to identify novel targets. In this review we summarize the experimental and clinical findings that are fostering the research in this promising field of oncology.

The aurora kinase inhibitor VX-680 shows anti-cancer effects in primary metastatic cells and the SW13 cell line

New therapeutic targets are needed to fight cancer. Aurora kinases (AK) were recently identified as vital key regulators of cell mitosis and have consequently been investigated as therapeutic targets in preclinical and clinical studies. Aurora kinase inhibitors (AKI) have been studied in many cancer types, but their potential capacity to limit or delay metastases has rarely been considered, and never in adrenal tissue. Given the lack of an effective pharmacological therapy for adrenal metastasis and adrenocortical carcinoma, we assessed AKI (VX-680, SNS314, ZM447439) in 2 cell lines (H295R and SW13 cells), 3 cell cultures of primary adrenocortical metastases (from lung cancer), and 4 primary adrenocortical tumor cell cultures. We also tested reversan, which is a P-gp inhibitor (a fundamental efflux pump that can extrude drugs), and we measured AK expression levels in 66 adrenocortical tumor tissue samples. Biomolecular and cellular tests were performed (such as MTT, thymidine assay, Wright’s staining, cell cycle and apoptosis analysis, Western blot, qRT-PCR, and mutation analysis). Our results are the first to document AK overexpression in adrenocortical carcinoma as well as in H295R and SW13 cell lines, thus proving the efficacy of AKI against adrenal metastases and in the SW13 cancer cell model. We also demonstrated that reversan and AKI Vx-680 are useless in the H295R cell model, and therefore should not be considered as potential treatments for ACC. Serine/threonine AK inhibition, essentially with VX-680, could be a promising, specific therapeutic tool for eradicating metastases in adrenocortical tissue.

A constitutive active MAPK/ERK pathway due to BRAFV600E positively regulates AHR pathway in PTC.

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor mediating the toxicity and tumor-promoting properties of dioxin. AHR has been reported to be overexpressed and constitutively active in a variety of solid tumors, but few data are currently available concerning its role in thyroid cancer. In this study we quantitatively explored a series of 51 paired-normal and papillary thyroid carcinoma (PTC) tissues for AHR-related genes. We identified an increased AHR expression/activity in PTC, independently from its nuclear dimerization partner and repressor but strictly related to a constitutive active MAPK/ERK pathway. The AHR up-regulation followed by an increased expression of AHR target genes was confirmed by a meta-analysis of published microarray data, suggesting a ligand-independent active AHR pathway in PTC. In-vitro studies using a PTC-derived cell line (BCPAP) and HEK293 cells showed that BRAFV600E may directly modulate AHR localization, induce AHR expression and activity in an exogenous ligand-independent manner. The AHR pathway might represent a potential novel therapeutic target for PTC in the clinical practice.

Mitogen-Activated Protein Kinase Pathway: Genetic Analysis of 95 Adrenocortical Tumors

Mitogen-activated protein kinase (MAPK) pathway is often deregulated in adrenocortical tumors (ACT) but with no concrete data confirming alteration rate. The objective of this study was to evaluate genetic alterations in key components of MAPK pathway. We found one BRAF mutation (p.V600E) and four HRAS silent mutations. No alteration was found in NRAS, KRAS, EGFR genes. The patient carrying BRAF mutation was further characterized by investigating his biomolecular and clinico-pathological findings. Therefore, even if MAPK signaling is activated in ACT, our results suggest that genetic alterations do not seem to represent a frequent mechanism of ACT tumorigenesis.

Functional significance of the novel H-RAS gene mutation M72I in a patient with medullary thyroid cancer.

Medullary thyroid cancer (MTC) accounts for around 5-10% of all thyroid cancers. Though usually sporadic, 1 in 4 cases are of genetic origin, with germinal mutations in the RET proto-oncogene in familial forms and somatic mutations both in RET and in the RAS family genes in sporadic ones.This study aimed to characterize a rare H-RAS sequence variant -M72I- in a patient with sporadic MTC, focusing on its functional significance.Mutation analysis was performed for the RET, N-RAS, K-RAS and H-RAS genes by direct sequencing. Western blot analysis was done on 4 thyroid tissues from 1 patient carrying the M72I mutation in H-RAS, 1 with the Q61R mutation in H-RAS, 1 with no RET, H-RAS, K-RAS or N-RAS gene mutations, and 1 normal thyroid, using different antibodies against Erk1/2, phospho-Erk1/2 (Thr202/Tyr204), Akt and phospho-Akt (Ser473). Large-scale molecular dynamics simulations were completed for H-RAS wt and H-RAS M72I.Western blot analysis demonstrated that both MAPK and PI3K/Akt pathways were activated in the MTC patient carrying the M72I variant. In silico results showed conformational changes in H-RAS that could influence its activation by Sos and phosphate binding. Results of molecular dynamics were consistent with Western blot experiments.The M72I mutation may contribute effectively to proliferation and survival signaling throughout the MAPK and PI3K/Akt pathways. This work underscores the importance of studying genetic alterations that may lead to carcinogenesis.