No Impact of PolySia-NCAM Expression on Treatment Response in Neuroendocrine Neoplasms of the Lung.

BACKGROUND: Polysialic acids (abbr. polySia) are found on numerous tumors, including neuroendocrine lung tumors. They have previously been shown to impact metastatic potential, as they can influence the signaling and adhesion properties of neuronal cell adhesion molecules (abbr. NCAM) and other cell adhesion molecules. Therefore, the aim of this small pilot study was to analyze whether there was a correlation between polySia-NCAM expression and specific clinical or histopathologic characteristics, and if polySia-NCAM expression had an impact on treatment response, disease progression and prognosis of lung neuroendocrine neoplasms. METHODS: This work was based on an analysis of 28 digitized patient records and corresponding patient samples. The response to therapy was radiologically determined at the time of diagnosis and at certain intervals during therapy following the current RECIST1.1 and volumetric sphere calculation. To analyze whether polySia-NCAM expression had prognostic relevance, polySia-NCAM-positive and -negative cases were compared in a Kaplan-Meier survival analysis. FINDINGS: A majority of 78.6% lung neuroendocrine neoplasms showed a strong staining signal for polySia-NCAM. There was a significant correlation between expression and histopathological grade (p = 0.0140), since carcinoids were less likely polySia-NCAM-positive compared to small cell lung carcinoma (abbr. SCLC) and large cell neuroendocrine carcinomas of the lung (abbr. LCNEC). There was no significant association between polySia-NCAM expression and clinical characteristics (age: p = 0.3405; gender: p = 0.6730; smoking history: p = 0.1145; ECOG: p = 0.1756, UICC8 stage: p = 0.1182) or radiologically determined disease progression, regardless of the criteria used to categorize response (RECIST 1.1: p = 0.0759; sphere: p = 0.0580). Furthermore, polySia-NCAM expression did not affect progression-free survival (p = 0.4198) or overall survival (p = 0.6918). INTERPRETATION: PolySia-NCAM expression was more common in high-grade compared to low-grade neuroendocrine neoplasms of the lung; however, this small pilot study failed to show an association between polySia-NCAM expression and response to therapy.

Parathyroid hormone-related protein confers chemoresistance by blocking apoptosis signaling via death receptors and mitochondria.

Parathyroid hormone (PTH) has a central role in the regulation of serum calcium and phosphate, whereas parathyroid hormone-related peptide (PTHrP) has important developmental roles. In addition, PTHrP has been discovered as a causative agent of hypercalcemia of malignancy. PTHrP is also expressed in many tumors, and expression often correlates with unfavorable prognosis. We have investigated the effects of PTHrP on apoptosis signaling pathways initiated by DNA damaging chemotherapeutic drugs. Stimulation experiments of the CD95-, the TNF-R-, and the TRAIL-R-death receptor systems in Saos human osteosarcoma cells revealed that PTHrP can block signaling via each of these death receptors. Furthermore, our findings demonstrate a link between PTHrP and the mitochondrial apoptosis pathway. PTHrP down-regulates expression of pro-apoptotic Bcl-2 family members like Bax and PUMA and up-regulates expression of antiapoptotic molecules like Bcl-2 and Bcl-xl. It is of clinical relevance that PTHrP and anticancer drugs show opposing interactions on death receptor-triggered as well as on mitochondrial apoptosis pathways. In addition, PTHrP induces chemoresistance by interference with p53 family-dependent apoptosis signaling pathways and p53-mediated transactivation of apoptosis target genes. Inhibition of CD95- and Bax gene transactivation is a mechanism by which PTHrP reduced the apoptosis response and treatment sensitivity of tumor cells. Our data indicate that PTHrP inhibits major apoptosis signaling pathways by blocking signaling via p53, death receptors and mitochondria and, consequently, confers chemoresistance of cancer cells. Thus, beyond its importance in development and differentiation, we describe an important role for PTHrP in tumorigenesis.

Activation of the receptor for parathyroid hormone and parathyroid hormone related protein induces apoptosis via the extrinsic and intrinsic signaling pathway.

Parathyroid hormone (PTH) is the primary regulator of serum calcium homeostasis and bone metabolism. PTH acts primarily by binding to its receptor, PTH1R, in the bone and kidney. In addition to PTH, PTH1R also recognizes PTH-related peptide (PTHrP), a paracrine/autocrine factor originally described as the hormone responsible for hypercalcemia of malignancy. PTHrP is developmentally regulated and expressed, and it has been shown to play a physiological role in development, differentiation, cell proliferation and survival. We investigated the effects of PTH1R activation on the apoptosis signaling programs of human embryonic kidney (HEK) cells. Stimulation experiments of the CD95, TNF-R and TRAIL-R death receptor systems revealed that activation of PTH1R in HEK cells triggers signaling via each of these death receptors. Furthermore, our findings demonstrate a link between activation of PTH1R and the mitochondrial apoptosis pathway. PTHR1R overexpression led to an alteration of the mitochondrial membrane potential and activation of the intrinsic apoptosis signaling pathway. Our data indicate that activation of PTH1R engages major apoptosis signaling pathways by inducing signaling via death receptors and mitochondria in HEK cells. Thus, beyond its importance in development and differentiation, we describe an important role for the PTH/PTHrP receptor system in apoptosis of differentiating/embryonic cells.