A case of thrombopoietin-producing ovarian carcinoma confirmed by immunohistochemistry

The "Janus Face" of Platelets in Cancer

Besides their vital role in hemostasis and thrombosis, platelets are also recognized to be involved in cancer, where they play an unexpected central role: They actively influence cancer cell behavior, but, on the other hand, platelet physiology and phenotype are impacted by tumor cells. The existence of this platelet-cancer loop is supported by a large number of experimental and human studies reporting an association between alterations in platelet number and functions and cancer, often in a way dependent on patient, cancer type and treatment. Herein, we shall report on an update on platelet-cancer relationships, with a particular emphasis on how platelets might exert either a protective or a deleterious action in all steps of cancer progression. To this end, we will describe the impact of (i) platelet count, (ii) bioactive molecules secreted upon platelet activation, and (iii) microvesicle-derived miRNAs on cancer behavior. Potential explanations of conflicting results are also reported: Both intrinsic (heterogeneity in platelet-derived bioactive molecules with either inhibitory or stimulatory properties; features of cancer cell types, such as aggressiveness and/or tumour stage) and extrinsic (heterogeneous characteristics of cancer patients, study design and sample preparation) factors, together with other confounding elements, contribute to “the Janus face” of platelets in cancer. Given the difficulty to establish the univocal role of platelets in a tumor, a better understanding of their exact contribution is warranted, in order to identify an efficient therapeutic strategy for cancer management, as well as for better prevention, screening and risk assessment protocols.

Thrombopoietin Secretion by Human Ovarian Cancer Cells

The thrombopoietin (TPO) gene expression in human ovary and cancer cells from patients with ovarian carcinomatosis, as well as several cancer cell lines including MDA-MB231 (breast cancer), K562 and HL60 (Leukemic cells), OVCAR-3NIH and SKOV-3 (ovarian cancer), was performed using RT PCR, real-time PCR, and gene sequencing. Human liver tissues are used as controls. The presence of TPO in the cells and its regulation by activated protein C were explored by flow cytometry. TPO content of cell extract as well as plasma of a patient with ovarian cancer was evaluated by ELISA. The functionality of TPO was performed in coculture on the basis of the viability of a TPO-dependent cell line (Ba/F3), MTT assay, and Annexin-V labeling. As in liver, ovarian tissues and all cancer cells lines except the MDA-MB231 express the three TPO-1 (full length TPO), TPO-2 (12 bp deletion), and TPO-3 (116 pb deletion) variants. Primary ovarian cancer cells as well as cancer cell lines produce TPO. The thrombopoietin production by OVCAR-3 increased when cells are stimulated by aPC. OVCAR-3 cell's supernatant can replace exogenous TPO and inhibited TPO-dependent cell line (Ba/F3) apoptosis. The thrombopoietin produced by tumor may have a direct effect on thrombocytosis/thrombosis occurrence in patients with ovarian cancer.

Thrombopoietin: a novel candidate tumor marker for the diagnosis of ovarian cancer

Objective

To investigate the decisive role of preoperative serum thrombopoietin levels in the discrimination of benign and malignant ovarian pathologies and its value in the evaluation of treatment response.

Methods

Fifty patients with diagnoses of adnexal masses (25 benign, 25 malignant) were included in the study. Blood samples were collected from all cases preoperatively. Age, menopausal status, adnexal mass size, preoperative CA-125 level, platelet count, the stage of the disease (FIGO stage), tumor grade, histologic subgroup, the residual tumor mass, ascites cytology, surgical procedures, and postoperative treatments were recorded for the malignant group. Response to treatment was evaluated based on the revised RECIST guideline.

Results

The preoperative serum thrombopoietin levels of the malignant cases (median, 98; range, 7 to 768) were significantly higher when compared with those of benign cases (median, 27; range, 13 to 131; p=0.004). The positive predictive value of CA-125 was found to be 79%, when it was used as a single marker; however it had risen to 85% when both CA-125 and thrombopoietin levels were used. There was no significant relationship between preoperative serum thrombopoietin levels and tumor grade, ascites cytology, presence of residual mass, and response to treatment. The preoperative serum thrombopoietin levels were significantly higher in stage III-IV cases and cases with serous histology. The post-treatment serum thrombopoietin levels in the malignant group were significantly lower as compared with the preoperative thrombopoietin levels.

Conclusion

Thrombopoietin can play an additive role for prediction of ovarian cancer.

Tumor-platelet interaction in solid tumors

Elevated platelet counts in patients diagnosed with malignant tumors were first described more than 100 years ago. Today it is well known that in many types of solid tumors, thrombocytosis at the time of diagnosis is associated with shorter survival. From this well-documented clinical correlation between platelet count and prognosis of solid tumors, the following questions arise: (i) Are the increased platelet counts the reason for shortened survival as platelet-secreted cytokines might boost tumor growth and angiogenesis? (ii) Do platelets affect tumor metastasis thereby shortening survival time? or (iii) Are increased platelet counts simply an epiphenomenon of tumor growth with larger tumors resulting in higher platelet counts and shorter survival times? We address these three questions within our review of the current literature to provide a comprehensive overview of the current concepts in tumor-platelet interaction.

Thrombopoietin and its splicing variants: structure and functions in thrombopoiesis and beyond

Since its cloning in 1994, several studies have reported that thrombopoietin (THPO) presents several alternative splicing products that differ from the full-length protein in its 5' UTR, N- or C-terminal regions. Most of these splice variants are evolutionarily conserved and have been detected in different tissues as well as in cell lines. Although the possible functions of the THPO isoforms are still elusive, different clues link them to the peculiar mechanism that regulates THPO production. Moreover, novel fields to explore possible roles of the THPO variants are opened by observations that this hormone can influence the formation of hematopoietic progenitors and its expression occurs in some tumors as well as in tissues not directly related to the thrombopoiesis. In this review, we summarize the structure and functions of THPO through the published evidence on its splicing isoforms and discuss about their involvement with physiopathologic phenomena.

Preoperative serum thrombopoietin levels are higher in patients with ovarian cancer than with benign cysts

OBJECTIVE

To assess the diagnostic relevance of serum thrombopoietin (TPO) levels, we compared serum TPO levels between the patients with ovarian cancer and benign ovarian cysts. We also correlated serum TPO concentrations in ovarian cancer patients to know prognostic factors such as disease stage, tumor grade, histological subtype, and residual tumor mass.

STUDY DESIGN

Preoperative serum TPO levels were measured in women with epithelial ovarian cancer (n=51) and women with benign ovarian cysts (n=25) using an enzyme-linked immunosorbent assay.

RESULTS

The serum TPO concentration was significantly elevated in the ovarian cancer patients as compared to the benign patient controls. Platelet counts and TPO in the serum did not correlate in the ovarian cancer patients. However, using a TPO cutoff of 90 pg/ml and a CA125 cutoff of 30 units/ml, when both markers were elevated, the specificity was as high as 92%.

CONCLUSION

Serum TPO concentrations may have a role in the diagnostic clinical setting for discerning benign from malignant ovarian tumors.