Specific response of mouse tumor-feeding arterioles to stimulation by 5-HT1 agonists

Different serotonergic expression in nevomelanocytic tumors

The neuromediator serotonin (5-hydroxytryptamine; 5-HT) has been proposed to play a role in tumor progression. Thus, the aim of the present investigation was to determine whether alterations in the serotonergic system occur in nevomelanocytic tumors. For this purpose, paraffin-embedded biopsies of superficial spreading malignant melanoma (SSM), dysplastic compound nevi (DN) and benign compound nevi (BCN) were characterized with regard to their expression of 5-HT, the 5-HT1A and 5-HT2A receptors, and the serotonin transporter protein (SERT), by immunohistochemical analysis. Melanocytes in the region surrounding the tumor were found to express both the 5-HT1A and 5-HT2A receptors. Tumor cells that immunostained positively for the different serotonergic markers were observed in the suprabasal epidermis of DN tissue and, to an even greater extent, in the case of SSM. Furthermore, some of these latter cells expressed both 5-HT1AR and 5-HT2AR. The level of expression of 5-HT1AR at the junctional area was lower for SSM than for DN or BCN. As the degree of atypia increased, the intensity of tumor cell staining in the dermis for 5-HT1AR and SERT declined. Vessel immunoreactivity for 5-HT2A was more intense in SSM than in BCN tissue. Round-to-dendritic cells that expressed both SERT and 5-HT1AR were seen to infiltrate into the dermal region of the tumor, this infiltration being more evident in the case of DN and SSM. These latter cells were also tryptase-positive, indicating that they are mast cells. Thus, alterations in serotonergic system may be involved in nevomelanocytic tumors and mast cells may play an important role in this connection.

Effects of nefazodone on the development of experimentally induced tumors in stressed rodents

RATIONALE

Anxiety and depression are commonly encountered in patients with cancer and constitute risk and prognostic factors for the disease. Although previous findings do not support an overall association between the use of antidepressants and higher prevalence of cancer, results for serotonin uptake inhibitors are not entirely reassuring.

OBJECTIVES

We evaluated the effects of nefazodone, a serotonin and norepinephrine (NE) reuptake inhibitor and 5-HT(2A) receptor antagonist antidepressant, on the appearance of breast cancer induced by mammary tumor virus (MTV) in mice, and on the development of lung metastases in rats injected intravenously with Walker 256 (W-256) carcinosarcoma cells.

METHODS

Female C3H/He mice carrying the MTV were monitored for mammary tumor incidence and latent periods while being treated with a daily intraperitoneal injection with placebo or nefazodone. Rats were administered 10(4) W-256 cells, exposed to a chronic auditory stressor for 8 days, and then killed to evaluate metastatic nodules in the lungs.

RESULTS

Although all of the mice were potential candidates for MTV-induced breast cancer, those treated with nefazodone were partially protected against adverse effects of stress induced by the daily administration of placebo on both parameters. Relative to placebo, nefazodone reduced the stress-induced increase in the number and percentage area of metastases in the frontal section through pulmonary hilus and increased the survival periods of rats given W-256 cells and exposed to a chronic auditory stressor.

CONCLUSIONS

Our results provide evidence of the beneficial effects of nefazodone against the adverse effects of stress on tumor development and metastaticity in rodents, but did not show significant effects in unstressed rodents.

Expression of serotonin receptors and role of serotonin in human prostate cancer tissue and cell lines

BACKGROUND

Increase in the number of serotonin (5-HT) releasing neuroendocrine (NE) cells has been shown to be correlated with tumor progression, loss of androgen dependence, and poor prognosis. Serotonin is a well-known mitogen which mediates a wide variety of physiological effects via multiple receptors, of which receptor subtype 1 (5-HTR1) has been identified in prostate cancer (PC) cell lines. Recently, 5-HT has been found to show growth-promoting activity and to be functionally related to oncogenes.

MATERIALS AND METHODS

Localization, protein content, and mRNA expression of 5-HTR subtype 1A, 1B, and 1D was studied in prostatic tissue (35 patients), metastases, PC cell lines, a benign prostatic stromal cell line (human prostate cell preparation (hPCP)), and xenografts of PC-3 cells by immunohistochemistry (IHC), Western blotting, and RT-PCR, respectively. The growth-inhibition effect of a 5-HT1A antagonist (NAN-190) on PC cell lines was studied using a bromodeoxyuridine (BrdU) assay.

RESULTS

A strong immunoreaction of 5-HTR1A and 1B was demonstrated in high-grade tumor cells (35/35) and a small number of BPH cells, whereas 5-HTR1D was confined to vascular endothelial cells. 5-HTR1A was also demonstrated in PC cells metastasized to lymph node and bone, PC-3, DU145, LNCaP, and in xenografts of PC-3 cells and hPCP. Western blot analysis gave strong bands from PC tissue extracts compared to BPH tissue. Using RT-PCR, 5-HTR1A mRNA was demonstrated in all PC cell lines. An antagonist of 5-HTR1A (NAN-190) inhibited the growth of PC-3, DU145, and LNCaP cells but not of hPCP cells.

CONCLUSIONS

This is the first study demonstrating an overexpression of 5-HTR subtypes 1A and 1B in PC cells, especially in high-grade tumors. Moreover, 5-HT stimulates proliferation of PC cells and 5-HTR1A antagonists inhibit proliferation. Thus, we propose that 5-HT has an important role in tumor progression, especially in the androgen-independent state of the disease. The design of specific antagonists for this type of receptor might be useful for the growth control of androgen-independent tumors.

Impact of serotonin on tumour growth

Several opposite effects of serotonin (5HT) on tumour growth have been reported. On one hand, 5HT is known as a growth factor for several types of nontumoural cells, and it has been proposed to take part in the autocrine loops of growth factors contributing to cell proliferation in aggressive tumours such as small cell lung carcinoma. Depending on the tumour type either 5HT2 or 5HT1 receptor antagonist have been found to inhibit the 5HT-induced increase in tumour growth. In contrast, several authors have also reported that 5HT and 5HT2 agonist can inhibit tumour growth. Most often this effect has been considered to be related with the specific vasoconstrictive effect of 5HT or 5HT2 agonists on the vessels irrigating the tumour, which has been evidenced by intravital microscopy. Intravital microscopy studies have also shown that vessels perfusing the tumour exhibit a specific vasconstrictive response to 5HT1 agonists. In addition, 5HT has been shown to be involved in the effects of several anticancer treatments associated with the reduction of tumour flow. Finally, the specific vasoconstrictive effect of 5HT or 5HT receptor subtype agonists might also be useful in inducing hypoxia in tumours, which could be exploited in a strategy using hypoxia-selective cytotoxins or hypoxia-selective gene therapy.

Reduction of tumour blood flow with KB-R8498 potentiates the response of tumours to hyperthermia

The anti-tumour activity and the effect on tumour and normal tissue perfusion of a newly discovered anticancer agent, KB-R8498 (Kanebo Ltd., Osaka, Japan), were investigated in FSa II tumours of C3H mice. The tumour perfusion, as measured by the 86Rb-uptake method, markedly decreased with relatively little change in the normal tissue perfusion after an i.v. injection of KB-R8498. Furthermore, the drug potentiated the effect of hyperthermia at 42.5 degrees C for 60 min to suppress the tumour growth. The results suggest that the preferential reduction in tumour blood flow relative to normal tissue blood flow by KB-R8498 may be exploited to enhance the anti-tumour effect of hyperthermia.