A phase I study of the somatostatin analogue somatuline in patients with metastatic hormone-refractory prostate cancer

Is There a Standard Chemotherapeutic Regimen for Hormone-Refractory Prostate Cancer? Present and Future Approaches in the Management of the Disease

Prostate cancer that no longer responds to hormonal manipulation can be defined as hormone-refractory prostate cancer. Until recently, there has been no standard chemotherapeutic approach for hormone-refractory prostate cancer. The major benefits of chemotherapy in the treatment of the disease are palliative in nature, in terms of reduction of pain and use of analgesics and improvement of performance status, as followed in the most recent trials. Phase III studies are necessary to better evaluate the efficacy of the different regimens, because several old studies suffer for methodological deficits. There is a promising activity of new drug combinations, such as vinca alkaloids and taxanes. Phase I and II trial are testing combinations of classic chemotherapeutic agents and biologic drugs, and the first results appear interesting. In this article, recent advances in the treatment of hormone-refractory prostate cancer using chemotherapeutic regimens are critically reviewed.

Clinical studies in humans targeting the various components of the IGF system show lack of efficacy in the treatment of cancer

The insulin-like growth factors (IGFs) system regulates cell growth, differentiation and energy metabolism and plays crucial role in the regulation of key aspects of tumor biology, such as cancer cell growth, survival, transformation and invasion. The current focus for cancer therapeutic approaches have shifted from the conventional treatments towards the targeted therapies and the IGF system has gained a great interest as anti-cancer therapy. The proliferative, anti-apoptotic and transformation effects of IGFs are mainly triggered by the ligation of the type I IGF receptor (IGF-IR). Thus, aiming at developing novel and effective cancer therapies, different strategies have been employed to target IGF system in human malignancies, including but not limited to ligand or receptor neutralizing antibodies and IGF-IR signaling inhibitors. In this review, we have focused on the clinical studies that have been conducted targeting the various components of the IGF system for the treatment of different types of cancer, providing a description and the challenges of each targeting strategy and the degree of success.

Characterization and sub-cellular localization of SS1R, SS2R, and SS5R in human late-stage prostate cancer cells: effect of mono- and bi-specific somatostatin analogs on cell growth

Somatostatin (SST) and SST receptors (SS1R, SS2R, SS3R, SS4R and SS5R) appear to play a significant role in the progression of human prostate cancer (PCa), which is associated with heterogeneity of SSRs expression and specific cell localization as we already demonstrated in the LNCaP cell line, an in vitro model of human androgen-dependent PCa. In this study, PC-3 and DU-145 human castration-resistant PCa cells were found to express all SSRs, while LNCaP expressed all but SS4R. A 48-h treatment with BIM-23244 (SS2R/SS5R) or BIM-23926 (SS1R) SST analogs was more effective in inhibiting cell proliferation, compared to BIM-23120 (SS2R), BIM-23206 (SS5R) and BIM-23704 (SS1R/SS2R). BIM-23926 (SS1R) treatment increased the amount of p21 and decreased phosphorylated (p) ERK1/2. BIM-23244 (SS2R/SS5R) led to p21 increment only in PC-3 cells, and to pERK1/2 reduction in both cell lines. SS1R/SS2R and SS2R/SS5R receptor dimers were natively present on cell membrane and their amount was increased by BIM-23704 (SS1R/SS2R) or BIM-23244 (SS2R/SS5R) treatment, respectively. SS1R, SS2R and SS5R were differently distributed among nuclear, lysosomal and microsomal compartment, according to their different recycling dynamics. These results show that, in PC-3, DU-145 and LNCaP cells, activation of SS1R and SS2R/SS5R leads to relevant antiproliferative effects.

Prognostic role of neuroendocrine differentiation in prostate cancer, putting together the pieces of the puzzle

Neuroendocrine (NE) differentiation is a common feature in prostate cancer (PC). The clinical significance of this phenomenon is controversial; however preclinical and clinical data are in favor of an association with poor prognosis and early onset of a castrate resistant status. NE PC cells do not proliferate, but they can stimulate the proliferation of the exocrine component through the production of paracrine growth factors. The same paracrine signals may favor the outgrowth of castrate adapted tumors through androgen receptor dependent or independent mechanisms. Noteworthy, NE differentiation in PC is not a stable phenotype, being stimulated by several agents including androgen deprivation therapy, radiation therapy, and chemotherapy. The proportion of NE positive PC, therefore, is destined to increase during the natural history of the disease. This may complicate the assessment of the prognostic significance of this phenomenon. The majority of clinical studies have shown a significant correlation between NE differentiation and disease prognosis, confirming the preclinical rationale. In conclusion the NE phenotype is a prognostic parameter in PC. Whether this phenomenon is a pure prognostic factor or whether it can influence the prognosis by favoring the onset of a castrate resistance status is a matter of future research.

Regulation of prostate cancer cell proliferation by somatostatin receptor activation

Although some evidence supports the antitumoral effects of somatostatin (SRIF) and related agonists, the available data in prostate cancer (PCa) model systems and clinical studies are few, conflicting and not conclusive. This study investigated the effects of lanreotide and new mono- and bi-specific SRIF agonists on proliferation, ligand-driven SRIF receptor (sst) dimerization and secretory pattern of the IGF system in LNCaP cells, a model of androgen-dependent PCa. LNCaP expressed all sst(s), but sst(4). Among them, sst(1) and sst(3) were inversely regulated by serum concentration. sst(1)/sst(2) and sst(2)/sst(5) dimers were constitutively present and further stabilized by treatment with BIM-23704 (sst(1)/sst(2)) and BIM-23244 (sst(2)/sst(5)), respectively. Dose-response studies showed that lanreotide and BIM-23244 were significantly more potent in inhibiting LNCaP cell proliferation than BIM-23120 (sst(2)) and BIM-23206 (sst(5)) alone or in combination. Treatment with BIM-23926 [corrected] (sst(1)) markedly reduced cell proliferation, whereas exposure to BIM-23704 resulted in a lower cell growth inhibition. The antiproliferative effects of BIM-23244, lanreotide and BIM-23704 were unchanged, reduced and abolished by the sst(2) antagonist BIM-23627, respectively. All SRIF analogs caused a significant induction in p27(KipI) and p21 and down-regulation of protein expression of cyclin E, as well as reduced IGF-I and IGF-II secretion. In particular, the administration of exogenous IGF-I, at variance to IGF-II, counteracted the inhibitory effect on cell proliferation of these compounds. Moreover, SRIF agonists reduced endogenous IGFBP-3 proteolysis. These results show that, in LNCaP cells, activation of sst(1) and sst(2)/sst(5) results in relevant antiproliferative/antisecretive actions.

Somatostatin analog lanreotide in the treatment of castration-resistant prostate cancer (CRPC)

Prostate cancer is a common disease affecting males. Despite initial sensitivity to hormone treatment, prostate cancer eventually progresses to a castration-resistant stage (CRPC), which carries an ominous prognosis. Lanreotide is a long-acting somatostatin analog with the same properties with the native peptide. It has been shown to be highly efficacious in treating various hypersecretoty disorders and tumors. Lanreotide has been administered to patients with CRPC within a novel treatment concept, with the aim of targeting not only cancer cells but also various factors secreted in the tumor cell milieu that confer protection from apoptosis. Within this concept, lanreotide has been administered as part of the "antisurvival factor therapy" in combination with dexamethasone and a gonadotropin releasing hormone (GnRH) analog. It has also been given combined with oestrogens in patients with CRPC. The so far published series have documented a clinical response in many patients treated along with significant improvement in parameters related to quality of life. In view of these promising results, large-scale, randomized, controlled trials are warranted to clearly define the exact role of lanreotide and other somatostatin analogs in the treatment of patients with CRPC.

Neuroendocrine differentiation in the progression of prostate cancer

Neuroendocrine (NE) cells originally exist in the normal prostate acini and duct, regulating prostatic growth, differentiation and secretion. Clusters of malignant NE cells are found in most prostate cancer (PCa) cases. NE differentiation (NED) is the basic character of the prostate, either benign or malignant. NE cells hold certain peptide hormones or pro-hormones, which affect the target cells by endocrine, paracrine, autocrine and neuroendocrine transmission in an androgen-independent fashion due to the lack of androgen receptor. NED is accessed by immunohistochemical staining or measurement of serum levels of NE markers. The extent of NED is associated with progression and prognosis of PCa. Chromogranin A (CGA) is the most important NE marker. In metastatic PCa, pretreatment serum CGA levels can be a predictor for progression and survival after endocrine therapy. It is recommended to measure longitudinal change in serum CGA. The NE pathway can also be a therapeutic target.

Future clinical prospects in somatostatin/cortistatin/somatostatin receptor field

Somatostatin receptors (sst), somatostatin (SS) and cortistatin (CST) are widely expressed in the various systems in the human and rodent organisms and are "responsible" for maintaining homeostasis, which is essential for survival. Because of their broad expression pattern sst, SS and CST interactions may play regulatory roles in both physiology and pathophysiology in mammalian organisms. SS analogue treatment strategies as well as the use of SS analogues for diagnostic purposes have been established in diseases of different origins. This review focuses on the currently determined role for SS analogues in today's clinical practice and the potential clinical prospects for SS, CST and sst interactions in the future, with a focus on neuroendocrine and non-neuroendocrine tumours and immune-mediated diseases. Moreover, the role of new SS analogues and new insights in sst physiology will be discussed.

Evaluation of IGF-I levels during long-term somatostatin analogs treatment in patients with gastroenteropancreatic endocrine tumors

Previous experiments reported desensitization to SS action in rat anterior pituitary cells and cell lines. The aim of the study was to verify whether the lack of desensitization to SS analogs (SSa) observed in acromegalic patients was also present in subjects with normal hypothalamic-pituitary function. The effect of chronic treatment with octreotide long-acting release (o-LAR, 10-30 mg/28 days) on IGF-I levels was then evaluated in 23 patients with gastroenteropancreatic (GEP) endocrine tumors (8 gastrinomas, 6 carcinoids, and 9 functioning pancreatic tumors). Serum IGF-I, clinical symptoms, plasma chromogranin-A (CgA) and markers of hepatic synthesis were evaluated before and after a short-term period in all the patients (median 4.5 months), after a medium-term period in 12 (median 18 months) and after a long-term follow-up period in 9 of them (median 48 months). Mean IGF-I levels decreased from 17.3+/-7.0 to 12.8+/-6.2 nmol/l in the short-term (p<0.005) being reduced from baseline concentrations in 87% and under the normal range for age in 35% of patients. Afterwards, they always remained stable both in the medium- and long-term periods, still being low in 3/12 and 2/9 patients, respectively. No alterations in biochemical markers of liver function were found either before or during therapy. No correlation between IGF-I levels, CgA concentrations and/or clinical definitive outcome was observed. In conclusion, the study demonstrated that: a) similarly to that observed in acromegalic patients, chronic o-LAR treatment did not induce desensitization of pituitary SS receptors (SSR) in humans with intact hypothalamic-pituitary axis, and b) in patients with GEP endocrine tumors, GH/IGF-I inhibition did not contribute to SSa efficacy.

Combination therapy using LHRH and somatostatin analogues plus dexamethasone in androgen ablation refractory prostate cancer patients with bone involvement: a bench to bedside approach

The development of resistance to anticancer therapies is a major hurdle in preventing long-lasting clinical responses to conventional therapies in hormone-refractory prostate cancer. Herein, the molecular evidence documenting that bone metastasis microenvironment survival factors (mainly the paracrine growth hormone-independent, urokinase-type plasminogen activator-mediated increase of IGF-1 and the endocrine production of growth hormone-dependent IGF-1, mainly liver-derived IGF-1 production) produce an epigenetic form of prostate cancer cells that are resistant to proapoptotic therapies is reviewed. Consequently, the authors present the conceptual framework of a novel antibone microenvironment survival factor, mainly an anti-IGF-1 hormonal manipulation for androgen ablation refractory prostate cancer (a combination of conventional androgen ablation therapy [luteinising hormone-releasing hormone agonist-A or orchiectomy]) with dexamethasone plus somatostatin analogue, which yielded durable objective responses and major improvement of bone pain and performance status in stage D3 prostate cancer patients.

Octreotide scintigraphy and Chromogranin A do not predict clinical response in patients with octreotide acetate-treated hormone-refractory prostate cancer

In this pilot study, the predictive value of Octreotide scintigraphy (Octreoscan) and/or Chromogranin-A (CgA) was investigated in patients with hormone-refractory prostate cancer treated with Octreotide acetate. In total, 20 patients with progressive disease and bone metastases entered the trial. At baseline Octreoscan, CgA, PSA, alkaline phosphates (ALP) and two self-administered questionnaires (EORTC QLQ C-30 (v3) and brief pain index) were performed and a diary of the pharmaceutical was started. The treatment consisted of Octreotide (Sandostatin LAR) acetate 30 mg intramuscular injection every month. The blood samples and questionnaires were repeated every month until 3 months. Clinical responder was defined as a patient with increased global health score more than 10 units and stable or decreased pain score without an increase in analgesic. In all, 17 patients were treated per protocol, and four were assessed as clinical responders. Six patients developed a reduction in ALP (median -26%, range -5 to -78%). All patients increased in PSA. At baseline, three patients had a negative Octreoscan and the patients with positive lesions, demonstrated uptake of low intensity. At baseline the CgA was elevated above the normal range in 15 of the patients, and during treatment five patients decreased their CgA to the normal range. Neither baseline Octreoscan nor CgA could identify the clinical reponders. A minority of patients improves their health-related quality of life. The decrease and normalization of CgA levels in five patients during therapy indicates therapeutic activity but Octreoscan and CgA could not identify clinical responders.

SOMATOSTATIN ANALOGUES AND ESTROGENS IN THE TREATMENT OF ANDROGEN ABLATION REFRACTORY PROSTATE ADENOCARCINOMA

PURPOSE

Prostate cancer progression to androgen ablation refractory stage D3 corresponds to cancer cell escape from androgen withdrawal induced apoptosis. Of note, salvage chemotherapy can extend the median survival of approximately 10 months in patients with stage D3. Therefore, novel therapeutic strategies that target the molecular basis of androgen resistance are required.

MATERIALS AND METHODS

The MEDLINE and Current Content databases were used to find studies of the use of estrogens and somatostatin analogues for D3 prostate adenocarcinoma. We also analyzed the rationale and clinical results of our combination therapy using lanreotide and ethinylestradiol.

RESULTS

Negative experiences have been reported with somatostatin analogues as monotherapy. On the other hand, the median progression-free survival reported in our experience using lanreotide acetate plus ethinylestradiol clearly surpassed the 10-month survival historically described in stage D3 cases.

CONCLUSIONS

The use of somatostatin analogues in combination therapy for D3 prostate cancer sustains the novel concept in cancer treatment in which therapies may target not only cancer cells, but also the microenvironment in combination, which can confer protection from apoptosis.

[Phosphotyrosine phosphatase SHP-1, somatostatin and prostate cancer]

We review the mechanisms involved in prostatic growth based on androgens and product of neuroendocrine secretion, with special reference to the role of somatostatin (SS) in the inhibition of neoplastic growth. Our contributions in the field confirm the antiproliferative effect of SS on the prostate is mediated by phosphotyrosine phosphatase SHP-1, that is present in human prostate. This enzyme plays a role in the control of prostatic cell proliferation and in the progression of prostate cancer. Besides, we consider its presence may determine the therapeutic potential of SS in the control of prostate cancer.

Combination of Somatostatin Analog, Dexamethasone, and Standard Androgen Ablation Therapy in Stage D3 Prostate Cancer Patients with Bone Metastases

PURPOSE

Androgen ablation-refractory prostate cancer patients (stage D3) develop painful bone metastases and limited responsiveness to conventional therapies, hence the lack of universally accepted "gold standard" treatment for this poor prognosis clinical setting. We tested the safety and efficacy in stage D3 patients of the combination hormonal therapy, which combines administration of somatostatin analog and dexamethasone with standard androgen ablation monotherapy (luteinizing-hormone releasing-hormone analog or orchiectomy).

EXPERIMENTAL DESIGN

Thirty eight patients with stage D3 prostate cancer (mean age 71.8 +/- 5.9 years) continued receiving androgen ablation therapy in combination with oral dexamethasone (4 mg daily for the 1st month of treatment, tapered down to 1 mg daily by the 4th month, with 1 mg daily maintenance dose thereafter) and somatostatin analog (20 mg octreotide i.m. injections every 28 days).

RESULTS

Twenty-three of 38 patients (60.5%) receiving this combination regimen had partial responses [PR, >/=50% prostate-specific antigen (PSA) decline], 9 (21.1%) had stable disease, and 7 (18.4%) had progressive disease. In 47.7% (18 of 38) of patients, their serum PSA levels decreased with treatment but did not return to their respective baselines until the end of follow-up (or death from non-prostate cancer-related causes). The median time-to-return to baseline PSA was 12 months (95% CI, 7-17 months), median progression-free survival was 7 months (95% CI, 4.5-9.5 months), median overall survival was 14 months (95% CI, 10.7-17.4 months), and median prostate cancer-specific overall survival (defined as time from onset of combination therapy until prostate cancer-related death) was 16.0 months (95% CI, 11.9-20.1 months). All patients reported significant and durable improvement of bone pain and performance status (for a median duration of 14 months; 95% CI, 9-19 months), without major treatment-related side effects. We observed a statistically significant (P < 0.01) reduction in serum insulin-like growth factor-1 levels at response to the combination therapy. T levels remained suppressed within castration levels at baseline and throughout therapy, including relapse.

CONCLUSION

The combination therapy of dexamethasone plus somatostatin analog and standard androgen ablation manipulation produces objective clinical responses and symptomatic improvement in androgen ablation-refractory refractory prostate cancer patients.

Somatostatin receptors: from basic science to clinical approach. Unlabeled somatostatin analogues-1: Prostate cancer

Neuroendocrine cells have been found in all the stages of prostate cancer, but their clinical significance is not completely understood. Neuroendocrine cells are androgen receptor- and prostate-specific antigen-negative, do not proliferate, and secrete many neuropeptides, such as chromogranin A. Neuroendocrine differentiation of prostate cancer correlates with an advancing tumour stage, poor prognosis and tumour progression after androgen deprivation. Furthermore, neuroendocrine phenotype is associated with the increased expression of neo-angiogenesis and vascular endothelial growth factor and with an over-expression of survivin, a new anti-apoptosis protein. Chromogranin A is the quantitatively major secretory protein of the vesicles inside neuroendocrine prostate cells and it is the marker most frequently used to detect neuroendocrine features, both in tissues and in general circulation. Tumours displaying neuroendocrine phenotype tend to be more aggressive and resistant to hormone-therapy. Neuroendocrine differentiation seems to be a dynamic phenomenon: in vitro and in vivo data suggest that it can be induced by androgen suppression. Moreover, the differences in the expression of somatostatin receptors between primary and hormone-refractory prostate cancer are likely to be related to the changes in neuroendocrine phenotype during androgen deprivation. Circulating chromogranin A levels seem to be scarcely affected by endocrine- and chemotherapy, while they significantly decreased after treatment with somatostatin analogs.

Peptide receptors as molecular targets for cancer diagnosis and therapy

During the past decade, proof of the principle that peptide receptors can be used successfully for in vivo targeting of human cancers has been provided. The molecular basis for targeting rests on the in vitro observation that peptide receptors can be expressed in large quantities in certain tumors. The clinical impact is at the diagnostic level: in vivo receptor scintigraphy uses radiolabeled peptides for the localization of tumors and their metastases. It is also at the therapeutic level: peptide receptor radiotherapy of tumors emerges as a serious treatment option. Peptides linked to cytotoxic agents are also considered for therapeutic applications. The use of nonradiolabeled, noncytotoxic peptide analogs for long-term antiproliferative treatment of tumors appears promising for only a few tumor types, whereas the symptomatic treatment of neuroendocrine tumors by somatostatin analogs is clearly successful. The present review summarizes and critically evaluates the in vitro data on peptide and peptide receptor expression in human cancers. These data are considered to be the molecular basis for peptide receptor targeting of tumors. The paradigmatic peptide somatostatin and its receptors are extensively reviewed in the light of in vivo targeting of neuroendocrine tumors. The role of the more recently described targeting peptides vasoactive intestinal peptide, gastrin-releasing peptide, and cholecystokinin/gastrin is discussed. Other emerging and promising peptides and their respective receptors, including neurotensin, substance P, and neuropeptide Y, are introduced. This information relates to established and potential clinical applications in oncology.

Somatostatin analogs and radiopeptides in cancer therapy

Since the discovery of somatostatin (sst) in 1973, numerous chemical and biological studies have been carried out to develop sst analogs with enhanced resistance to proteases and prolonged activity. Three highly potent sst analogs-octreotide, lanreotide, and vapreotide-are now available in the clinic, and demonstrate efficacy in the treatment of tumors of the pituitary and the gastroenteropancreatic tract. The most striking effect is the control of hormone hypersecretion associated with these tumors. Available data on growth suppression in patients indicate a limited antiproliferative action, tumor shrinkage is observed in 10-20% patients, and tumor stabilization in about half of the patients for duration of 8-16 months. Eventually, however, all patients escape from sst analog therapy with regard to both hormone hypersecretion and tumor growth, the only exception being observed in acromegalic patients who do not experience tachyphylaxis even after more than 10 years of daily octreotide injection. The mechanism underlying the escape phenomenon is not yet clarified. Regarding the molecular mechanisms involved in sst antineoplastic activity, both indirect and direct effects via specific somatostatin receptors (SSTRs) expressed in the target cells have be described. Direct action may result from blockade of mitogenic growth signal or induction of apoptosis following interaction with SSTRs. Indirect effects may be the result of reduced or inhibited secretion of growth-promoting hormones and growth factors that stimulate the growth of various types of cancer; also, inhibition of angiogenesis or influence on the immune system are important factors. Five SSTR subtypes have been identified so far, which are variably expressed in a variety of tumors such as gastroenteropancreatic (GEP) tumors, pituitary tumors, and carcinoid tumors. Although all five SSTR subtypes are linked to adenylate cyclase, they are now known to affect multiple other cellular signaling systems and hence they differentially participate in the regulation of the various cellular processes. The finding of several laboratories that SSTR-expressing tumors frequently contain two or more SSTR subtypes, and the recent discovery that SSTR subtypes might form homo/heterodimers to create a novel receptor with different functional characteristics, expand the array of selective SSTR activation pathways and subsequent intracellular signaling cascades. This may lead to improved clinical protocols that take into account possible synergistic interactions between the SSTR subtypes present on the same cancer cell. Radiolabeled sst analogs, such as [(111)In]-[diethylenetriamine pentaacetic acid (DTPA)-D-Phe(1)]-octreotide (OcreoScan), have proved to be very useful for tumor scintigraphy and internal radiotherapy of SSTR overexpressing tumors. The recent introduction of the metal chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) considerably improved the stability of the radioconjugates, making possible the incorporation of a variety of radionuclides, such as (90)Y for receptor-mediated radionuclide therapy or (68)Ga for positron emission tomography (PET). Another promising area is the development of sst conjugates incorporating cytotoxic anticancer drugs.

The clinical role of somatostatin analogues as antineoplastic agents: much ado about nothing?

BACKGROUND

Somatostatin (SST) analogues represent a novel approach for the treatment of certain cancers. The objective of this article is to summarise the current knowledge on SST analogues in the treatment of cancer patients.

METHODS

Computerised (Medline) and manual searches were performed to identify publications on clinical trials published in the English-speaking literature between 1966 and 2000. Information abstracted included patients' pre-treatment status, histology, SST receptor (SSTR) evaluation, type of SST analogue, application schedule and dose, duration of treatment, side-effects, response criteria applied (i.e. WHO response criteria, biochemical criteria or symptomatic investigations) and survival.

RESULTS

Our search disclosed 22 case reports, five phase 1 and 47 phase II trials, and eight randomised clinical trials using SST analogues (octreotide, lanreotide and vapreotide) as antineoplastic agents. With regard to the phase II trials, conflicting results have been demonstrated in almost all tumour entities investigated. The few randomised studies published so far have shown an impact on survival in patients with hepatocellular cancer, while the effect attributed to treatment in patients with gastrointestinal adenocarcinomas might well have been due to an exceptionally short survival in the control group. There appears to be evidence that SST analogues are able to enhance the therapeutic effects of hormonal intervention in patients with breast cancer, prostate cancer and probably pancreatic cancer. Interpretation of the findings, however, is complicated by the fact that patients were heavily pre-treated in some studies and response criteria have not been uniformly applied. In addition, most studies have not been designed to distinguish between receptor-mediated (direct) and indirect effects of SST analogues in tumour patients.

CONCLUSIONS

According to the results obtained so far, there can be no doubt about the wide therapeutic index and the high efficacy of SST analogues in the symptomatic management of neuroendocrine tumours. Apart from these indications, the data do not justify recommendation of SST analogues as antineoplastic agents outside of clinical trials, as the optimal dose and schedule of application for antineoplastic activity has not been defined for currently used agents. Carefully designed clinical trials including investigation of SSTR status before treatment, evaluation of an indirect mechanism of SST analogues, and assessment of optimal combination of hormone therapy and chemotherapy with SST analogues are clearly needed in the near future.

Combination of dexamethasone and a somatostatin analogue in the treatment of advanced prostate cancer

The local microenvironment at the sites of cancer metastases protects tumour cells from anticancer drug-induced apoptosis via mechanisms, such as soluble growth factors and cytokines. The concept of antisurvival factor (ASF) therapy as a component of anticancer treatments aims at neutralising the protective effect conferred upon cancer cells by the survival factor(s) derived by the local microenvironment, in order to enhance the sensitivity and/or reverse the resistance of tumour cells to other anticancer therapeutic strategies. Herein, we review the translation of this concept from ex vivo studies to clinical applications in the setting of prostate cancer refractory to androgen ablation (stage D3). At this stage, which predominantly involves bone metastases, insulin-like growth factor 1 (IGF-1) production (either growth hormone (GH)-dependent or GH-independent) can protect tumour cells from apoptosis, despite the significant suppression of androgens. The application of the ASF therapeutic concept involves the combination of dexamethasone (which suppresses GH-independent IGF-1) and somatostatin analogue (which suppresses endocrine, GH-dependent IGF-1) with the pro-apoptotic effect of the testicular androgen suppression by sustained use of LHRH analogues. In stage D3, patients who had failed anti-androgen withdrawal, chemotherapy and also had several other adverse prognostic features, the ASF-based combination achieved durable objective responses and major symptomatic improvement, paving the way for future applications of this approach. The ASF-based combination therapy illustrates a novel paradigm in cancer treatment: anti-tumour treatment strategies may not only aim at directly inducing cancer cell apoptosis, but can also target the tumour microenvironment and neutralise the protection it confers on metastatic cancer cells. The favourable toxicity profile of this therapeutic approach calls for its testing in a randomised controlled setting in metastatic prostate cancer and, conceivably, in other IGF-1-responsive malignancies.

Diagnosing and treating small-cell carcinomas of prostatic origin

PURPOSE

Small-cell carcinoma is very aggressive, metastasizes early and often, and does not respond to most chemotherapy regimens. In approximately 50% of cases of prostate cancer, tumors are a combination of small-cell carcinoma and androgen-sensitive adenocarcinoma. It is widely believed that no successful treatment exists for androgen-independent prostate cancer.

METHODS

A 67-year-old man had undergone androgen ablation therapy and radical prostatectomy for prostate cancer followed by bilateral orchiectomy, limited radiation therapy, and unsuccessful chemotherapy for pain-causing metastatic bone disease. Biopsy and immunohistochemical analysis revealed neuroendocrine differentiation of the cancer. The full extent of metastatic disease was assessed successfully using In-111, a somatostatin derivative. Octreotide acetate was used to treat the tumors.

RESULTS

In-111 OctreoScan scintigraphy was more sensitive in the diagnostic demonstration of metastatic foci than was bone scanning. Therapy with the cold somatostatin derivative resulted in a rapid and significant relief of pain with significant tumor shrinkage. The patient remained in remission for at least 10 weeks, when he was lost to follow-up.

CONCLUSIONS

Somatostatin analogs and their radionuclide and cytotoxic derivatives are recommended as adjuvant treatments for prostate carcinoma, especially in those patients who are at high risk for carcinoma recurrence after radical prostatectomy and who have advanced prostate carcinoma at the time of relapse. Because small-cell carcinomas of the prostate and lung are identical, these analogs may be useful in the detection and treatment of these tumors as well.

Effects of the somatostatin analog lanreotide on the circulating levels of chromogranin-A, prostate-specific antigen, and insulin-like growth factor-1 in advanced prostate cancer patients

BACKGROUND

The concept that neuroendocrine cells detected within prostate adenocarcinoma produce paracrine factors, that may exert a proliferative effect on exocrine prostate tumor cells, provides a rationale for the use of somatostatin analogs with the aim to counteract or delay the tumor progression. This study was designed to provide preliminary information on the effect of the administration of a long-acting somatostatin analog, lanreotide, on plasma levels of chromogranin A (CgA). Secondary aims were the evaluation of changes in circulating prostate-specific antigen (PSA) and insulin-like growth factor-1 (IGF-1).

METHODS

Lanreotide (Ipstyl 30 mg; Ipsen, Milan, Italy) was administered intramuscularly every 14 days for 2 months to nine heavily pretreated prostate cancer patients with hormone refractory disease. All patients had, at baseline conditions, CgA values above the normal range. Androgen deprivation was maintained during the study period, while other concomitant antineoplastic treatments were not allowed. Serum PSA levels and plasma CgA and IGF-1 values were measured every week.

RESULTS

Lanreotide treatment was very well tolerated and no patient experienced major toxicity. Plasma CgA values at baseline: mean 109 U/liter, standard deviation +/- 85 decreased significantly after treatment as follows: 42 U/liter, +/- 17.8; 27.2 U/liter +/- 13.6; 31.4 U/liter, +/- 17.8 and 27.6 U/liter, +/- 17.0; after 7, 14, 21, and 28 days, respectively (P < 0.01, Friedman ANOVA). Serum PSA did not change. Baseline IGF-1 was found to be above the detection limit in four cases, all of them showing a decrease after lanreotide.

CONCLUSIONS

Lanreotide administration to prostate cancer patients induces a decrease in plasma CgA and IGF-1 levels, without any influence on serum PSA values. Prostate 47:205-211, 2001.

High expression of somatostatin receptors and messenger ribonucleic acid for its receptor subtypes in organ-confined and locally advanced human prostate cancers

To evaluate the potential application of somatostatin (SST) analogs as an adjuvant treatment for prostate cancer, we characterized the binding sites for SST octapeptide analogs on prostate cancers in patients treated with radical prostatectomy. The affinity and density of binding sites for SST analog RC-160 on 80 surgical specimens of prostate cancers were determined by ligand competition assays. The expression of messenger ribonucleic acid (mRNA) for SST receptor subtype 1 (SSTR1), subtype 2 (SSTR2), and subtype 5 (SSTR5) was also investigated in 22 samples by RT-PCR. Fifty-two of 80 specimens (65%), showed a single class of specific binding sites for RC-160 with a mean dissociation constant (K(d)) of 9.44 nmol/L and a mean maximal binding capacity of 754.8 fmol/mg membrane protein. The mRNA for SSTR1 was detected in 86% of samples, whereas the incidences of mRNA for SSTR2 and SSTR5 were 14% and 64%, respectively. The expression of SSTR2 and/or SSTR5 was 100%, consistent with the presence of RC-160 binding. In patients at high risk of cancer recurrence (stage pT3 and/or Gleason score of 8-10), the incidence of RC-160 binding (65.7%) was similar to that observed in the low risk group (64.3%). The demonstration of the high incidence of octapeptide-preferring SSTRs in organ-confined and locally advanced prostate cancers supports the merit of further investigations of the application of SST analogs and their radionuclide and cytotoxic derivatives for adjuvant treatment of patients at high risk of cancer recurrence after radical prostatectomy. Such approaches could be also considered for patients with advanced prostate cancer at the time of relapse.

The effects of insulin-like growth factors on tumorigenesis and neoplastic growth

Several decades of basic and clinical research have demonstrated that there is an association between the insulin-like growth factors (IGFs) and neoplasia. We begin with a brief discussion of the function and regulation of expression of the IGFs, their receptors and the IGF-binding proteins (IGFBPs). A number of investigational interventional strategies targeting the GH or IGFs are then reviewed. Finally, we have assembled the available scientific knowledge about this relationship for each of the major tumor types. The tumors have been grouped together by organ system and for each of the major tumors, various key elements of the relationship between IGFs and tumor growth are discussed. Specifically these include the presence or absence of autocrine IGF-I and IGF-II production; presence or absence of IGF-I and IGF-II receptor expression; the expression and functions of the IGFBPs; in vitro and in vivo experiments involving therapeutic interventions; and available results from clinical trials evaluating the effect of GH/IGF axis down-regulation in various malignancies.

Microencapsulated octreotide pamoate in advanced gastrointestinal and pancreatic cancer: a phase I study

Fourteen patients suffering from advanced colorectal (n = 7), pancreatic (n = 4) or gastric (n = 3) carcinomas received treatment with microencapsulated octreotide pamoate 90 mg i.m. every 4 weeks (n = 4), 160 mg i.m. every 4 weeks (n = 4) or 160 mg i.m. every 2 weeks (n = 6). Two patients had stable disease, one for 4 and one for 6 months. Plasma insulin-like growth factor (IGF)-I decreased by 49-53%, IGF-II by 27-37% and total IGF-binding protein (IGFBP)-3 by 16-19%, whereas IGFBP-1 increased by 35-55%. Insulin and C-peptide levels decreased by 29-38% and 41-46% respectively. A non-significant decrease in urinary GH secretion and an increase in the ratio of fragmented to intact IGFBP-3 as well as IGFBP-3 protease activity was seen. The increase in IGFBP-3 fragmentation correlated negatively with alterations in IGF-I and IGF-II (P < 0.05). We conclude that microencapsulated octreotide administered in doses up to 160 mg every 2 weeks is well tolerated and has pronounced effects on several components of the IGF system in plasma. In addition, changes in IGFBP-3 protease activity because of cancer may contribute to alterations in IGF-I and -II, indicating the importance of measuring this parameter in addition to IGFs and IGFBPs when evaluating alterations in IGF-I.

Clinical uses of gut peptides

OBJECTIVE

The authors review clinical applications of gut-derived peptides as diagnostic and therapeutic agents.

SUMMARY BACKGROUND DATA

An increasing number of gut peptides have been evaluated for clinical use. Earlier uses as diagnostic agents have been complemented more recently by increasing application of gut peptides as therapeutic agents.

METHOD

The authors conducted a literature review.

RESULTS

Current experience with clinical use of gut peptides is described. Initial clinical applications focused on using secretomotor effects of gut peptides in diagnostic tests, many of which have now fallen into disuse. More recently, attention has been directed toward harnessing these secretomotor effects for therapeutic use in a variety of disorders, and also using the trophic effects of gut peptides to modulate gut mucosal growth in benign and malignant disease. Gut peptides have been evaluated in a variety of other clinical situations including use as adjuncts to imaging techniques, and modification of behaviors such as feeding and panic disorder.

CONCLUSIONS

Gut peptides have been used successfully in an increasing variety of clinical conditions. Further refinements in analogue and antagonist design are likely to lead to even more selective agents that may have important clinical applications. Further studies are needed to identity and evaluate these new agents.

A dose-finding study of lanreotide (a somatostatin analog) in patients with colorectal carcinoma

BACKGROUND

Laboratory data suggest that insulin-like growth factor-1 (IGF-1) may stimulate the growth of different human tumors. At least in acromegalic patients, somatostatin (SMS) analogs, such as lanreotide, suppress the serum levels of growth hormone (GH) and IGF-1.

METHODS

To evaluate the tolerability and biologic activity of different doses of lanreotide in patients with advanced colorectal carcinoma, consecutive groups of 3 patients each were subcutaneous treated with lanreotide at doses of 1, 2, 3, 4, 5, or 6 mg three times a day for 2 months. In the event of Grade 3 side effects, 3 additional patients were treated with the same dose before the next dose escalation. Serum samples were obtained on Days 0, 15, 30, and 60 for serum GH, IGF-1, and lanreotide assessment.

RESULTS

Twenty-four patients were enrolled and all were evaluable. Except for the 3 and 6 mg doses, for which the observation of a Grade 3 side effect required that an additional three patients be treated, it was sufficient to treat 3 patients at each dose. The overall incidence of side effects was as follows: changes in bowel habits, 83%; abdominal cramps, 79%; diarrhea, 17%; vomiting, 17%; nausea, 21%; steatorrhea, 78%; hyperglycemia, 35%; laboratory hypothyroidism, 39%; gallstones, 13%; and weight loss, 17%. No evidence of an increase in the incidence, intensity, or duration of side effects was observed with dose escalation. Serum IGF-1 levels were as follows: Day 15: 63%, 60%, and 67% of the baseline values for the low (1-2 mg), intermediate (3-4 mg), and high (5-6 mg) dose groups, respectively; Day 30: 63%, 59%, and 51%, respectively; and Day 60: 73%, 69%, and 47%, respectively. Serum lanreotide levels declined during treatment in all of the dose groups (90 ng/mL on Day 15, and 35 ng/mL on Day 60 for the 5-6 mg group; 10 ng/mL on Day 15, and 1.5 ng/mL on Day 60 for the 1-2 mg group). No antitumor activity or tumor marker reduction was observed.

CONCLUSIONS

No increase in toxicity was observed when subcutaneous lanreotide doses were escalated to 6 mg three times a day for 2 months. The highest doses seemed to maintain reduced serum IGF-1 levels; with the lowest doses, a "rebound" in serum IGF-1 levels was observed during treatment. Nevertheless, intermittent subcutaneous injections do not ensure constant serum drug concentrations over time.