Small-cell neuroendocrine carcinoma of the prostate: are heterotransplants a better experimental model?

Preclinical Models of Neuroendocrine Neoplasia

Neuroendocrine neoplasia (NENs) are a complex and heterogeneous group of cancers that can arise from neuroendocrine tissues throughout the body and differentiate them from other tumors. Their low incidence and high diversity make many of them orphan conditions characterized by a low incidence and few dedicated clinical trials. Study of the molecular and genetic nature of these diseases is limited in comparison to more common cancers and more dependent on preclinical models, including both in vitro models (such as cell lines and 3D models) and in vivo models (such as patient derived xenografts (PDXs) and genetically-engineered mouse models (GEMMs)). While preclinical models do not fully recapitulate the nature of these cancers in patients, they are useful tools in investigation of the basic biology and early-stage investigation for evaluation of treatments for these cancers. We review available preclinical models for each type of NEN and discuss their history as well as their current use and translation.

Small-cell carcinoma of the prostate with negative CD56, NSE, Syn, and CgA indicators: A case report

BACKGROUND

Small-cell carcinoma of the prostate (SCCP) is a clinically rare malignant tumor, accounting for < 1% of all prostate tumors. However, negativity for all SCCP neuroendocrine markers is rare. Herein, we report a case of SCCP with completely negative neuroendocrine markers and explore its clinicopathologic features, thus improving the understanding of its clinical diagnosis and management.

CASE SUMMARY

We report the case of a 48-year-old patient with SCCP negative for common sensitive neuroendocrine-staining indicators. Dysuria was the first symptom, and rectal examination revealed a hard prostate, palpable nodules, diffuse prostate enlargement, no pressure pain, no blood staining in the finger sleeve, 1.33 ng/mL total prostate-specific antigen level, and a free-to-total prostate-specific antigen ratio of 0.21 ng/mL. Ultrasound suggested a prostate size of 5.3 cm × 5.8 cm × 5.6 cm, and magnetic resonance imaging suggested prostate cancer. The lower posterior bladder wall, rectal mesentery, and bilateral seminal vesicles were invaded, with multiple lymph node metastases in the pelvis. A whole-body bone scan suggested an abnormally active multiple bone metabolism and possible bone metastases. Head and lungs computed tomography revealed no significant nodal shadow. Following a pathological diagnosis of SCCP after a prostate puncture, with negative indicators of common sensitive neuroendocrine staining, chemotherapy was administered; the patient died 4-5 mo after SCCP diagnosis.

CONCLUSION

SCCP is a rare disease characterized by atypical clinical symptoms, limited treatment options, a short survival period, and a poor prognosis.

Small cell carcinoma of the prostate presenting with skin metastasis: a case report

INTRODUCTION

Small cell carcinoma of the prostate is a very rare and aggressive type of prostatic cancer. Most cases are diagnosed at advanced stage due to early metastasis. The bones, liver, regional and distant lymph nodes are the most common sites of metastasis of small cell carcinoma of the prostate. Skin metastasis of small cell carcinoma of the prostate is a very rare entity due to the uncommon metastatic site. Here, we describe the case of a patient with small cell carcinoma of the prostate which metastasized to his skin.

CASE PRESENTATION

A 74-year-old Caucasian man presented to another urology center for mild lower urinary tract symptoms in 2003. His prostate-specific antigen was 23 ng/mL. According to the physical examination signs and prostate-specific antigen, he underwent a transrectal ultrasound-guided prostate biopsy. The pathologic examination of his prostate revealed a Gleason score: 3 + 4 = 7 adenocarcinoma of the prostate. Investigations showed stage T2N0M0 disease and he was treated with radiotherapy to his pelvic lymph nodes and prostate. Six years after the initial diagnosis, he complained of a palpable left-side 2 × 2 cm subcutaneous solitary mass localized just behind his scapula. The results of his laboratory tests including serum acid phosphatase and prostate-specific antigen were in normal ranges. Our general surgery department performed a diagnostic biopsy of the mass and totally excised the lesion. The pathologic examination of the mass showed small cell carcinoma metastasis with chromogranin + and the pathologist advised us to examine the lung or prostate for the primary tumor. The patient undertook a transrectal ultrasound-guided prostate biopsy and the pathologic result revealed small cell carcinoma within residual adenocarcinoma. We investigated the other sites for metastasis and restaging investigations showed a 1cm metastatic lesion in his liver. Our medical oncology department decided to treat him with combination chemotherapy with etoposide and cisplatin in six cycles; however, he died due to disseminated myocardial infarction before starting the fifth combination chemotherapy cycle.

CONCLUSIONS

Clinicians should keep in mind that early diagnosis of this disease is very difficult due to early metastatic spread of small cell carcinoma and lack of concordant elevation of prostate-specific antigen. There is no accepted standard treatment modality for this pathology and overall prognosis is poor.

In vivo safety and antitumor efficacy of bifunctional small hairpin RNAs specific for the human Stathmin 1 oncoprotein

Bifunctional small hairpin RNAs (bi-shRNAs) are functional miRNA/siRNA composites that are optimized for posttranscriptional gene silencing through concurrent mRNA cleavage-dependent and -independent mechanisms (Rao et al., 2010 ). We have generated a novel bi-shRNA using the miR30 scaffold that is highly effective for knockdown of human stathmin (STMN1) mRNA. STMN1 overexpression well documented in human solid cancers correlates with their poor prognosis. Transfection with the bi-shSTMN1-encoding expression plasmid (pbi-shSTMN1) markedly reduced CCL-247 human colorectal cancer and SK-Mel-28 melanoma cell growth in vitro (Rao et al., 2010 ). We now examine in vivo the antitumor efficacy of this RNA interference-based approach with human tumor xenografted athymic mice. A single intratumoral (IT) injection of pbi-shSTMN1 (8 μg) reduced CCL-247 tumor xenograft growth by 44% at 7 days when delivered as a 1,2-dioleoyl-3-trimethyl-ammoniopropane:cholesterol liposomal complex. Extended growth reductions (57% at day 15; p < 0.05) were achieved with three daily treatments of the same construct. STMN1 protein reduction was confirmed by immunoblot analysis. IT treatments with pbi-shSTMN1 similarly inhibited the growth of tumorgrafts derived from low-passage primary melanoma (≥70% reduction for 2 weeks) and abrogated osteosarcoma tumorgraft growth, with the mature bi-shRNA effector molecule detectable for up to 16 days after last injection. Antitumor efficacy was evident for up to 25 days posttreatment in the melanoma tumorgraft model. The maximum tolerated dose by IT injection of >92 μg (Human equivalent dose [HED] of >0.3 mg/kg) in CCL-247 tumor xenograft-bearing athymic mice was ∼10-fold higher than the extrapolated IC(50) of 9 μg (HED of 0.03 mg/kg). Healthy, immunocompetent rats were used as biorelevant models for systemic safety assessments. The observed maximum tolerated dose of <100 μg for intravenously injected pbi-shSTMN1 (mouse equivalent of <26.5 μg; HED of <0.09 mg/kg) confirmed systemic safety of the therapeutic dose, hence supporting early-phase assessments of clinical safety and preliminary efficacy.

Use of irinotecan for treatment of small cell carcinoma of the prostate

BACKGROUND

Prostatic small cell carcinoma (SCC) is a rare variant of prostate cancer. It is extremely aggressive and resistant to available therapies with a median survival range of 5-17 months. No standard chemotherapeutic regimen has been established for its treatment. In search of a new therapeutic approach, we examined the response of patient-derived prostatic SCC tissue xenografts to irinotecan, a topoisomerase I inhibitor.

METHODS

A tumor tissue line was established from a patient's prostatic SCC by subrenal capsule grafting using NOD-SCID mice. Mice carrying subcutaneous transplants of the tumor line were then treated for 2 weeks with irinotecan alone and in combination with cisplatin. The effect on tumor volume, histopathology, and apoptosis were determined.

RESULTS

The prostatic SCC tissue line resembled the donor tissue in morphologic and immunohistochemical features. Irinotecan (20 mg/kg/day; days 1-3, 8-10) completely arrested xenograft growth with a small reduction in tumor volume and only minor weight loss of the hosts (7%); irinotecan (12 mg/kg; same schedule) + cisplatin (2.5 mg/kg/day; days 1 and 8) had a similar effect, but with lower weight loss. While the growth inhibition involved apoptosis, it was also associated with a marked increase in autophagy.

CONCLUSIONS

Tumor tissue lines established via subrenal capsule xenografting provide models with clinical relevance and the present study suggests that irinotecan could be useful for therapy of refractory prostatic SCC, in particular in combination with cisplatin.