Lack of c-kit exon 11 activating mutations in c-KIT/CD117-positive SCLC tumour specimens

Imatinib in c-KIT-mutated metastatic solid tumors: A multicenter trial of Korean Cancer Study Group (UN18-05 Trial)

INTRODUCTION

We conducted an open-label, single-arm, multi-center phase II trial to evaluate the efficacy and safety of imatinib chemotherapy-refractory or metastatic solid tumor patients with c-KIT mutations and/or amplification.

METHODS

c-KIT mutations and amplification were detected using NGS. Imatinib (400 mg daily) was administered continuously in 28-day cycles until disease progression, unacceptable adverse events, or death by any cause. The primary endpoint was the objective response rate (ORR).

RESULT

In total, 18 patients were enrolled on this trial. The most common tumor type was melanoma (n = 15, 83.3%), followed by ovarian cancer, breast cancer, and metastasis of unknown origin (MUO) (each n = 1, 5.5%). The total number of evaluable patients was 17, of which one patient had a complete response, six patients had partial response, and two patients had stable disease. The overall response rate (ORR) of 41.2% (95% CI 17.80-64.60) and a disease control rate of 52.9% (95% CI 29.17-76.63). The median progression-free survival was 2.2 months (95% CI 1.29-3.20), and median overall survival was 9.1 months (95% CI 2.10-16.11). The most common adverse events were edema (31.3%), anorexia (25.0%), nausea (18.8%), and skin rash (18.8%).

CONCLUSION

Imatinib demonstrated modest anti-tumor activity and a manageable safety profile in chemotherapy-refractory solid tumors with c-KIT mutation, especially in melanoma patients.

Small-Cell Lung Cancer-An Update on Targeted and Immunotherapies

Small-cell lung cancer (SCLC) is an aggressive disease with distinct biological and clinical features. The clinical course of SCLC is generally characterised by initial sensitivity to DNA-damaging therapies, followed by early relapse and broad cross resistance to second line agents. Whilst there has been an enormous expansion of effective targeted and immune-based therapeutic options for non-small cell lung cancer (NSCLC) in the last decade, little improvement has been achieved in SCLC treatment and survival due, at least in part, to underappreciated inter- and intra-tumoral heterogeneity. Here we review the current treatment paradigm of SCLC including recent advances made in utilizing immunotherapy and the challenges of identifying a predictive biomarker for immunotherapy response. We examine emerging new targeted therapies, combination immunotherapy and future directions of SCLC treatment research.

Small Cell Carcinoma of the Urinary Bladder: KIT and PDGFRA Gene Mutations

Primary small cell carcinoma of the urinary bladder is very rare. A 72-year-old was admitted to our hospital because of hematuria and dysuria. Cystoscopy revealed a bladder full of multiple, solid and papillary tumors. Biopsies from the deep and papillary tumors were taken. Histologically, tumor was pure small cell carcinoma. Immunohistochemically, the tumor cells were positive for cytokeratin, chromo-granin, synaptophysin, neuron-specific enolase, CD56, CD117 and Ki67 (labeling 70%). The tumor cells were negative for CK7, CK20, CD3, CD20, LCA, CDX2, uroplakin, thyroid transcription factor 1, PSA and p63. Metastatic workup was performed an no primary or metastatic lung lesions were noted. Due to the clinical, radiologic and immunohistochemical findings, the patient was diagnosed as primary small cell carcinoma of bladder. A molecular genetic analysis for KIT (exons 9, 11, 13 and 17) and PDGFRA (exons 12 and 18) genes was performed, in paraffin micro dissection specimens, by the PCR-direct sequencing method. According to the sequencing analyses, two mutations were found at positions 558 (p.K558N) and 562 (p.E562D) in KIT gene exon 11 in our case. The another hand the same case presented two mutations in PDGFRA gene exon 14 at position 631 (p.P631A) and 638 (p.638Q_639AinsC). The disease process was fulminant and the patient was lost due to several complications prior to any chemotherapy.

Detection of c-kit mutational status in small-cell lung cancer in a Chinese cohort

BACKGROUND

Overexpression of KIT (CD117), a tyrosine kinase receptor, and its natural ligand, stem cell factor, are found in small-cell lung cancer (SCLC). Somatic mutations of the proto-oncogene c-kit constitutively activate KIT expression in a ligand-independent way. To explore the clinical value of the c-kit mutation as a potential target for therapy with tyrosine kinase inhibitors, the c-kit mutational status and KIT expression in tumors from Chinese patients with SCLC were analyzed.

METHODS

Using 107 paraffin-embedded SCLC tumor specimens, c-kit exons 9, 11, 13, and 17 were analyzed for mutations by polymerase chain reaction and direct sequencing.

RESULTS

There were no activating mutations in exons 9, 11, 13, or 17. However, a point mutation in intron 16 (81240 G>A) was found in 11 out of the 107 samples (10.3%), of which the majority were limited-stage SCLC (10/11, 90.9%). Immunohistochemical staining of tumors harboring the c-kit point mutation using the anti-CD117 antibody showed that the mutation status was not associated with the expression of KIT.

CONCLUSION

These findings indicate that the incidence and the types of c-kit mutations in SCLC tumors found in Chinese are different from those of the Caucasian population. Nevertheless, c-kit mutations are similarly rare in both groups, implying that they may not be suitable targets for c-kit-based tyrosine kinase inhibitors.

Therapeutic efficacy of c-kit-targeted radioimmunotherapy using 90Y-labeled anti-c-kit antibodies in a mouse model of small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive tumor and prognosis remains poor. Therefore, the development of more effective therapy is needed. We previously reported that high levels of an anti-c-kit antibody (12A8) accumulated in SCLC xenografts. In the present study, we evaluated the efficacy of two antibodies (12A8 and 67A2) for radioimmunotherapy (RIT) of an SCLC mouse model by labeling with the (90)Y isotope.

METHODS

(111)In- or (125)I-labeled antibodies were evaluated in vitro by cell binding, competitive inhibition and cellular internalization assays in c-kit-expressing SY cells and in vivo by biodistribution in SY-bearing mice. Therapeutic efficacy of (90)Y-labeled antibodies was evaluated in SY-bearing mice upto day 28 and histological analysis was conducted at day 7.

RESULTS

[(111)In]12A8 and [(111)In]67A2 specifically bound to SY cells with high affinity (8.0 and 1.9 nM, respectively). 67A2 was internalized similar to 12A8. High levels of [(111)In]12A8 and [(111)In]67A2 accumulated in tumors, but not in major organs. [(111)In]67A2 uptake by the tumor was 1.7 times higher than for [(111)In]12A8. [(90)Y]12A8, but not [(90)Y]67A2, suppressed tumor growth in a dose-dependent manner. Tumors treated with 3.7 MBq of [(90)Y]12A8, and 1.85 and 3.7 MBq of [(90)Y]67A2 (absorbed doses were 21.0, 18.0 and 35.9 Gy, respectively) almost completely disappeared approximately 2 weeks after injection, and regrowth was not observed except for in one mouse treated with 1.85 MBq [(90)Y]67A2. The area of necrosis and fibrosis increased depending on the RIT effect. Apoptotic cell numbers increased with increased doses of [(90)Y]12A8, whereas no dose-dependent increase was observed following [(90)Y]67A2 treatment. Body weight was temporarily reduced but all mice tolerated the RIT experiments well.

CONCLUSION

Treatment with [(90)Y]12A8 and [(90)Y]67A2 achieved a complete therapeutic response when SY tumors received an absorbed dose greater than 18 Gy and thus are promising RIT agents for metastatic SCLC cells at distant sites.

Small cell neuroendocrine carcinoma of the prostate: incidence and a report of four cases with an examination of KIT and PDGFRA

Because there have been no reports on the incidence and expressions and mutations of KIT and PDGFRA in small cell neuroendocrine carcinoma (SCNEC) of the prostate, the author surveyed archival specimens of 2,642 prostatic specimens (biopsy, 1,503 cases; transurethral resection, 1,009 cases; prostatectomy, 130 cases). Of these, 706 cases were malignant tumors. In equivocal cases (n = 16) of Gleason 5 adenocarcinoma resembling SCNEC, several neuroendocrine markers were immunohistochemically examined. As the results, four cases of SCNEC were identified; therefore the incidence of SCNEC was 0.5% of all prostatic malignancies. All the four cases were biopsies. The remaining 686 cases were adenocarcinomas. In case 1 (50 years of age), the SCNEC tumor cells were positive for cytokeratin, P504S, synaptophysin, KIT, and PDGFRA, but negative for PSA, neuron specific enolase, CD56, and TTF-1. In case 2 (70 years of age), the tumor cells were positive for cytokeratin, PSA, P504S, chromogranin, and synaptophysin, but negative for neuron-specific enolase, CD56, TTF-1, KIT, and PDGFRA. In case 3 (72 years of age), the SCNEC tumor cells were positive for cytokeratin, PSA, P504S, synaptophysin, CD56, KIT, and PDGFRA, but negative for neuron-specific enolase, chromogranin, and TTF-1. In case 4 (81 years of age), the SCNEC tumor cell were positive for cytokeratin, PSA, P504S, chromogranin, synaptophysin, neuron-specific enolase, KIT, and PDGFRA, but negative for CD56 and TTF-1. A molecular genetic analysis using PCR-direct sequencing showed no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes in three informative cases of SCNEC. The present cases were the first of prostatic SCNEC with an examination of KIT and PDGFRA expression and KIT and PDFGRA gene mutations.

Esophageal combined carcinomas: Immunohoistochemical and molecular genetic studies

Primary esophageal combined carcinoma is very rare. The authors herein report 2 cases. Case 1 was a combined squamous cell carcinoma and small cell carcinoma, and case 2 was a combined squamous cell carcinoma, adenocarcinoma, and small cell carcinoma. Case 1 was a 67-year-old man with complaints of dysphagia. Endoscopic examination revealed an ulcerated tumor in the middle esophagus, and 6 biopsies were obtained. All 6 biopsies revealed a mixture of squamous cell carcinoma and small cell carcinoma. Both elements were positive for cytokeratin, epithelial membrane antigen, and p53 protein, and had high Ki-67 labeling. The small cell carcinoma element was positive for synaptophysin, CD56, KIT, and platelet-derived growth factor-α (PDGFRA), while the squamous cell carcinoma element was not. Genetically, no mutations of KIT and PDGFRA were recognized. The patient died of systemic carcinomatosis 15 mo after presentation. Case 2 was a 74-year-old man presenting with dysplasia. Endoscopy revealed a polypoid tumor in the distal esophagus. Seven biopsies were taken, and 6 showed a mixture of squamous cell carcinoma, small cell carcinoma, and adenocarcinoma. The 3 elements were positive for cytokeratins, epithelial membrane antigen, and p53 protein, and had high Ki-67 labeling. The adenocarcinoma element was positive for mucins. The small cell carcinoma element was positive for CD56, synaptophysin, KIT, and PDGFRA, but the other elements were not. Mutations of KIT and PDGFRA were not recognized. The patient died of systemic carcinomatosis 7 mo after presentation. These combined carcinomas may arise from enterochromaffin cells or totipotential stem cell in the esophagus or transdifferentiation of one element to another. A review of the literature was performed.

Phase II cancer prevention clinical trials

The development of agents to prevent cancer requires an iterative process of target identification, preclinical testing, and early and late phase clinical trials to establish efficacy and safety. Since phase III definitive efficacy trials with cancer endpoints require a lengthy timeframe and considerable resources for completion, it is critical to first optimize agent delivery and trial design and to determine preliminary efficacy via the conduct of phase II trials. Phase II trials vary considerably in their endpoints, cohorts, and designs due to differences in the process of carcinogenesis and ability to sample tissues across different target organs. However, the goal of all such trials is to provide evidence of interference with the development of cancer and to identify safety signals that would limit the benefit from interventions.

Large cell neuroendocrine carcinoma with sarcomatous changes of the endometrium: a case report with immunohistochemical studies and molecular genetic study of KIT and PDGFRA

The author herein reports a very rare case of large cell neuroendocrine carcinoma (LCNEC) with sarcomatous changes of the endometrium. A 40-year-old woman was admitted to our hospital because of abnormal uterine bleeding. Gynecologic examination and imaging modalities revealed a polypoid tumor of the uterine corpus. Uterine curettage biopsy revealed a sarcomatous undifferentiated carcinoma. Simple hysterectomy, salpingo-oophorectomy, extensive lymph node dissection, and omentectomy were performed. The patient was diagnosed as having FIGO stage Ib (T1N0M0) carcinoma, and adjuvant chemotherapy was performed. The patient is now alive 16 months after the operation. Pathologically, a polypoid tumor measuring 3x2x2 cm(3) was found in the uterine corpus. Histologically, the tumor consisted of relatively large-sized carcinoma cells without differentiation. The tumor cells have abundant cytoplasm and prominent nucleoli. It was composed of a spindle cell component (40%) and an epithelioid component (60%). A gradual transition between the two was recognized. Immunohistochemically, both elements showed the same immunophenotypes. The carcinoma cells were positive for cytokeratin, vimentin, CA125, CD34, estrogen receptor, progesterone receptor, p53 protein, Ki-67 antigen (80%), synaptophysin, CD56, KIT, and PDGFRA. They were negative for epithelial membrane antigen, CEA, desmin, S100 protein, melanosome, alpha-smooth muscle actin, chromogranin, and neuron-specific enolase. A molecular genetic analysis revealed no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes. The final diagnosis was LCNEC with sarcomatous changes.

KIT-positive primary small cell carcinoma of the endometrium: a case report with immunohistochemical and molecular genetic analysis of KIT and PDGFRA genes

BACKGROUND

Primary small cell carcinoma of the endometrium is very rare, and there have been no reports on KIT and PDGFRA in endometrial small cell carcinoma.

CASE REPORT

An 87-year-old woman was admitted to our hospital because of genital bleeding. Endometrial cytology and biopsy revealed small cell carcinoma. Scrutiny of the body showed stage III endometrial carcinoma with metastases. An immunohistochemical study of the biopsy specimens revealed positive reactions for synaptophysin, CD56, KIT, and PDGFRA, and negative reactions for cytokeratins, neuron-specific enolase, and chromogranin. A molecular genetic analysis using PCR-direct sequencing identified no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes. The patient received chemotherapy and radiation, but showed a downhill course, and died of carcinomatosis 6 months after the initial presentation.

CONCLUSION

The present case is the first reported case of primary small cell carcinoma of the endometrium with an examination of KIT and PDGFRA expressions and KIT and PDFGRA gene mutations.

Primary small cell carcinoma of the pleura: a case report with immunohistochemical and molecular genetic analyses of KIT and PDGFRA genes

An extremely rare case of primary small cell carcinoma of the pleura with an emphasis on KIT and platelet-derived growth factor receptor-α (PDGFRA) genes is reported here. A 67-year-old man underwent left testicular orchiectomy because of a testicular tumor. The tumor was immunohistochemically shown to be diffuse large B-cell lymphoma. The patient was treated with chemotherapy and radiation and followed up in our hospital. Eight years after the orchiectomy, the patient (75 years old) developed left pleural tumor and pleural effusion, and a biopsy was performed. The biopsy revealed a medullary malignant tumor consisting of small round and spindle cells. The following three possibilities were considered: recurrent lymphoma, mesothelioma, and small cell carcinoma. Immunohistochemically, the tumor cells were positive for cytokeratin, synaptophysin, CD56, KIT, and PDGFRA, but negative for CEA, cytokeratin 5/6, neuron-specific enolase, chromogranin, CD45, CD3, CD20, CD45RO, CD15, CD30, calretinin, WT-1, B72.3, D2-40, and TTF-1. Therefore, a diagnosis of pleural small cell carcinoma was made. A molecular genetic analysis using PCR-direct sequencing identified no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes. The patient was treated with chemotherapy (cisplatin) and radiation (50 Gray). The present case is the first reported case of primary small cell carcinoma of the pleura with an examination of KIT and PDGFRA expressions and KIT and PDGFRA gene mutations.

Autopsy case of primary small cell carcinoma of the urinary bladder: KIT and PDGFRA expression and mutations

The author reports a rare autopsy case of primary small cell carcinoma of the urinary bladder with an emphasis on KIT and platelet-derived growth factor receptor-alpha (PDGFRA) genes. An 81-year-old man was admitted to Shizuoka City Shimizu Hospital because of dysuria. Cytology of the urine showed small carcinoma cells. Transurethral bladder tumorectomy indicated small cell carcinoma, and the patient was treated by radiation and chemotherapy. The patient died, however, of systemic metastasis 2 months after the first presentation. An autopsy showed a bladder small cell carcinoma and it systemic metastasis. Immunohistochemistry of the tumorectomy and autopsy specimens was positive for cytokeratins, neuron-specific enolase, synaptophysin, CD56, KIT and PDGFRA, and negative for chromogranin and thyroid transcriptional factor-1. Polymerase chain reaction-direct sequencing showed no mutations of KIT (exons 9, 11, 13 and 17) or PDGFRA (exons 12 and 18) genes in the tumorectomy specimens and was non-contributory due to DNA damage in autopsy specimens. The present case is the first case of primary small cell carcinoma of the urinary bladder involving examination of KIT and PDGFRA expression and KIT and PDGFRA gene mutations.

Primary small cell carcinoma of the mediastinum: a case report with immunohistochemical and molecular genetic analyses of KIT and PDGFRA genes

The author reports herein an extremely rare case of primary small cell carcinoma of the mediastinum with an emphasis on KIT and PDGFRA genes. A 66-year-old man was found to have a mediastinal tumor on a routine chest X-ray examination, and was admitted to our hospital. Imaging modalities revealed a 5 x 4 cm tumor in the middle mediastinum near the bronchial carina. No other tumors were detected in the body including the lungs. Video-assisted thoracoscopy confirmed the mediastinal tumor, and a large incisional biopsy was performed. The tumor was histologically small cell carcinoma. An immunohistochemical study revealed positive reactions for cytokeratins (AE1/3, polyclonal), synaptophysin, neuron-specific enolase, CD56, KIT, and PDGFRA, and negative reactions for chromogranin, CEA, CD45, CD20, and CD3. Ki-67 labeling showed a value of 80%. A molecular genetic analysis using PCR-direct sequencing identified no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes. The patient received radiation and chemotherapy, and the tumor was fully resolved. The patient has remained free of recurrence for 6 years after the first presentation. The present case is the first reported case of primary small cell carcinoma of the mediastinum with an examination of KIT and PDGFRA expressions and KIT and PDFGRA gene mutations.

Primer: first do no harm--when is it appropriate to plan a cancer prevention clinical trial?

Abundant preclinical and clinical data suggest that cancer is a preventable disease; however, few, if any, of the medical interventions available are completely without adverse effects or risk to the patient. This statement is especially true with regard to phenotypically healthy but high-risk populations. Balancing the risks from interventions with the risk of future life-threatening disease is particularly challenging because no standardized methodologies to perform such calculations exist. It is critical, therefore, to establish a framework for determining when interventions show sufficient promise of efficacy and sufficient safety to justify their testing in clinical trials. Systematic review of all available preclinical, epidemiological, and clinical data, along with a mechanistic understanding of the biology of the disease under study, is mandatory before clinical trials are embarked upon. This Review identifies the issues that are critical for decision-making when clinical trials in human beings are being contemplated and provides a framework that can be applied in making these decisions.

Targeting c-KIT, PDGFR in cancer of unknown primary: a screening study for molecular markers of benefit

AIMS

In view of available targeted therapies, we investigated the presence of c-kit, PDGFR gene mutations and protein expression in cancer of unknown primary (CUP) in order to study their contribution in pathogenesis, their prognostic value and potential as therapeutic targets.

METHODS

Mutations in hot spots c-kit exon 11 and PDGFR exons 12 and 18 were studied in paraffin-embedded tumour samples from 50 patients with CUP by means of PCR-based single-strand conformational polymorphism and protein expression by means of streptavidin-biotin immunoperoxidase assays. Molecular markers were screened for possible correlations with patient outcome.

RESULTS

No shifted band was detected in any of the polyacrylamide gel electrophoreses, indicating absence of c-kit exon 11 and PDGFR exon 12, 18 mutations. Immunohistochemical analysis in 37 tumours revealed positive membranous CD117 expression in 30 samples (81%) of which five exhibited strong (+3), four moderate (+2) and 21 weak (+1) staining. PDGFRa protein staining was seen in 15 out of 30 (50%) cases, mostly weak (13) and rarely moderate (1) or strong (1). The expression of KIT or PDGFRa protein did not correlate with the clinical outcome of the patients in our cohort.

CONCLUSIONS

In a moderate-sized CUP patient cohort, KIT or PDGFRa protein overexpression is rare, does not have gross prognostic significance for survival and is not associated with presence of activating mutations.

Current status of second-line treatment and novel therapies for small cell lung cancer

Despite high response rates to first-line standard treatment, the great majority of patients with small cell lung cancer (SCLC) will relapse and succumb to their disease rather quickly. In the context of salvage therapy, symptom palliation and quality-of-life improvements, besides survival prolongation, are primary treatment endpoints. A variety of single-agent and multi-agent chemotherapy regimens have been tested with limited success in patients with recurrent SCLC. A number of combination regimens have demonstrated high response rates in second-line settings, but these can be considered only for patients with good performance status. Treatment outcome depends on many factors, including type of response to first-line therapy, treatment-free interval, and performance status. Currently, topotecan represents an effective, tolerable therapeutic option and is the only agent approved for this indication. The management of patients with recurrent disease remains an area of active research. This review provides an update of clinical research on second-line chemotherapy of SCLC and of recent results obtained with novel molecular targeted approaches in both first- and second-line therapy.

Prognostic value of KIT expression in small cell lung cancer

BACKGROUND

Small cell lung cancer (SCLC) is a very aggressive disease, with poor survival rates despite standard treatment with combination chemotherapy with or without radiotherapy. Further insights into the molecular biology of this malignant tumour are needed to improve the therapeutic approaches and outcome. KIT protein is expressed in SCLC, and its kinase activity has been implicated in the pathophysiology of many tumours, including SCLC. The purpose of this study was to evaluate the prevalence of KIT expression in patients with SCLC and its prognostic value.

METHODS

We performed an inmunohistochemical analysis of 204 SCLC samples to determine KIT protein expression. The relationship between KIT expression and clinicopathological parameters was evaluated. Univariate and multivariate analyses were performed to define its prognostic significance.

RESULTS

KIT expression was observed in 149 of 204 tumour tissues (73%). KIT expression was associated with advanced disease and with decreased incidence of bone metastases. No significant differences were observed for time to disease progression (TTP) (9.1% versus 6.2% at 3 years, p=0.6) or overall survival (OS) (10.7% versus 6.9% at 3 years, p=0.37) among patients with KIT positive versus negative tumours, respectively. Multivariate analysis showed that sex, tumour stage, albumin levels and response to therapy were the only independent predictors for survival.

CONCLUSION

KIT protein is expressed in a high percentage of SCLC tumours. In our study population, however, the expression of KIT had no significant impact on survival.

PDGFR-beta expression in small cell lung cancer patients

BACKGROUND

Platelet derived growth factor (PDGF) and PDGFR-beta are expressed and have been found to have prognostic value in several human cancers. Data in non-small-cell cancer cell lines have suggested that PDGFR is a therapeutic target for drug development. In the current study PDGFR-beta expression and prognostic value in small cell lung cancer (SCLC) was investigated.

METHODS AND MATERIALS

Paraffin-embedded tissue blocks from 53 patients with limited and extensive stage SCLC were obtained for immunohistochemical staining. Tumors from each patient were sampled 3 times and stained with PDGFR-beta specific antibody. Patients were divided into low and high staining groups based on intensity.

RESULTS

There was high intensity PDGFR-beta staining in 20 patients with SCLC. Another 29 expressed low intensity PDGFR-beta staining, with only 4 patients showing no PDGFR-beta staining. There was no statistically significant difference in 5 year overall survival between patients with low levels of PDGFR-beta staining vs. those with high level staining SCLC tumors (p = 0.538).

CONCLUSIONS

The present study found that the majority of SCLC patients express, at least, a low level of PDGF-beta. However, the level of PDGFR-beta expression was not a statistically significant predictor of 5 year overall survival in SCLC.

Small cell lung cancer

Small cell lung cancer accounts for 13-15% of all lung cancer worldwide. There has been a decrease in the number of cases, with no clear explanation, except probably to changing in smoking habits in the last two decades. In the early eighties, it became clear that SCLC was an extremely sensitive tumor as to radiation as to chemotheraputic agents. With cisplatinum etoposide combinations or cyclophosphamide, anthracycline and vincristine/etyoposide regimens responses were observed in 50-70%, with 20-30% complete remissions in extensive disease. For limited stage patients chemotherapy associated with thoracic radiation was able to produce a cure rate of 10-20%. The addition of prophylactic brain irradiation to limited stage cases has reduced mortality by a factor of nearly 5%. But despite these early good results no breakthrough came later on, and in the last decade or so, we are still facing this plateau. New agents have recently been included in the therapeutic armamentarium, such as gemcitabine, irinotecan, paclitaxel. This fact has allowed many patients to receive a relatively active second line therapy, but the overall survival remains unchanged. Targeted therapies are undergoing some evaluations, but the data are too premature and so far quite discouraging. At the present time there is a urgent need to improve clinical research in this somehow forgotten disease.

Analysis of c-kit expression in small cell lung cancer: prevalence and prognostic implications

c-kit, a growth factor receptor with tyrosine kinase activity, plays an important role in the biology of cancer. Its expression has been documented in several malignancies. We performed a retrospective study in 85 patients diagnosed with small cell lung cancer (SCLC) to determine the prevalence and role of c-kit as a possible prognostic marker in this lung cancer malignancy. Demographic and clinical data were obtained from patient charts. c-kit, analyzed as immunohistochemical expression in paraffin-embedded tumour tissues, was observed in 60% of patients. All patients were former or present smokers. At diagnosis, 46% of the patients had limited disease (LD) and 54% extended disease (ED). c-kit expression was observed in 59% of LD and 61% of ED patients (p=0.4). Patients received a median of 4 cycles first-line combination chemotherapy (platinum and etoposide). In LD patients, time to progression (TTP) was 11.5 months in c-kit (+) versus 5.9 in c-kit (-) patients (p=0.14), and median survival 15.4 and 12.8 months, respectively (p=0.33). In the ED group, TTP was 5.5 months in c-kit (+) versus 3.8 in c-kit (-) patients (p=0.34), whereas median survival was 6.3 and 7.9 months, respectively (p=0.45). With the limited number of patients in mind, our findings tended towards an association between c-kit expression and survival in the LD group.

KIT (CD117): a review on expression in normal and neoplastic tissues, and mutations and their clinicopathologic correlation

CD117 (KIT) is a type III receptor tyrosine kinase operating in cell signal transduction in several cell types. Normally KIT is activated (phosphorylated) by binding of its ligand, the stem cell factor. This leads to a phosphorylation cascade ultimately activating various transcription factors in different cell types. Such activation regulates apoptosis, cell differentiation, proliferation, chemotaxis, and cell adhesion. KIT-dependent cell types include mast cells, some hematopoietic stem cells, germ cells, melanocytes, and Cajal cells of the gastrointestinal tract, and neoplasms of these cells are examples of KIT-positive tumors. Other KIT-positive normal cells include epithelial cells in skin adnexa, breast, and subsets of cerebellar neurons. KIT positivity has been variably reported in sarcomas such as angiosarcoma, Ewing sarcoma, synovial sarcoma, leiomyosarcoma, and MFH; results of the last three are controversial. The variations in published data may result from incomplete specificity of some polyclonal antibodies, possibly contributed by too high dilutions. Also, KIT is expressed in pulmonary and other small cell carcinomas, adenoid cystic carcinoma, renal chromophobe carcinoma, thymic, and some ovarian and few breast carcinomas. A good KIT antibody reacts with known KIT positive cells, and smooth muscle cells and fibroblasts are negative. KIT deficiency due to hereditary nonsense/missense mutations leads to disruption of KIT-dependent functions such as erythropoiesis, skin pigmentation, fertility, and gastrointestinal motility. Conversely, pathologic activation of KIT through gain-of-function mutations leads to neoplasia of KIT-dependent and KIT-positive cell types at least in three different systems: mast cells/myeloid cells--mastocytosis/acute myeloid leukemia, germ cells--seminoma, and Cajal cells--gastrointestinal stromal tumors (GISTs). KIT tyrosine kinase inhibitors such as imatinib mesylate are the generally accepted treatment of metastatic GISTs, and their availability has prompted an active search for other treatment targets among KIT-positive tumors such as myeloid leukemias and small cell carcinoma of the lung, with variable and often nonconvincing results.

Expression of CD117 (c-kit) receptor in dysgerminoma of the ovary: diagnostic and therapeutic implications

The proto-oncogene c-kit encodes a tyrosine kinase receptor, c-kit (CD117), which has been implicated in the development of a number of human malignancies. While the preferential expression of this protein has been well documented in testicular seminomas, there is little data concerning its expression in dysgerminomas of the ovary. We examined the expression of c-kit in 30 cases of ovarian dysgerminomas using immunohistohemical staining with a polyclonal anti-CD117 antibody. Staining was graded in a semiquantitative manner as follows: negative (no staining), 1+(1-10% staining), 2+(10-29% staining), 3+(30-50% staining), or 4+ (>50% staining). Of the 30 cases examined, 26 (87%) demonstrated immunoreactivity for CD117. In total, 10 (33%) demonstrated 4+ staining; 9 (30%) demonstrated 3+staining; 3 (10%) demonstrated 2+staining; 4 (13%) demonstrated 1+staining; and 4 (13%) demonstrated no staining. In conclusion, CD117 immunoreactivity was detected in 87% of ovarian dysgerminomas, a finding that correlates with previously reported frequencies of CD117 expression in seminomas (78-100%). Thus, antibodies to c-kit may be a useful diagnostic marker for ovarian dysgerminoma. Although the prognosis of patients with dysgerminoma is generally good, this receptor could potentially serve as a target for site-specific immunotherapy as an alternative and/or complement to conventional treatment options.

Detection of overexpressed and phosphorylated wild-type kit receptor in surgical specimens of small cell lung cancer

PURPOSE

The combinations of various chemotherapeutic drugs currently used to treat advanced small cell lung cancer (SCLC) led to similarly poor survival outcomes, which is why new molecular biology approaches are needed to design and select targeted therapies.

EXPERIMENTAL DESIGN

Thirteen stage I SCLC surgical specimens were screened for c-Kit gene mutations by sequencing whole cDNA and for KIT receptor expression/activation by immunoprecipitation and Western blotting. Both the paraffin-embedded and frozen materials were analyzed by immunocytochemistry, and the stem cell factor cognate ligand was assessed by retrotranscription PCR.

RESULTS

In all cases, we showed the presence of wild-type KIT receptors by analyzing the entire coding sequence, which together with the detection of the cognate ligand stem cell factor, supports the establishment of an autocrine loop. In addition, the KIT receptor was activated/phosphorylated. The immunoprecipitation/Western blotting data fit the observed immunophenotype. Interestingly, comparison of the level of KIT expression was at least 10 times higher in the tumoral specimens than the normal reference lungs.

CONCLUSIONS

The KIT molecular profile derived from the analysis of SCLC surgical specimens shows that wild-type KIT is overexpressed and phosphorylated in the presence of stem cell factor. This finding, which is consistent with pathological KIT activation driven by an autocrine loop, is particularly interesting in the light of the recent development of new tyrosine kinase inhibitory drugs, which are highly effective in blocking wild-type KIT receptors.

A phase II trial of imatinib (ST1571) in patients with c-kit expressing relapsed small-cell lung cancer: a CALGB and NCCTG study

BACKGROUND

The aim of the present study was to evaluate the clinical activity of imatinib mesylate in patients with recurrent and refractory c-kit-expressing small-cell lung cancer.

PATIENTS AND METHODS

Patients with c-kit-expressing SCLC (> or =1+ by immunohistochemistry) were enrolled in two groups. Arm A included patients with disease progression <3 months and arm B included patients with disease progression > or =3 months after previous treatment. Imatinib was administered at a dose of 400 mg b.i.d. continuously, with a cycle length of 28 days. A single stage Simon design with a planned interim analysis was used to evaluate the 16-week progression free rate in each arm.

RESULTS

A total of 29 evaluable patients were entered into the study (seven in arm A, median age 68; 22 in arm B, median age 64.5). Median number of treatment cycles was one in both arms. Grade 3+ non-hematologic adverse events were seen in 15 (52%) patients, with nausea, vomiting, dyspnea, fatigue, anorexia and dehydration each occurring in at least 10% of patients. Median survival was 3.9 and 5.3 months and median time to progression was 1 and 1.1 months for arms A and B, respectively. Enrollment to arm A was temporarily suspended prior to reaching interim analysis due to striking early disease progression (29%), early deaths (29%) and patient refusal (42%). No objective responses and no confirmed stable disease > or =6 weeks were seen in either arm. Accrual was permanently terminated to both arms as only one patient was progression-free at 16 weeks.

CONCLUSION

Imatinib failed to demonstrate any clinical activity in spite of patient selection for c-kit-expressing SCLC. Our results strengthen the collective evidence that prediction of efficacy of novel therapeutic agents based on target expression, rather than pathway activation (for example, through activating mutations), may not be a valid paradigm for drug development.

Imatinib mesylate lacks activity in small cell lung carcinoma expressing c-kit protein: a phase II clinical trial

BACKGROUND

Imatinib inhibits the c-kit tyrosine kinase, which, accounts for its activity in gastrointestinal stromal tumors. The presence of c-kit protein expression in small cell lung carcinoma (SCLC) tumor specimens, as well as in vitro data supporting the role of c-kit in autocrine and paracrine growth stimulation specifically in SCLC, provided a rationale for studying imatinib in this disease. The authors conducted a Phase II single-institution study of imatinib in patients with recurrent SCLC whose tumor specimens expressed c-kit protein.

METHODS

Patients with progressive SCLC after one or two previous chemotherapy regimens consented to have their tumor specimens screened by immunoperoxidase stain (CD117, Dako Corporation, Carpinteria, CA) for c-kit protein expression. If present, individuals were then eligible for treatment with an imatinib dose of 400 mg orally twice daily (total, 800 mg per day).

RESULTS

The presence of c-kit protein was assessable in 36 of 39 (92%) tumor samples. Twenty-eight (78%) tumor samples had immunohistochemical staining for c-kit protein. Twelve patients were enrolled in the treatment portion of the current study. No responses were observed, and all patients had disease progression by Week 4. Edema, fatigue, nausea, and electrolyte abnormalities were the primary toxicities.

CONCLUSIONS

Imatinib did not have antitumor activity against SCLC, even with c-kit protein present in tumor specimens. The dismal prognosis for these patients with progressive SCLC emphasized the urgent need for continued studies of new therapies in this population.

PKC theta, a novel immunohistochemical marker for gastrointestinal stromal tumors (GIST), especially useful for identifying KIT-negative tumors

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor in the digestive tract and the majority of GIST has characteristic gain-of-function mutations of the c-kit gene, which encodes the KIT receptor for stem cell factor. The present study aimed to establish the usefulness of protein kinase C theta (PKC theta) as an immunohistochemical marker for GIST in comparison with KIT immunohistochemistry. PKC theta immunohistochemistry was carried out not only on 48 cases of GIST and another 40 cases of gastrointestinal mesenchymal tumors, but also on 24 cases of various tumors known to be immunohistochemically positive for KIT. Immunohistochemically, 41 out of 48 cases (85%) of GIST were positive for PKC theta, and its expression was confirmed by Western blot analysis using six cases of surgically resected GIST. In the present study there were six GIST immunohistochemically negative for KIT, which histologically revealed a myxoid epithelioid appearance characteristic to that of GIST with platelet-derived growth factor receptor alpha mutation. All six GIST were immunohistochemically positive for PKC theta. No PKC theta immunoreactivity was observed in other gastrointestinal mesenchymal tumors and various KIT-positive tumors except for three cases (14%) of gastrointestinal schwannomas. The present study revealed that PKC theta is an immunohistochemically novel and useful marker for GIST, especially for GIST negative for KIT.

Cytokeratin 20 confirms merkel cell metastasis to stomach

Merkel cell carcinoma (MCC) is an uncommon, aggressive neuroendocrine carcinoma of the skin. Its prognosis is poor because of involvement of regional lymph nodes and metastases to distant sites such as bone, liver, lung, and brain. Very few metastases are reported to the gastrointestinal tract. Several studies have shown the utility of cytokeratin 20 to differentiate MCC from other small round blue cell tumors, particularly those with neuroendocrine differentiation. In this case report, we present an unusual metastasis to the stomach and the utility of cytokeratin 20 immunohistochemistry to confirm MCC.

c-kit Expression in small cell carcinoma of the urinary bladder: prognostic and therapeutic implications

The prognosis for small cell carcinoma of the urinary bladder is poor, and strategies for improved therapy are needed. Targeted therapy against the c-kit proto-oncogene has been successful in the management of gastrointestinal stromal tumor. We investigated the expression of c-kit in 52 cases of small cell carcinoma of the urinary bladder. Specimens with more than 10% of cells demonstrating strong membrane staining were considered to have positive immunostaining for c-kit. c-kit expression was detected in 21 of 52 specimens from these patients. Among the 21 specimens, seven had less than 10% staining, and were considered to be negative. Nine had 11-50% staining, and five had more than 50% staining. Overall, 14 of 52 (27%) small cell carcinomas of the urinary bladder were positive for c-kit expression. During a median follow-up of 11 months, 60% of the patients died of bladder cancer. No association was found between c-kit expression and survival or other clinicopathologic parameters. Five-year cancer-specific survivals for c-kit-positive and c-kit-negative tumors were 9 and 15%, respectively (P=0.36). A significant proportion (27%) of small cell carcinomas of the urinary bladder expressed c-kit, suggesting that it may prove useful as a therapeutic target in small cell carcinoma of the urinary bladder.

In vivo efficacy of STI571 in xenografted human small cell lung cancer alone or combined with chemotherapy

STI571, or imatinib, selectively inhibits BCR/ABL, PDGFR and c-kit kinase activity. It has been reported that a large proportion of small cell lung cancer (SCLC) cell lines and tumors express c-kit and that STI571 inhibits tumor cell growth. We therefore investigated the therapeutic efficacy of STI571, alone or combined with chemotherapy, in human SCLC cells or tumors xenografted into nude mice. The level of c-kit mRNA expression was variable in SCLC tumors (positive for 2 of 4 xenografts), and c-kit protein was not detected by immunohistochemistry. On the 4 xenografted tumors, PDGFRalpha and PDGFRbeta were not detected by immunohistochemistry. STI571 induced inhibition of proliferation of the SCLC6 cell line without inducing apoptosis; in contrast, in combination with etoposide or topotecan, the growth inhibition of SCLC6 cells induced by STI571 was increased, with apoptotic DNA fragmentation. Four human SCLC xenografts (SCLC6, SCLC61, SCLC74 and SCLC108) were transplanted into mice. After intraperitoneal injection of STI571, we observed 80%, 40% and 78% growth inhibition of SCLC6, SCLC61 and SCLC108 tumors, respectively, without any significant inhibition of SCLC74 tumor growth. In mice bearing responsive SCLC tumors, we observed an increase of growth inhibition induced by chemotherapy (etoposide + ifosfamide or topotecan) by concomitant and continuous administration of STI571, associated with an increase of toxic deaths. In SCLC6-bearing mice receiving sequential treatments, we observed a reduction of toxic deaths but a decrease of synergistic antitumor efficacy. In conclusion, the efficacy of STI571 alone in SCLC xenografted tumors was variable and did not depend on c-kit expression. Moreover, a significant increase of chemotherapy-induced growth inhibition was obtained by concomitant administration of STI571 that should be carefully investigated in SCLC patients.

The role of new targeted therapies in small-cell lung cancer

Lung cancer is the leading world-wide cause of cancer death. Small-cell lung cancer (SCLC) accounts for 20-25% of lung carcinomas. Chemotherapy is the cornerstone of treatment of SCLC. In limited disease, median survival is about 12-16 months with 4-5% of long-term survivors, in extensive disease median survival is 7-11 months. Improving the survival rate of patients with SCLC requires a better understanding of tumour biology and the subsequent development of novel therapeutic strategies. Several targeted agents have been introduced into clinical trials in SCLC and some phase III studies have already produced definitive results. Currently, the minority of these new agents offers a promise of improved outcomes, and negative results are more commonly reported than positive ones. To date, no targeted therapy has been approved for use in the treatment of patients with SCLC. This review will focus on the main novel biologic agents investigated in the treatment of SCLC.

Expression and mutational status of c-kit in small-cell lung cancer: prognostic relevance

PURPOSE

The c-kit protein, also known as CD117, is a member of the type III receptor tyrosine kinase family. Kinase activity has been implicated in the pathophysiology of many tumors, including small-cell lung carcinoma (SCLC). Autocrine or paracrine activation of c-kit by its ligand has been postulated for lung cancer, but this receptor can also be activated by mutations of the c-kit gene. We examined c-kit expression and mutational status in SCLC to verify its putative expression and genetic alterations, as well as its eventual prognostic impact.

EXPERIMENTAL DESIGN

We studied 60 SCLC samples to determine the mutations of the coding region of the gene; the exons 9 and 11 were analyzed by PCR-single-strand conformational polymorphism and automated sequencing. Moreover, c-kit expression was evaluated in 55 samples by immunohistochemical method.

RESULTS

Expression of c-kit was demonstrated in about 40% of SCLC samples. Two mutations in exon 9 and three mutations in exon 11 were found. Kaplan-Meier analysis revealed no prognostic significance of c-kit expression for survival.

CONCLUSIONS

In our series, the expression of c-kit and its mutational status failed to appear relevant or to have a significant impact on survival; this makes the therapeutic approach with an inhibitor of tyrosine kinase more difficult in SCLC until a sure demonstration of c-kit implication is obtained for this tumor.

Prevalence of KIT expression in human tumors

PURPOSE

KIT is a target for imatinib mesylate (Gleevec; Novartis Pharma, Basel, Switzerland). Gastrointestinal stromal tumors (GISTs) express KIT and respond favorably to imatinib therapy. To determine other tumors in which such a molecular targeted therapy might be indicated, we investigated KIT expression in different human tumor types. Because recent studies in GISTs suggest that KIT-activating mutations predict response to imatinib therapy, we also sequenced a subset of positive tumors.

MATERIALS AND METHODS

More than 3,000 tumors from more than 120 different tumor categories were analyzed by immunohistochemistry in a tissue microarray format. Seven commercially available anti-KIT antibodies were initially evaluated. The antibody A4502 (DAKO) was selected for analysis because of a high frequency of positivity in GIST and low staining background in other tissues. To determine the frequency of KIT mutations in various tumor types, the exons 2, 8, 9, 11, 13, and 17 (where mutations previously were reported) were sequenced in 36 tumors with strong KIT expression.

RESULTS

KIT positivity was detected in 28 of 28 GISTs (100%), 42 of 50 seminomas (84%), 34 of 52 adenoid-cystic carcinomas (65%), 14 of 39 malignant melanomas (35%), and eight of 47 large-cell carcinomas of the lung (17%), as well as in 47 additional tumor types. KIT mutations were found in six of 12 analyzed GISTs, but only in one of 24 other tumors.

CONCLUSION

The results suggest that KIT expression occurs infrequently in most tumor types and that, with the exception of GISTs, KIT gene mutations are rare in immunohistochemically KIT-positive tumors.

KIT and platelet-derived growth factor receptor alpha tyrosine kinase gene mutations and KIT amplifications in human solid tumors

PURPOSE

Mutated KIT and platelet-derived growth factor receptor alpha (PDGFRalpha) tyrosine kinases are the principal targets for imatinib mesylate in the treatment of gastrointestinal stromal tumors (GISTs). The frequency of activating KIT and PDGFRA gene mutations in most other histologic types of human cancer is not known.

MATERIALS AND METHODS

KIT exons 9, 11, 13, and 17 and PDGFRA exons 11 and 17 of 334 human cancers were screened for mutations using sensitive denaturing high-performance liquid chromatography (DHPLC). In addition, all KIT exons from 9 to 21 of 115 tumors were screened. Thirty-two histologic tumor types were examined. Samples with abnormal findings in DHLPC were sequenced. Immunostaining for the KIT protein (CD117) was performed in 322 (96.4%) of the 334 cases.

RESULTS

Of the 3,039 exons screened, only 17 had mutation. All 17 cases with either mutated KIT (n = 15) or PDGFRA (n = 2) were histologically GIST tumors, whereas none of the other histologic types of cancer (n = 316) harbored KIT or PDGFRA mutation. KIT immunostaining was rarely positive except in GISTs (18 of 18), small-cell lung cancer (10 of 30; 33%), and testicular teratocarcinoma (four of 17; 24%). Wild-type KIT gene amplification or chromosome 4 aneuploidy was common (seven of 12) in non-GIST tumors with strong KIT protein expression when studied with fluorescence in situ hybridization.

CONCLUSION

Despite frequent KIT protein expression in some tumor types, KIT and PDGFRA gene mutations are uncommon in most human cancers. Cancer KIT expression is frequently associated with multiple copies of the wild-type KIT gene.

Expression of the proto-oncogene c-KIT in normal and tumor tissues from colorectal carcinoma patients

BACKGROUND AND AIMS

The proto-oncogene c-KIT encodes a tyrosine kinase receptor essential during embryonic development and postnatal life. Although deregulated expression of c-KIT has been reported, its role in colorectal carcinoma remains controversial: some authors have described a correlation between c-KIT expression and colorectal cancer (CRC), while others have failed to detect the receptor in the majority of neoplasia examined. To address this question, we designed a prospective study to analyze the expression of c-KIT in normal and neoplastic colonic mucosa of the same patient.

PATIENTS AND METHODS

We analyzed the tissues of 20 patients undergoing surgical resection for colorectal carcinoma by reverse transcriptase-polymerase chain reaction, Western blot and immunohistochemistry, whose results were correlated with histopathological parameters.

RESULTS

Most patients (90%) showed c-KIT expression in normal tissue both at RNA and protein level, while in neoplastic tissue it was observed in 30% of patients at RNA level and in 10% at protein level. By immunohistochemistry the localization of c-KIT protein in the normal colon was restricted to interstitial cells scattered in the stroma, whereas the non-neoplastic epithelium was always negative. The mucinous carcinomas were all c-KIT negative, whereas the only case in which c-KIT was displayed in the neoplastic epithelium was a G3 adenocarcinoma.

CONCLUSION

Most colorectal carcinomas do not express c-KIT. We suggest that c-KIT expression is rarely present in this neoplasia; thus, the use of receptor inhibitors should be conducted in selected sub-groups of colon carcinoma patients, subsequent to the clear demonstration of c-KIT overexpression in the neoplastic cells.

The spectrum of Kit (CD117) immunoreactivity in lung and pleural tumors: a study of 96 cases using a single-source antibody with a review of the literature

CONTEXT

The development of successful chemotherapeutic agents directed against the Kit receptor tyrosine kinase protein has generated intense interest in the Kit (CD117) immunoreactivity of various neoplasms. Immunoreactivity for Kit in small cell lung carcinoma (SCLC) has been well established. However, data on Kit immunostaining in other lung tumors is limited. Likewise, while solitary fibrous tumors of the gastrointestinal tract have been examined for Kit expression, the Kit staining characteristics of their counterpart in the pleura, namely, localized fibrous tumor, are not well known.

OBJECTIVE

To characterize the Kit immunohistochemical profiles of major types of lung and pleural tumors.

DESIGN

We stained 60 lung carcinomas, including 11 SCLCs, 4 large cell neuroendocrine carcinomas, 22 squamous cell carcinomas, 23 adenocarcinomas, 11 pulmonary carcinoid tumors, 19 pleural malignant mesotheliomas, and 6 localized pleural fibrous tumors with a commonly used polyclonal Kit antibody.

RESULTS

Small cell lung carcinomas demonstrated Kit staining in 82% of cases, nearly all of which demonstrated moderate to intense immunoreactivity. Immunostaining was observed in 25% of large cell neuroendocrine carcinomas. Focal staining was observed in 9% of squamous cell carcinomas and 17% of adenocarcinomas. None of the pulmonary carcinoid tumors were immunoreactive. Moderately intense immunostaining was present in 50% of localized fibrous tumors. Malignant mesotheliomas were nonimmunoreactive for Kit in 95% of cases.

CONCLUSION

Non-small cell lung carcinomas showed very limited expression of Kit. Lung tumors with neuroendocrine differentiation exhibited a wide spectrum of Kit immunoreactivity, ranging from rare in pulmonary carcinoid tumors to frequent in SCLC. The high frequency of Kit immunostaining in SCLC has important potential therapeutic implications. Demonstration of Kit positivity in some localized fibrous tumors in this study contrasts with absent immunoreactivity in solitary fibrous tumors of the gastrointestinal tract. The paucity of Kit staining in malignant mesothelioma suggests these tumors are unlikely to respond to currently available tyrosine kinase inhibitors.

Overexpression of c-kit protein is an infrequent event in small cell carcinomas of the uterine cervix

Primary small cell carcinomas of the uterine cervix are uncommon but highly aggressive malignancies. The recent observations that c-kit proto-oncogene, a tyrosine kinase, is overexpressed in small cell lung cancers and that advanced c-kit-expressing gastrointestinal stromal tumors were successfully treated with a selective tyrosine kinase inhibitor STI-571 (Gleevec, imatinib mesylate) prompted us to investigate c-kit protein expression in cervical small cell carcinomas. Using a polyclonal antibody against c-kit protein (CD117), our immunohistochemical studies demonstrated a cytoplasmic staining in six of 22 cases (27%) of cervical small cell carcinoma. However, in five of these c-kit-positive cases, the immunoreactivity was focal and/or weak. Only one case (5%) exhibited a strong and diffuse staining pattern comparable to that seen in gastrointestinal stromal tumors. This was in contrast to small cell lung cancers where a positive staining for c-kit was observed in nine of 14 cases (64%) included in the study for comparison. Among them, five (36%) exhibited a strong and diffuse staining pattern. These results indicate that overexpression of c-kit protein is an infrequent event in small cell carcinomas of the uterine cervix. In comparison with small cell lung cancers, the findings presented in this report may reflect the difference in etiopathogenetic mechanisms underlying these two types of small cell carcinomas.