Richard C. Karl

Activating SRC mutation in a subset of advanced human colon cancers.

The discovery of Rous sarcoma virus (RSV) led to the identification of cellular Src (c–Src), a non-receptor tyrosine kinase, which has since been implicated in the development of numerous human cancers. c-Src has been found to be highly activated in colon cancers, particularly in those metastatic to the liver. Studies of the mechanism of c-Src regulation have suggested that c-Src kinase activity is downregulated by phosphorylation of a critical carboxy-terminal tyrosine (Tyr 530 in human c-Src, equivalent to Tyr 527 in chicken Src) and have implied the existence of activating mutations in this C-terminal regulatory region. We report here the identification of a truncating mutation in SRC at codon 531 in 12% of cases of advanced human colon cancer tested and demonstrate that the mutation is activating, transforming, tumorigenic and promotes metastasis. These results provide, for the first time, genetic evidence that activating SRC mutations may have a role in the malignant progression of human colon cancer.

Factors Affecting Morbidity, Mortality, and Survival in Patients Undergoing Ivor Lewis Esophagogastrectomy

OBJECTIVES To examine the safety of transthoracic esophagogastrectomy (TTE) in a multidisciplinary cancer center and to determine which clinical parameters influenced survival and the rates of death and complications. SUMMARY BACKGROUND DATA Although the incidence of cancer at the gastroesophageal junction has been rising rapidly in the United States, controversy still exists about the safety of surgical procedures designed to remove the distal esophagus and proximal stomach. Alternatives to TTE have been proposed because of the reportedly high rates of death and complications associated with the procedure. METHODS Data from 143 patients treated by TTE by one author (1989-1999) were entered into a computerized database. Preoperative clinical parameters were tested for effect on death, complications, and survival. RESULTS The patient population consisted of 127 men and 16 women. One hundred twenty-one patients had a history of tobacco abuse, and 118 reported the regular ingestion of alcohol. One hundred fifteen patients had adenocarcinoma, 16 had squamous cell cancer, 6 had another form of esophageal tumor, and 6 had high-grade dysplasia associated with Barrett epithelia. Fifty-six patients had adenocarcinomas arising in Barrett epithelium. Twenty-eight patients were treated with neoadjuvant chemoradiation before surgery. Three patients died within 30 days of surgery (mortality rate 2.1%). Five patients (3.5%) had a documented anastomotic leak; three died). Overall, 42 patients had complications (29%). Twenty-six had pulmonary complications (19%). The mean length of stay in the intensive care unit was 3.35 days; the mean hospital length of stay was 13.54 days. The overall 3-year survival rate was 29.6%. CONCLUSIONS A high ASA score and the development of complications predicted an increased length of stay. The presence of diabetes predicted the development of complication and an increased length of stay. None of the other parameters tested predicted perioperative death or complications. Only disease stage, diabetes, and blood transfusion affected overall survival. From these results with a large series of patients with gastroesophageal junction cancers, TTE can be performed with a low death rate (2.1%), a low leak rate (3. 5%), and an acceptable complication rate (29%).

Local Excision of T2 and T3 Rectal Cancers After Downstaging Chemoradiation

ObjectiveTo evaluate the safety and efficacy of local excision in patients with T2 and T3 distal rectal cancers that have been downstaged by preoperative chemoradiation. Summary Background DataT2 and T3 cancers treated by local excision alone are associated with unacceptably high recurrence rates. The authors hypothesized that preoperative chemoradiation might downstage both T2 and T3 lesions and significantly expand the indications for local excision. MethodsLocal excision was performed after preoperative chemoradiation on patients with a complete clinical response or on patients who were either ineligible for or refused to undergo abdominoperineal resection. Local excision was approached transanally by removing full-thickness rectal wall and the underlying mesorectum. ResultsFrom 1994 to 2000, 95 patients with rectal cancers underwent preoperative chemoradiation and surgical resection for curative intent. Of these, 26 patients (28%), 19 men and 7 women, with a mean age of 63 years (range 44–90), underwent local excision. Pretreatment endoscopic ultrasound classifications included 5 T2N0, 13 T3N0, 7 T3N1, and 1 not done. Pathologic partial and complete responses were achieved in 9 of 26 (35%) and 17 of 26 (65%) patients, respectively. Two of nine partial responders underwent immediate abdominoperineal resection. The mean follow-up was 24 months (median 19, range 6–77). The only recurrence was in a patient who refused to undergo abdominoperineal resection after a partial response. There was one postoperative death from a stroke. This treatment was associated with a low rate of complications. ConclusionLocal excision appears to be an effective alternative treatment to radical surgical resection for a highly select subset of patients with T2 and T3 adenocarcinomas of the distal rectum who show a complete pathologic response to preoperative chemoradiation.

Expression of insulin-like growth factor-1 receptor in human colorectal cancer

The activation of the insulinlike growth factor 1/IGF-1 receptor system (IGF1/IGF1-R) has recently emerged as critical event in transformation and tumorigenicity of several murine and human tumors. Expression of IGF1 and of IGF1-R has been demonstrated in normal and neoplastic intestinal cell lines of rats and humans. However, the modulation of IGF1-R expression during the progression from normal colonic mucosa to adenoma, to carcinoma, and to metastasis, has not been evaluated. In this retrospective study, we investigated the expression of IGF1-R in 12 colonic adenomas (AD), 36 primary colorectal adenocarcinomas (CA), and in 27 corresponding metastases (MT). Normal colonic mucosa (N) was adjacent to the CA in 34 cases. Formalin-fixed, paraffin-embedded tissues of each case were immunostained using the avidin-biotin-peroxidase method. We used an anti-IGF1-R rabbit polyclonal antibody (Santa Cruz Biotechnology, CA; dilution 1:100). Positive staining was quantitated by CAS-200. Moderate to strong cytoplasmic immunostaining was observed in 34 of 36 CA (96%), and in 25 of 27 MT (93%). In all of the positive MTs, the intensity of the staining was always strong. In 10 of 12 ADs (83%), only a faint cytoplasmic stain was identified. Normal mucosa when present was negative. Strong IGF1-R positivity correlated with higher grade and higher-stage tumors (P < .01). These data suggest a role of IGF1-R expression during the progression of colorectal adenoma to carcinoma. An increased number of IGF1-R receptors may favor the metastasis of colorectal cancer.

Coexpression of IGF-1R and c-Src proteins in human pancreatic ductal adenocarcinoma

Aberrant c-Src protein kinase activation has been identified as one of the molecular alterations involved in human pancreatic carcinogenesis. It has been postulated that c-Src may induce transformation by causing the overexpression of the insulinlike growth factor-1 receptor (IGF-1R) in pancreatic tumor cell lines. To further study the interaction between c-Src and IGF-1R proteins in human pancreatic cancer, we examined their coexpression in 47 human pancreatic ductal adenocarcinomas (PDA). Formalin-fixed, paraffin-embedded sections from 47 cases of PDA were stained using the immunohistochemical avidin–biotin–peroxidase method. We used an anti-human IGF-1R mouse monoclonal antibody (dilution 1:100 with antigen retrieval), and an anti-c-Src mouse monoclonal antibody (dilution 1:100 with antigen retrieval). The stains were semiquantitatively evaluated using the Allred score system, assessing intensity of stain and percentage of positive tumor cells. High cytoplasmic c-Src expression (Allred score 7–8) was seen in 33/47 (70%) tumors. In only 4 cases was c-Src either negative or low (Allred score 3). Strong and diffuse membranous IGF-1R stain (Allred score 7–8) was identified in 30/47 (64%) tumors. IGF-1R staining was low (Alled score 2–4) in 2 cases and negative in 1. Interestingly, in 40/47 (85%) cases c-Src and IGF-1R stains had similar scores. An inverse staining pattern was detected in only 6/47 (13%) tumors. Normal pancreatic ducts as well as areas of chronic pancreatitis were negative for IGF-1R. In conclusion, our data support the role of IGF-1R and c-Src in human pancreatic carcinogenesis; the coexpression of both these molecules may play an important role in transformation of pancreatic ductal cells.

CD44V6 expression in human colorectal carcinoma

CD44 is an adhesion molecule involved in cell-to-cell and cell-to-matrix interactions. This transmembrane glycoprotein exists in either standard or variant forms, originated by alternative splicing. One of the isoforms (CD44V6) has been shown, in some systems, to modify the metastatic potential of tumor cells. To investigate the role of this biomarker as possible prognostic antigen in colorectal cancer, we immunohistochemically analyzed the distribution of CD44V6 expression on formalin-fixed, paraffin-embedded tissues from resected colorectal cancers of 34 patients. The monoclonal antibody VFF7 against the amino acid sequence encoded by exon CD44V6 was applied using the avidin-biotin-peroxidase method. For each resected specimen, normal (N), adenomatous (AD), and carcinomatous (CA) colonic mucosa were tested. In 68% of the resected cases, these areas were present in the same slide, and in 76% of cases, nodal or liver metastases (MT) were available for evaluation. Adenomatous polyp biopsy specimens of 10 carcinoma-free patients were also tested. In selected cases, CD44V6 expression was also determined using the Western blot immunoprecipitation technique. CD44V6 immunoreactivity was detected in 100% of the ADs, and in 91% of CAs, but was mostly weak in only 38% of MTs (n=26). In 49% (n=35) of ADs, 11% (n=34) of CAs, and 4% of MTs (n=26), the stain was moderate to strong. CD44V6 immunoreactivity was predominantly membranous in ADs and cytoplasmic in MTs. In the CAs, both staining patterns were noted. Interestingly, the normal mucosa had a weak subnuclear localization of the stain. In the cases evaluated by Western blotting immunoprecipitation analysis, the level of CD44V6 protein expression was similar to that obtained by immunohistochemistry. No correlation was found with tumor type, stage, or patient survival. The predominant CD44V6 expression in ADs and CAs, but not in MTs, suggests that, in many cases, the expression of this adhesion molecule may be lost during the acquisition of migratory function by the tumor cells.

Modification of insulin-like growth factor 1 receptor, c-Src, and Bcl-XL protein expression during the progression of barrett’s neoplasia

Oncogenes, growth factors, cell surface receptors, and cell-cycle and apoptotic regulatory proteins have been implicated in the growth regulation and progression of Barretts-associated neoplasia. Among these, insulin-like growth factor 1 receptor (IGF1-R) and c-Src are reported to be key regulators of mitogenesis and tumorigenesis. In addition, c-Src may exert its transforming capability by inducing increased expression of IGF1-R on the neoplastic cells. Bcl-X(L), a member of the Bcl-2 family, blocks apoptosis and has been reported to increase in Barretts-associated neoplasia. To study the modifications in IGF1-R, c-Src, and Bcl-X(L) protein expression during the progression of Barretts-associated neoplasia, we analyzed 34 resected gastroesophagectomy specimens by immunohistochemistry using antibodies to human IGF1-R, c-Src, and Bcl-X(L). In these cases, we found 22 intestinal (Barretts) metaplasias (IMs), 25 low-grade dysplasias (LGDs), 28 high-grade dysplasias (HGDs), 34 invasive adenocarcinomas (CAs), and 19 lymph node metastases. High IGF1-R cytoplasmic staining was present in 14 of 19 (74%) node metastases, in 28 of 34 (82%) CAs, in 18 of 28 (64%) HGDs, in 13 of 25 (52%) LGDs, and in 5 of 22 (23%) IMs. Strong and diffuse c-Src expression was identified in 17 of 19 (89%) node metastases, in 29 of 34 (85%) Cas, in 26 of 28 (93%) HGDs, in 18 of 25 (72%) LGDs, and in 9 of 22 (41%) IMs. Bcl-X(L) cytoplasmic staining was evident in 12 of 19 (63%) node metastases, in 20 of 34 (59%) Cas, in 20 of 28 (71%) HGDs, in 15 of 25 (60%) LGDs, and in 6 of 22 (27%) IMs. In 11 cases, c-Src activity was measured by kinase assay and reflected the immunohistochemical results. Our data indicate that expression levels of IGF1-R, c-Src, and Bcl-X(L) proteins are coordinately elevated in Barretts-associated neoplasia. These findings indicate important roles of these growth regulatory proteins in the malignant progression of Barretts-associated neoplasia.

Antiproliferative and Proapoptotic Effect of Ascorbyl Stearate in Human Pancreatic Cancer Cells: Association with Decreased Expression of Insulin-Like Growth Factor 1 Receptor

Pancreatic cancer is an aggressive tumor with short median survival and high mortality rate. Alternative therapeutic modalities are currently being evaluated for pancreatic cancer. Here we studied the effects of ascorbyl stearate (Asc-S), a nontoxic, lipophilic derivative of ascorbic acid, on pancreatic cancer. Treatment of human pancreatic carcinoma cells with Asc-S (50–200 μM) resulted in a dose-dependent inhibition of their proliferation. Asc-S slowed down the cell cycle, accumulating, PANC-1 cells in late G2-M phase. Furthermore, Asc-S treatment (150 μM) markedly inhibited growth in soft agar and facilitated apoptosis of PANC-1 cells but not of Capan-2 cells. These effects were accompanied by a significant reduction in insulin-like growth factor 1 receptor (IGF1-R) expression, as compared to untreated controls. Interestingly, Capan-2 cells, the least responsive to Asc-S treatment, did not overexpress the IGF1-R. The results demonstrate the efficacy of Asc-S in inhibing growth of pancreatic cancer cells and warrant additional studies to explore the potential utility of this compound as an alternative and/or adjuvant therapeutic modality for pancreatic cancer.

Neoadjuvant chemoradiotherapy is not associated with a higher complication rate vs. surgery alone in patients undergoing esophagectomy.

Recent studies have claimed a higher rate of perioperative complications related to the use of neoadjuvant chemoradiotherapy in the treatment of esophageal cancer. We tested the hypothesis that neoadjuvant chemoradiotherapy has no significant effect on the perioperative complication rate. Data on 155 patients with esophageal carcinoma treated between 1996 and 2001 were collected in a prospective database. This included 61 patients (40%) treated with neoadjuvant chemoradiotherapy (group I) and 94 patients (60%) who underwent esophagectomy alone (group II). Neoadjuvant therapy consisted of two courses of cisplatinum and continuous-infusion 5-fluorouracil with radiation followed by esophagectomy. Ivor-Lewis esophagectomy was performed in 146 (94%) and a transhiatal resection in nine (6%). The two groups (I vs. II) were comparable in terms of age (61.3±11 years vs. 64.8 ±11 years), diagnosis (adenocarcinoma: 82% vs. 83%; squamous cell carcinoma:11% vs. 16%), and stage (stage 0 to I: 39% vs. 38%; stage II: 25% vs. 34%; stage III: 30% vs. 24%; and stage IV: 6% vs. 4%). The neoadjuvant group had 23 complete responses, 11 partial responses, and 27 nonresponses. There were 39 complications (25.1%) for the cohort, which included three deaths (1.9%) and four anastomotic leaks (2.6%) demonstrated by Gastrografin swallow (1 in group I vs. 3 in group II. Only one leak required reoperation (group II); all others responded to conservative treatment. Group I had 14 complications (22.9%) vs. 25 (26.5%) in group II (P = NS). Groups were comparable with respect to the rate of pulmonary events (4.9% vs. 6.3 %), arrhythmias (6.5% vs. 8.5%), and stricture formation (6.5% vs. 7.4%). Neoadjuvant chemoradiotherapy in patients with esophageal cancer was not associated with increased perioperative morbidity or mortality. Complete response to chemoradiotherapy also did not affect the complication rate (26% vs. 22%).

Significance of Fas and retinoblastoma protein expression during the progression of Barrett's metaplasia to adenocarcinoma.

Background: Barrett’s esophagus (BE) is a premalignant lesion characterized by replacement of normal squamous epithelium with columnar epithelium. This lesion can progress to dysplasia and adenocarcinoma. Recently, the Fas receptor and retinoblastoma (Rb) protein have been described as important mediators of apoptosis and tumor suppression, respectively. This study was undertaken to examine their expression during the progression of metaplasia to adenocarcinoma in BE.Methods: In a review of 56 adenocarcinomas arising in BE, the specimen blocks were examined using the immunohistochemical avidin-biotin-peroxidase complex technique. For each specimen, areas of normal epithelium were compared with areas of metaplasia, dysplasia, or carcinoma (when present). Monoclonal mouse anti-human antibodies were used to identify Rb protein (Rb-Ab5, 1/50 dilution; Oncogene Science) and the 40–50-kDa cell membrane Fas protein (APO-1/Fas, 1/5 dilution; DAKO Corp.).Results: Loss of Rb staining was observed as the metaplasia progressed to dysplasia and carcinoma, indicating accumulation of unstainable aberrant protein. Conversely, Fas protein staining was undetectable or weak in normal or metaplastic epithelium, increasing in the areas of high-grade dysplasia and carcinoma. These differences were statistically significant (P < .001).Conclusions: The accumulation of abnormal Rb protein during the progression of Barrett’s metaplasia to carcinoma leads to unsuppressed tumor growth. Fas overexpression may represent a cellular attempt to balance the uncontrolled tumor proliferation by promoting apoptosis.