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.

Antibody-dependent cell-mediated cytotoxicity: detection by automated flow cytometry with ultramicro techniques.

Antibody-dependent cell-mediated cytotoxicity can be measured with as few as 1000 leukocytes with an automated flow cytometry technique.

Genetic risk of breast cancer.

Several cutting-edge strategies are being used to evaluate candidate genetic risk factors for breast cancer. These include linkage analysis for mapping out BRCA1 and BRCA2, mutational screening of candidate risk genes like CHEK2, ATM, BRIP1 and PALB2, which are associated with an intermediate level of breast cancer risk. Genome-wide association studies have revealed several low-penetrance breast cancer risk alleles. The predisposition factors are associated with different levels of breast cancer risk. Relative to control population, the risk in patients harboring high-risk BRCA1 and 2 mutations is over 10-fold, with intermediate penetrance genes 2 to 4-fold and with low penetrance alleles less than 1.5-fold. Overall, these factors account for about 25% of the genetic risk for breast cancer. In the remainder, genetic factors to contribute to the risk of breast cancer remain unknown and are a subject of current investigation. With discovery and validation of newer and clinically relevant predisposition factors, additional breast cancer risk categories may be recognized. BRCA1 and BRCA2 mutation testing allows identification of individuals at increased risk of breast cancer who are offered risk-reducing interventions. Targeted therapies are being developed that may refine management of patients with BRCA1 and BRCA2 mutations. Further genome-wide studies are required to identify clinically relevant molecular factors that will allow more accurate and widely applicable genetic risk stratification. Current efforts in discovery, validation and qualification of molecular markers of breast cancer risk offer considerable promise in the future to develop more accurate breast cancer risk assessment along with development of more effective chemopreventive and therapeutic strategies.

Identification of tumor markers in models of human colorectal cancer using a 19,200-element complementary DNA microarray.

Metastasis represents a crucial transition in disease development and progression and has a profound impact on survival for a wide variety of cancers. Cell line models of metastasis have played an important role in developing our understanding of the metastatic process. We used a 19,200-element human cDNA microarray to profile transcription in three paired cell-line models of colorectal tumor metastasis. By correlating expression patterns across these cell lines, we have identified 176 genes that appear to be differentially expressed (greater than 2-fold) in all highly metastatic cell lines relative to their reference. An analysis of these genes reiterates much of our understanding of the metastatic process and suggests additional genes, many of previously uncharacterized function, that may be causatively involved in, or at least prognostic of, metastasis. Northern analysis of a limited number of these genes validates the observed pattern of expression and suggests that further investigation and functional characterization of the identified genes is warranted.

Role of Src expression and activation in human cancer.

Since the original identification of a transmissible agent responsible for the development of tumors in chickens, now known to be a retrovirus encoding the v-src gene, significant progress has been made in defining the potential functions of its human homolog, SRC. The product of the human SRC gene, c-Src, is found to be over-expressed and highly activated in a wide variety of human cancers. The relationship between Src activation and cancer progression appears to be significant. Moreover, Src may have an influence on the development of the metastatic phenotype. This review discusses the data supporting a role for c-Src as a critical component of the signal transduction pathways that control cancer cell development and growth, and provides the rationale for targeting Src in drug discovery efforts.

Activation of c-Src by receptor tyrosine kinases in human colon cancer cells with high metastatic potential.

Recent data suggest that signal transduction may have a critical role in the development and regulation of the metastatic phenotype. Here, we investigated the role of c-Src activation in the process of human colon cancer metastasis to the liver. Our data, derived from two different sets of human colon cancer cell line metastatic variants, suggest that not only do highly-metastatic cells display constitutively elevated c-Src protein kinase activity when compared to poorly metastatic cells, but also that receptor tyrosine kinases participate in the ligand-activation of c-Src above basal levels. Specifically, the epidermal growth factor receptor (EGFR), p185HER2/Neu and the hepatocyte growth factor receptor (c-Met) appear to be linked to the process because they preferentially activate c-Src in highly-metastatic cells. EGFR was found to associate with c-Src in colon cancer cells and specific inhibitors of the EGFR resulted in a reduction of c-Src activity to basal levels. In addition, c-Src transfectants displayed partially-activated EGFRs, suggesting a feedback role for c-Src in the regulation of the EGFR. p185HER2/Neu was also identified in immunocomplexes of c-Src following ligand activation of the EGFR, but only in highly-metastatic cells. Collectively, these observations suggest a paradigm whereby c-Src interacts with multiple cell-surface growth factors in a catalytic fashion for the development of tumor cells with metastatic potential.

Analysis of colorectal cancer by comparative genomic hybridization: evidence for induction of the metastatic phenotype by loss of tumor suppressor genes.

Current models suggest that colon cancer initiation and progression are secondary to both the activation of oncogenes and the deletion of tumor suppressor genes. The role of each, however, is still poorly understood, particularly with regard to the induction of metastasis. We hypothesized that genetic differences exist between tumors that metastasize distantly and those that do not, and that oncogenes and tumor suppressor genes participate equally in this process. To address this hypothesis, human tumor specimens from localized [tumor-node-metastasis (TNM) stage I-III] and primary colon cancers (n = 10) were directly compared with metastatic (TNM stage IV) lesions (n = 10) using comparative genomic hybridization analysis. Although several alterations were shared equally between primary tumors and metastases (+7q, +19q, and +20q), two patterns of distinguishing alterations were observed: (a) alterations that were more extensive in liver metastases than in primary tumors (+8q, +13q, -4p, -8p, -15q, -17p, -18q, -21q, and -22q); and (b) alterations that were unique to metastatic lesions (-9q, -11q, and -17q). Overall, genetic losses were more common than gains, and, more importantly, the number of losses/tumor was significantly higher for metastases than for primary tumors (9.3 + 1.3 versus 4.1 + 0.7; P = 0.00062, Wilcoxon's rank-sum test). The distinct predominance of genetic losses in the metastatic lesions when compared with the primary localized tumors provides evidence that the metastatic phenotype is induced by the deletion of tumor suppressor genes and permits the construction of physical maps targeting regions where novel tumor suppressor genes are likely to exist.

Osteopontin regulates multiple functions contributing to human colon cancer development and progression.

Osteopontin (OPN) is a secreted phosphoglycoprotein known to interact with a number of integrin receptors. While increased OPN expression has been reported in a number of human cancers, and its cognate receptors (alphav-beta3, alphav-beta5, and alphav-beta1 integrins and CD44) have been identified, its role in colon cancer development and progression has not been extensively studied. We previously identified, using a combination of gene expression and tissue microarrays, that increased OPN expression is concordant with tumor stage. The current study examined the functional role of OPN in colon cancer progression and metastatic potential. The principal findings of this study were that both endogenous OPN expression (via stable transfection) as well as exogenous OPN (added to culture medium) enhanced the motility and invasive capacity of human colon cancer cells in vitro. OPN appeared to regulate motility though interaction with CD44. OPN expression also reduced intercellular (homotypic) adhesion, an important characteristic of metastatic cancer cells. Stable transfection of four poorly tumorigenic human colon cancer cell lines with OPN also resulted in enhanced tumorigenicity in vivo with increased proliferation and increased CD31 positive microvessel counts, concordant with the degree of OPN expression. Collectively, these results suggest that OPN may affect multiple functional components contributing to human colon cancer progression and solidifies its role in this process.

Identification of genetic alterations associated with the process of human experimental colon cancer liver metastasis in the nude mouse.

Understanding the genetic elements controlling the process of tumor metastasis to distant organ sites such as the liver may be the key to improving survivorship from colon cancer. By using standard cytogenetic techniques in combination with comparative genomic hybridization, multiple genetic imbalances within three human colon cancer cell lines previously selected for differences in liver-metastatic behavior were identified. The entire genome of one poorly metastatic cell line (KM12C) was compared directly with that of two highly metastatic cell lines (KM12SM, KM12L4A) derived from it. A number of chromosomal gains (8q, 12q15, 20q11.2) and losses (5p13, 6p21.3, 18) were common to all three cell lines and are likely related to early tumor development rather than to the selection process used to generate cell lines of increased metastatic potential. Chromosomal imbalances detected only in the highly metastatic cell lines were also observed. KM12SM showed losses of portions of 2p22, 2q24.3--> 2q32.2, 4p15.3--> cen, 4q24 without the 13q and 15q22.3 gains noted for KM12C. Both gains (1p31.3--> 1p21, 2q22--> 2q33, 3cen--> 3q26.2, 5q14--> 5q23, 6cen--> 6q23) and losses (16p, 17p, 17q 19p, 19q 22q) were observed for KM12L4A but not for the other two cell lines. Identification of these alterations provides valuable insight into the process of experimental liver metastasis and is a first step towards mapping genes linked to the terminal phases of human colon cancer progression.

Expression of annexins on the surfaces of non-metastatic and metastatic human and rodent tumor cells.

Annexins are a large group of calcium-dependent cytoskeletal- and membrane-associated proteins whose properties include cytoskeleton and phospholipid binding and mitotic signal transduction. Although annexin-like molecules have been reported on the external plasma membranes of certain cells, in general they are considered to be cytoplasmic proteins. We report here the heterogenous expression of certain annexins (I-VI) on the external cell surfaces of non-metastatic and metastatic murine (RAW117 large-cell lymphoma), rat (13762NF mammary adenocarcinoma) and some human (KM12 and HT29 colorectal carcinoma) cell lines but not on some other cell lines such as human (A375 and MeWo) and mouse (B16) melanoma. The implication of annexin cell surface expression in the metastatic process is discussed with respect to tumor cell adhesion.

ADCC analysis with the Coulter counter: a highly sensitive, ultramicro assay suitable for clinical and experimental application.

Antibody-dependent cellular cytotoxicity (ADCC) is an in vitro immune mechanism implicated in several in vivo phenomena such as transplant rejection, tumor immunity and parasite elimination. We developed a method for detecting ADCC using the Coulter Counter and the Coulter Channelyzer that circumvents many of the disadvantages associated with existing assays for ADCC. Effector mononuclear cells were incubated with chicken red blood cell (CRBC) targets and anti-target antibody for 1-1, 5h. Killing was quantified by the Coulter Counter on the basis of size differences between effector and target cell nuclei. Using a 4 microliter total volume we were able to detect cytotoxic levels of 55% when as few as 5000 effector cells were incubated with an equal number of target cells. This method for the detection of ADCC may be suitable for clinical and research application.

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.

Analysis of p53, p21WAF1, and TGF-beta1 in human ductal adenocarcinoma of the pancreas: TGF-beta1 protein expression predicts longer survival.

Loss of p53 and p21WAF1 expression have previously been reported in pancreatic adenocarcinoma. Despite these findings in several reports of oncogene and tumor suppressor gene alterations in pancreatic cancer, the clinical significance of these changes is still poorly understood. In an attempt to detect molecular prognostic markers for pancreatic carcinoma, we studied the immunohistochemical expression of p53, p21WAF1, and TGF-beta1 proteins in 42 pancreatic adenocarcinomas of the ductal type. The results were correlated with clinicopathologic findings to identify the markers with prognostic significance. p53 nuclear immunoreactivity was seen in 20 (48%) of the cases, and it was strong to moderate in 14 (33%) of them. p21WAF1 cytoplasmic positivity was found in 16 (38%) of the tumors, with 72% staining strong to moderate. TGF-beta1 stained the cytoplasm of the tumor cells in 13 (31%). Of the p53-negative cases, 12 (54%) exhibited p21WAF1 expression. In 3 (30%) of cases, TGF-beta1 reactivity was seen in the absence of p53 and p21WAF1 p53 positivity identified tumors of higher grade, but did not correlate with stage or survival. TGF-beta1 expression, however, identified low-grade tumors and patients with longer survival. No correlation was found between the expression of any of these molecular markers and smoking history. We report a significant correlation between TGF-beta1 reactivity and low-grade tumors and between TGF-beta1 and better survival. This is a novel finding pointing to TGF-beta1 as a possible new stage-independent predictor of tumor survival in pancreatic ductal adenocarcinoma. In agreement with others, we also found p53 mutation in 20 (48%) of the tumors.

Differential effect of human interferon on normal and neoplastic T- and B-cell lymphocytes.

The effect of human interferon (HIF) on the growth and function of normal and neoplastic proliferating human T and B cells was studied. Cell cycle analysis by flow-cytometry showed that up to 2000 units of HIF had little effect on the proliferating fraction (that is, the present S + G2 + M phases of the cell cycle) of normal T cells grown continuously wit growth-promoting factor from PHA-stimulated lymphocytes, while 500 units of HIF suppressed the percent S + G2 + M of the acute lymphocytic leukemia (ALL) T-cell line, MOLT, by 36%. Up to 2000 units of HIF had a moderate enhancing effect on the percent S + G2 + M of PWM-stimulated lymphocytes. In striking contrast, a single unit of HIF caused nearly 40% suppression of the percent S + G2 + M of Daudi, a Burkitt's lymphoma cell. One-thousand units of HIF did not decrease the number of antibody-forming normal cells, and up to 500 units of HIF did not inhibit the total Ig secreted by these cells. These results suggest that amounts of HIF affecting the proliferation of some neoplastic lymphoid cells has little effect on the proliferation of normal T and B cells. In addition, HIF does not appear to affect polyclonal induction of B-cell differentiation.

Depletion of dietary arginine inhibits growth of metastatic tumor.

The effects of dietary arginine on the growth of a murine colon tumor metastatic to the liver were examined in a model of advanced neoplastic disease. Tumor growth was influenced by arginine both in vivo and in vitro. An arginine-supplemented diet stimulated tumor growth by 55% compared with controls. Conversely, an arginine-depleted diet inhibited tumor growth by 78% compared with controls. In vitro culture of both murine and human colon tumor cells confirmed that arginine was necessary for cell growth. Flow-cytometric analysis using propidium iodide and bromodeoxyuridine suggested that colon tumor cells cultured without arginine enter a quiescent S phase and depend on arginine for further growth and cell cycle progression. The potential roles for selective dietary arginine modulation in patients with cancer with advanced disease are discussed.

Sentinel lymphadenectomy: a safe answer to less axillary surgery?

UNLABELLED: Lymphatic mapping techniques have the potential of changing the standard of surgical care of breast cancer patients. This paper reports a prospective study documenting the safety and efficacy of sentinel lymph node biopsy in 167 breast cancer patients and reviews the world literature on the procedure. METHODS: One hundred sixty-seven patients with newly diagnosed breast cancers underwent a prospective trial of intra-operative lymphatic mapping using a combination of vital blue dye and filtered technetium-labeled sulfur colloid. A sentinel lymph node (SLN) was defined as a blue node and/or "hot" node with a 10/1 ex-vivo gamma-probe ratio of SLN to non-SLN. All SLN were bi-valved, step-sectioned, and examined with routine H&E stains and immunohistochemical stains for cytokeratin. Cytokeratin-positive SLN were defined as any SLN with a defined cluster of positive staining cells which could be confirmed histologically on H&E sections. Finally, a review of the worldwide data was undertaken using a uniform analytical method to compare the rates of sensitivity, diagnostic accuracy, and false negatives of SLN mapping. RESULTS: In 167 patients, 337 SLN were harvested, for an average of 2.01 SLN/patient. Fifty-two (31.1%) of the patients had metastasis in the SLN. In the 115 patients with negative SLN, 1 was found to have tumor in higher axillary nodes, for a false negative rate of 0.88%. Fifty-nine (37.8%) of the patients were diagnosed by fine-needle aspiration, 89 (53.3%) by excisional biopsy, and 19 (11.4%) by core biopsy. Positive SLN were identified in 1/17 (5.9%) patients with DCIS. Metastasis was found in 33/115 (28.7%) of the patients with infiltrating ductal tumors and in 11/19 (57.9%) of the patients with infiltrating lobular tumors. Positive SLN were identified in 7/16 (43.7%) of the patients with mixed cellularity tumors. Metastasis in the SLN was detected in 7/55 (12.7%) of the 59 patients with T1a-T1b tumors and in 21/58 (36.2%) of the patients with T1c tumors. Positive SLN were found in 17/30 (56.7%) of the patients with T2 tumors and in 6/7 (85.7%) of the patients with T3 tumors. A literature review of 731 patients (including this study) demonstrates a sensitivity rate of 95% and a diagnostic accuracy rate of 98%. The overall false negative rate is 3.1%. CONCLUSIONS: This study demonstrates that SLN biopsy is a highly sensitive and accurate method of predicting axillary nodal status. It is a reproducible technique that is easily learned. The future addition of more sensitive methods such as PCR evaluation of nodal involvement may reduce the need for widespread use of adjuvant chemotherapy with its high cost and attendant morbidity and mortality. We believe that this technique will eventually become the standard of care in the treatment of breast cancer, particularly for T1 and T2 lesions and perhaps also for high-grade DCIS tumors.

Biliary glycoprotein is overexpressed in human colon cancer cells with high metastatic potential.

Carcinoembryonic antigen (CEA) has been recently implicated in the process of human colon cancer liver metastasis by means of an adhesion mechanism. Based on the strong sequence and structural homology of biliary glycoprotein (BGP) to CEA, we hypothesized that BGP might be overexpressed at the RNA and protein level in tumor cells with high metastatic potential. We have found the BGP messenger RNA derived from highly metastatic colon cancer cells is constitutively overexpressed-nearly fourfold greater than poorly metastatic cells-and that BGP expression is induced by interferon-gamma. Similarly, we have demonstrated that BGP protein levels were constitutively elevated in highly metastatic human colon cancer cells when compared to poorly metastatic cells. Collectively these results suggest that the basal and interferon-stimulated expression of BGP transcripts may be regulated in a manner similar to CEA and that a potential role in the process of metastasis may be inferred.

Role of computed tomographic arterial portography and intraoperative ultrasound in the evaluation of patients for resectability of hepatic lesions.

Computed tomographic arterial portography (CTAP) has been shown to be the most sensitive preoperative test for determining resectability of hepatic lesions but we have shown it to have low specificity. Intraoperative ultrasound (IOUS) evaluation of the liver has also been proposed as an accurate means of assessing resectability. We sought to compare the effectiveness of the two modalities. Fifty-six patients who had been deemed candidates for liver resection based on CTAP findings underwent systematic exploration, liver mobilization, and IOUS examination. Ultrasound findings were compared with results of CTAP. In 46 patients the IOUS findings were in complete agreement with those of CTAP. In 10 patients CTAP lesions could not be verified by IOUS and these patients did not undergo resection. Follow-up of these 10 patients revealed eight who did not have progression of malignancy at the CTAP-predicted site (CTAP false positive). Two patients did have progression at a CTAP-positive IOUS-negative site (IOUS false negative). Sensitivity for CTAP and IOUS was 100% and 96%, respectively. Specificity for IOUS was 100%. These findings demonstrate the high sensitivity of CTAP and the high sensitivity and specificity of IOUS. CTAP may "overcall" hepatic lesions but IOUS can correctly identify these false positives in most instances. Because CTAP is useful for determining which patients might benefit from surgical exploration, we conclude that the two modalities are complementary for the assessment of resectability of hepatic lesions. The false positive rate for CTAP implies that caution must be used when declining to operate on patients on the basis of this test.

NCCN Practice Guidelines for Colorectal Cancer.

The NCCN Colorectal Cancer Guidelines panel believes that a multidisciplinary approach is necessary for the management of the patient with colorectal cancer. The panel endorses the concept that treatment of patients in a clinical trial has priority over standard or accepted therapy. The recommended surgical procedure for resectable colon cancer is an en bloc resection; laparoscopic surgery should be done only in the context of a clinical trial. For patients with stage III disease, 5-FU-based adjuvant therapy is recommended. A patient who has metastatic disease in the liver or lung should be considered for surgical resection if he or she is a candidate for surgery and if surgery can extend survival. Surgery should be followed by adjuvant chemotherapy. The panel advocates a conservative post-treatment surveillance program for colon and rectal carcinoma patients. Serial CEA determinations are appropriate if the patient is a candidate for aggressive surgical resection, should recurrence be detected. Abdominal and pelvic CT scans should be utilized only when there are clinical indications of possible recurrence. Patients whose disease progresses during 5-FU-based therapy should be treated with irinotecan or encouraged to participate in a phase I or phase II clinical trial.