Targeting CD74 in B-cell non-Hodgkin lymphoma with the antibody-drug conjugate STRO-001

Overexpression of CD74, a type II transmembrane glycoprotein involved in MHC class II antigen presentation, has been reported in many B-cell non-Hodgkin lymphomas (NHLs) and in multiple myeloma (MM). STRO-001 is a site-specific, predominantly single-species antibody-drug conjugate (ADC) that targets CD74 and has demonstrated efficacy in xenograft models of MM and tolerability in non-human primates. Here we report results of preclinical studies designed to elucidate the potential role of STRO-001 in B-cell NHL. STRO-001 displayed nanomolar and sub-nanomolar cytotoxicity in 88% (15/17) of cancer cell lines tested. STRO-001 showed potent cytotoxicity on proliferating B cells while limited cytotoxicity was observed on naïve human B cells. A linear dose-response relationship was demonstrated in vivo for DLBCL models SU-DHL-6 and U2932. Tumor regression was induced at doses less than 5 mg/kg, while maximal activity with complete cures were observed starting at 10 mg/kg. In MCL Mino and Jeko-1 xenografts, STRO-001 starting at 3 mg/kg significantly prolonged survival or induced tumor regression, respectively, leading to tumor eradication in both models. In summary, high CD74 expression levels in tumors, nanomolar cellular potency, and significant anti-tumor in DLBCL and MCL xenograft models support the ongoing clinical study of STRO-001 in patients with B-cell NHL.

Egg-Derived Anti-SARS-CoV-2 Immunoglobulin Y (IgY) With Broad Variant Activity as Intranasal Prophylaxis Against COVID-19

COVID-19 emergency use authorizations and approvals for vaccines were achieved in record time. However, there remains a need to develop additional safe, effective, easy-to-produce, and inexpensive prevention to reduce the risk of acquiring SARS-CoV-2 infection. This need is due to difficulties in vaccine manufacturing and distribution, vaccine hesitancy, and, critically, the increased prevalence of SARS-CoV-2 variants with greater contagiousness or reduced sensitivity to immunity. Antibodies from eggs of hens (immunoglobulin Y; IgY) that were administered the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein were developed for use as nasal drops to capture the virus on the nasal mucosa. Although initially raised against the 2019 novel coronavirus index strain (2019-nCoV), these anti-SARS-CoV-2 RBD IgY surprisingly had indistinguishable enzyme-linked immunosorbent assay binding against variants of concern that have emerged, including Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2), and Omicron (B.1.1.529). This is different from sera of immunized or convalescent patients. Culture neutralization titers against available Alpha, Beta, and Delta were also indistinguishable from the index SARS-CoV-2 strain. Efforts to develop these IgY for clinical use demonstrated that the intranasal anti-SARS-CoV-2 RBD IgY preparation showed no binding (cross-reactivity) to a variety of human tissues and had an excellent safety profile in rats following 28-day intranasal delivery of the formulated IgY. A double-blind, randomized, placebo-controlled phase 1 study evaluating single-ascending and multiple doses of anti-SARS-CoV-2 RBD IgY administered intranasally for 14 days in 48 healthy adults also demonstrated an excellent safety and tolerability profile, and no evidence of systemic absorption. As these antiviral IgY have broad selectivity against many variants of concern, are fast to produce, and are a low-cost product, their use as prophylaxis to reduce SARS-CoV-2 viral transmission warrants further evaluation.

Clinical Trial Registration

https://www.clinicaltrials.gov/ct2/show/NCT04567810, identifier NCT04567810.

Abstract NT-090: PRECLINICAL ACTIVITY AND SAFETY OF STRO-002, A NOVEL ADC TARGETING FOLATE RECEPTOR ALPHA FOR OVARIAN AND ENDOMETRIAL CANCER

OBJECTIVES: Folate receptor alpha (FolRα) is a cell-surface glycoprotein, highly expressed in ovarian and endometrial adenocarcinoma, and thus a promising target for cancer therapy using antibody drug conjugates (ADCs). Most ADCs currently in development are generated by random attachment of the cytotoxic payload to the antibody and result in a heterogeneous mixture, comprised of many different forms that are likely to vary in stability and activity, and therefore may be suboptimal therapeutic agents. We have employed an E. coli cell-free expression system (XpressCFTM) and site-specific conjugation technology, to generate STRO-002, a novel homogenous FolRα-targeting ADC. STRO-002 was optimized by selection of the antibody, drug-linker, conjugation site and drug-antibody ratio (DAR) that conferred the best pharmacological properties. We have conducted preclinical studies to evaluate the stability of STRO-002 and characterize the pharmacological properties of the cytotoxic metabolite SC209. In vitro cytotoxicity assays and in vivo efficacy studies were conducted to evaluate the activity of STRO-002 in multiple ovarian cancer cell lines and xenografts. IND enabling toxicology studies were conducted to determine the safety profiles for STRO-002 and its metabolite SC209 in cynomolgous monkeys and rats, respectively.

RESULTS: Based on optimization studies, the anti-FolRα human IgG1 antibody (H01/SP8166) conjugated to a proprietary cleavable drug-linker (SC239) was selected for the lead ADC STRO-002. SC239 contains a tubulin-targeting 3-aminophenyl hemiasterlin warhead, SC209, which has potent cytotoxic activity. Based on most favorable anti-tumor activity, positions 180 and 404 on each heavy chain were selected for conjugation of SC239 to SP8166 to yield an ADC with DAR of ~ 4.

The drug-linkage in STRO-002 is highly stable and the released warhead, SC209, is a very weak substrate for cellular drug-resistance efflux pumps and is cleared rapidly from plasma. STRO-002 has potent but highly specific cytotoxic activity (0.1-3 nM) on multiple FolRα-positive ovarian cancer cell lines in vitro and anti-tumor efficacy in ovarian xenograft models. STRO-002 exhibits dose-dependent tumor growth inhibition in Igrov-1 tumor xenografts at a single dose and complete regression is achieved in Igrov-1 and OVCAR-3 tumors with a single dose at 10 and 5 mg/kg, respectively. In addition, administration of STRO-002 in combination with carboplatin confers added benefit in efficacy in Igrov-1 tumors. Toxicology studies show favorable safety profiles for STRO-002 and SC209. The main toxicity finding in monkeys dosed up to 9 mg/kg consists of reversible hematopoietic/lymphoid tissue toxicity, which is considered antigen-independent and is consistent with the anti-proliferative effects of SC209 observed in single-dose toxicology studies in rats. No evidence of ocular toxicity due to SC209 were observed in either species.

CONCLUSIONS: STRO-002 is a highly specific FolRα targeting ADC with minimal drug moiety release in circulation and the potential for an improved safety and activity profile, and a reduced risk of tumor drug resistance. Our data supports the advancement of STRO-002 to the clinic as a potential treatment of FolRα expressing malignancies such as ovarian cancer.

Citation Format: Cristina Abrahams, Stellanie Krimm, Xiaofan Li, Sihong Zhou, Jeffrey Hanson, Mary Rose Masikat, Krishna Bajjuri, Tyler Heibeck, Dharti Kothari, Abigail Yu, Robert Henningsen, Cuong Tran, Gang Yin, James Zawada, Julie Hang, Maureen Bruhns, Willy Solis, Alexander Steiner, Adam Galan, Toni Kline, Ryan Stafford, Alice Yam, Venita I. De Almeida, Mark Lupher, Jr., Trevor Hallam. PRECLINICAL ACTIVITY AND SAFETY OF STRO-002, A NOVEL ADC TARGETING FOLATE RECEPTOR ALPHA FOR OVARIAN AND ENDOMETRIAL CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-090.

Abstract 67: Characterization and preclinical development of STRO-001, a novel CD74-targeting antibody-drug conjugate (ADC) for the treatment of B-cell malignancies

CD74 is a type II transmembrane glycoprotein involved in the formation and transport of MHC class II protein. CD74 is highly expressed in many B-cell malignancies with limited expression in normal tissues (Stein R. et al., CCR 2007). STRO-001 is a novel CD74-targeting ADC containing an anti-CD74 aglycosylated human IgG1 antibody (SP7219) conjugated to a non-cleavable dibenzocyclooctyne (DBCO)-maytansinoid linker-warhead. SP7219 was discovered from a Fab ribosome display library based on Sutro’s Xpress CFTM technology. Highly efficient site-specific conjugation enabled by our cell-free antibody production and click chemistry results in a well-defined homogeneous ADC drug product with a drug-antibody ratio (DAR) of 2. Conjugation sites were selected based on highest stability both in vitro and in vivo, thereby limiting loss of drug moiety from STRO-001 in circulation. Due to its limited cell permeability, the major catabolite released by STRO-001 has 1000X lower cell killing activity on CD74 positive and negative cells compared to the reference cytotoxic maytansine. In vitro cytotoxicity assays show potent activity of STRO-001 in a diverse panel of B-cell tumor lines including 4 multiple myeloma (MM), 9 germinal center B-cell (GCB) diffuse large B-cell lymphoma (DLBCL), 3 activated B-cell (ABC) DLBCL, and 3 mantle cell lymphoma (MCL) cell lines with IC50 ranging from 0.17-20 nM. CD74 cell surface expression is required for STRO-001 cytotoxic activity but expression level, as measured by antibody-binding capacity, does not correlate with in vitro potency (R2=0.4640). STRO-001 inhibits the formation of visceral tumors (p<0.004) and prevents growth of CD138+ plasma cells in bone marrow (BM) after 4 weekly doses of 3 mg/kg in the ARP-1 disseminated MM xenograft model. STRO-001 dosed at 3 mg/kg weekly x 3 also eradicates malignant BM plasma cells (p<0.0001) and prolongs survival in the MM.1S disseminated model (100% animals alive at >90 days). STRO-001 exhibits dose-dependent tumor growth inhibition in SU-DHL-6 xenografts starting at 2.5 mg/kg weekly x 3 doses. The combination of bendamustine/rituximab (BR) + STRO-001 further improves tumor suppression in SU-DHL-6 xenografts compared to vehicle (p = 0.002) or BR alone (p = 0.02). Preliminary studies with a MCL xenograft model, Jeko-1, demonstrate potent anti-tumor activity compared to vehicle (p<0.0001) starting at a single STRO-001 dose of 3 mg/kg, with ongoing tumor stasis up to 21 days after treatment. STRO-001 reduces normal B-cells in cynomologous monkeys, providing pharmacodynamic evidence of B-cell targeting. Based on these encouraging observations, STRO-001 is advancing to IND-enabling studies for the treatment of CD74-expressing B-cell malignancies.

Citation Format: Cristina Abrahams, Xiaofan Li, Venita DeAlmeida, Millicent Embry, Abigail Yu, Stellanie Krim, Heidi Hoffmann, James Zawada, Maureen Bruhns, Shannon Matheny, Stuart Bussell, Toni Kline, Alice Yam, Ryan Stafford, Trevor Hallam, Mark Lupher, Arturo Molina. Characterization and preclinical development of STRO-001, a novel CD74-targeting antibody-drug conjugate (ADC) for the treatment of B-cell malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 67. doi:10.1158/1538-7445.AM2017-67

Genetic mapping of brain plasticity across development in Williams syndrome: ERP markers of face and language processing

In Williams Syndrome (WS), a known genetic deletion results in atypical brain function with strengths in face and language processing. We examined how genetic influences on brain activity change with development. In three studies, event-related potentials (ERPs) from large samples of children, adolescents, and adults with the full genetic deletion for WS were compared to typically developing controls, and two adults with partial deletions for WS. Studies 1 and 2 identified ERP markers of brain plasticity in WS across development. Study 3 suggested that, in adults with partial deletions for WS, specific genes may be differentially implicated in face and language processing.

Polythiophenes inhibit prion propagation by stabilizing prion protein (PrP) aggregates

Luminescent conjugated polymers (LCPs) interact with ordered protein aggregates and sensitively detect amyloids of many different proteins, suggesting that they may possess antiprion properties. Here, we show that a variety of anionic, cationic, and zwitterionic LCPs reduced the infectivity of prion-containing brain homogenates and of prion-infected cerebellar organotypic cultured slices and decreased the amount of scrapie isoform of PrP(C) (PrP(Sc)) oligomers that could be captured in an avidity assay. Paradoxically, treatment enhanced the resistance of PrP(Sc) to proteolysis, triggered the compaction, and enhanced the resistance to proteolysis of recombinant mouse PrP(23-231) fibers. These results suggest that LCPs act as antiprion agents by transitioning PrP aggregates into structures with reduced frangibility. Moreover, ELISA on cerebellar organotypic cultured slices and in vitro conversion assays with mouse PrP(23-231) indicated that poly(thiophene-3-acetic acid) may additionally interfere with the generation of PrP(Sc) by stabilizing the conformation of PrP(C) or of a transition intermediate. Therefore, LCPs represent a novel class of antiprion agents whose mode of action appears to rely on hyperstabilization, rather than destabilization, of PrP(Sc) deposits.

Biceps muscle trauma at birth with pseudotumour formation: a cause of poor elbow flexion and supination in birth lesions of the brachial plexus

We retrospectively studied the possibility that direct trauma to the biceps muscle might be the cause of poor elbow flexion and supination in 18 consecutive children with birth lesions of the brachial plexus who had delayed or impaired biceps recovery despite neurophysiological evidence of reinnervation. All had good shoulder and hand function at three months of age. Eight recovered a strong biceps after six months, but nine required a pectoralis minor to biceps transfer to augment elbow flexion and supination. One had a delayed but good recovery of the biceps after microsurgical reconstruction of the plexus. All had a clinical 'pseudotumour' in the biceps muscle, which was biopsied during pectoralis minor transfer in two patients and showed rupture and degeneration of muscle fibres with a fibro-fatty infiltrate, suggesting previous muscle trauma. Direct muscle trauma is an uncommon but important cause of delayed or impaired biceps recovery after brachial plexus birth injuries. Surgery to reinnervate the biceps muscle will not work if substantial muscle damage is present when a suitable muscle transfer should be considered.

A split-EPB tendon sling for chronic post-traumatic palmar instability of the thumb metacarpophalangeal joint

Kessler's extensor pollicis brevis (EPB) palmar tendon sling is a simple and reliable reconstruction for symptomatic palmar instability of the thumb metacarpophalangeal (MP) joint. However, we encountered subluxation of the extensor pollicis longus tendon and extension lag at the MP joint when the entire tendon was used. We modified the technique, splitting the tendon to preserve its function as an MP joint extensor. Six thumb MP joints with anteroposterior instability secondary to hyperextension injury were reconstructed using the split-EPB technique. At an average of 22 months postoperatively, all patients had stable and pain-free MP joints. Pinch strength improved an average of 5.6 kg. MP joint flexion was decreased an average of 17.5 degrees and two patients had flexion contractures of 5 degrees and 20 degrees, respectively. Extensor pollicis longus subluxation and MP extension lag did not occur, and there were no recurrences.

The supination deformity and associated deformities of the upper limb in severe birth lesions of the brachial plexus

We reviewed 42 consecutive children with a supination deformity of the forearm complicating severe birth lesions of the brachial plexus.

The overall incidence over the study period was 6.9% (48 of 696). It was absent in those in Narakas group I (27.6) and occurred in 5.7% of group II (13 of 229), 9.6% of group III (11 of 114) and 23.4% of group IV (18 of 77).

Concurrent deformities at the shoulder, elbow, wrist and hand were always present because of muscular imbalance from poor recovery of C5 and C7, inconsistent recovery of C8 and T1 and good recovery of C6. Early surgical correction improved the function of the upper limb and hand, but there was a tendency to recurrence. Pronation osteotomy placed the hand in a functional position, and increased the arc of rotation of the forearm. The supination deformity recurred in 40% (17 of 42) of those treated by pronation osteotomy alone, probably because of remodelling of the growing bone.

Children should be followed up until skeletal maturity, and the parents counselled on the likelihood of multiple operations.

Seasonal variations and trends in weight and arm circumference of non-pregnant rural Senegalese women, 1990–1997

OBJECTIVE

To describe levels, monthly variations and trends in weight and arm circumference of non-pregnant lactating women living in the Sahel, characterized by one short yearly rainy season (July-October).

METHODS

A mixed unbalanced cross-sectional longitudinal observational study conducted at 3, 5, 7 and 10 months postpartum among 3869 women living in the Sine area in central Senegal who had brought their infants into dispensaries for immunization from January 1990 to February 1997, and 1-5 consecutive children per woman (26 106 visits).

RESULTS

Mean weight was 55.7 kg (s.d.: 7.1), but it varied by 2.5-3.9 kg each year, from high means during the dry season (March-May) to low means at the end of the rainy season (September-November). The prevalence of underweight, overweight and obesity (body mass index (BMI)<18.5, 25-29.9 and >30 kg/m(2), respectively) was 7.6% (95% confidence interval: 7.3, 7.9), 6.4% (6.1, 6.7) and 0.4% (0.3, 0.4), but varied strongly by season (P<0.0001 for all). Unlike weight, mean arm increased during the early rains, a peak season of agricultural work (+0.10 cm/month (s.d.: 0.6) from June to August vs -0.35 kg/month (s.d.: 1.1) for weight). BMI and arm circumference were positively associated with age (mean: 20.8 vs 22.2 kg/m(2) and 25.3 vs 27.4 cm, at 20-24 and 40-49 years, respectively, P<0.0001 for both).

CONCLUSIONS

Season was a major determinant of the anthropometric status of rural African women. Negative energy balance reduced body weight from the onset of agricultural labour, while arm circumference increased during early rains, probably due to high physical activity.

Cerebral vasomotor reactivity testing in head injury: the link between pressure and flow

BACKGROUND

It has been suggested that a moving correlation index between mean arterial blood pressure and intracranial pressure, called PRx, can be used to monitor and quantify cerebral vasomotor reactivity in patients with head injury.

OBJECTIVES

To validate this index and study its relation with cerebral blood flow velocity and cerebral autoregulation; and to identify variables associated with impairment or preservation of cerebral vasomotor reactivity.

METHODS

The PRx was validated in a prospective study of 40 head injured patients. A PRx value of less than 0.3 indicates intact cerebral vasomotor reactivity, and a value of more than 0.3, impaired reactivity. Arterial blood pressure, intracranial pressure, mean cerebral perfusion pressure, and cerebral blood flow velocity, measured bilaterally with transcranial Doppler ultrasound, were recorded. Dynamic cerebrovascular autoregulation was measured using a moving correlation coefficient between arterial blood pressure and cerebral blood flow velocity, the Mx, for each cerebral hemisphere. All variables were compared in patients with intact and impaired cerebral vasomotor reactivity.

RESULTS

No correlation between arterial blood pressure or cerebral perfusion pressure and cerebral blood flow velocity was seen in 19 patients with intact cerebral vasomotor reactivity. In contrast, the correlation between these variables was significant in 21 patients with impaired cerebral vasomotor reactivity, whose cerebral autoregulation was reduced. There was no correlation with intracranial pressure, arterial blood pressure, cerebral perfusion pressure, or interhemispheric cerebral autoregulation differences, but the values for these indices were largely within normal limits.

CONCLUSIONS

The PRx is valid for monitoring and quantifying cerebral vasomotor reactivity in patients with head injury. This intracranial pressure based index reflects changes in cerebral blood flow and cerebral autoregulatory capacity, suggesting a close link between blood flow and intracranial pressure in head injured patients. This explains why increases in arterial blood pressure and cerebral perfusion pressure may be useful for reducing intracranial pressure in selected head injured patients (those with intact cerebral vasomotor reactivity).

[Results of active surveillance of acute flaccid paralysis in the Central African Republic and Chad from 1995 to 2000]

The threefold purpose of this report is to describe the epidemiology of acute flaccid paralysis (AFP), to determine the impact of the National Immunization Days (NID), and evaluate the quality of active surveillance in the Central African Republic (CAR) and Chad. The data in this study was obtained from the Enterovirus Division of the Pastear Institute in Bangui (National WHO Inter-country Reference Laboratory for the CAR and Chad and Regional Poliovirus Reference Laboratory in Africa). An increase in the number of AFP cases was observed in the CAR between 1995 and 2000 and in Chad between 1997 and 2000, mainly as a result of enhancement of the surveillance system. The goals set by the WHO in terms of the proportion of AFP cases with 2 specimens collected within 14 days of onset of paralysis and the number of cases with 60-day follow-up have not been reached in either country. The presence of 2 strains of wild poliovirus (types 1 and 3) and several genotypes (West African 13 and West African 7 for type 1 and Central African and Nigeria-P3 for type 3) not only show that Central Africa is still a significant reservoir for poliovirus transmission but also raise serious doubts about the quality of the NID organized over the last 3 years. The priority of the next NID round must be to reach unimmunized children who have been missed by routine immunization coverage.

Characterization of insulin-like growth factor I (IGF-I) receptor mutants for their effects on IGF-I- and interleukin 4-mediated DNA synthesis of 32D cells

Recently we demonstrated that overexpression of the wild type insulin-like growth factor I receptor (IGF-IRWT) in 32D myeloid progenitor cells led to cell proliferation in response to interleukin 4 (IL-4) as well as insulin-like growth factor I (IGF-I) in the absence of insulin receptor substrate expression (Soon, L., Flechner, L., Gutkind, J. S., Wang, L. H., Baserga, R., Pierce, J. H., and Li, W. (1999) Mol. Cell. Biol. 19, 3816-3828). To understand the structural importance of insulin-like growth factor I receptor (IGF-IR) in mediating IL-4- and IGF-I-induced DNA synthesis, we transfected various mutants of IGF-IR to 32D cells. Our results show that most mutants, including Y1250F, Y1251F, Y1250F/Y1251F, S1280A/S1281A/S1282A/S1283A, Y1316F, and 1245d, still retained mitogenic response toward IGF-I or IL-4. However, the Y950F, Y1131F, and Y1135F mutants were not able to respond to either ligand. The H1293F/K1294R and 1293d mutants reduced response toward IGF-I but not to IL-4. Phosphorylation of Shc was greatly reduced in those three mutants that lost mitogenic response. The MAPK activity was much lower in Y1131F and Y1135F mutants, indicating the importance of the Shc/MAPK pathway in IGF-I-induced mitogenesis. Importantly, the synergistic effect of these two factors on DNA synthesis was not affected in cells expressing most of the mutants, even in those three that had lower mitogenic response toward a single ligand. These results suggest that an unidentified pathway(s) may be induced upon co-addition of IGF-I and IL-4 that sustains the intact mitogenesis.

Risk factors related to operative mortality and morbidity in patients undergoing emergency gastrectomy

BACKGROUND

Emergency gastric resection for complicated peptic ulcer and gastric cancer is a major challenge for general surgeons. This study aimed to evaluate the results of emergency gastrectomy and to examine the factors that predict the operative outcome.

METHODS

A total of 82 consecutive patients who underwent emergency gastrectomy were studied. The following variables were assessed: pathology, mortality rate, morbidity, reasons for reoperation and factors related to the outcome.

RESULTS

There were 64 men and 18 women with a median age of 62 (range 30-90) years. The indications were bleeding and perforated gastric or duodenal ulcers in 45 and 20 patients respectively, and bleeding and perforated gastric tumours in seven and ten patients respectively. The overall mortality rate was 17 per cent (n = 14). The complication rate was 63 per cent and 11 patients (13 per cent) required reoperation. By multivariate analysis, age greater than 65 years and blood haemoglobin level less than 10 g/dl on admission were predictive of complications after emergency gastrectomy. Postoperative pulmonary and cardiac complications and hypotension on admission were independent risk factors associated with operative death.

CONCLUSION

Age more than 65 years, haemoglobin level less than 10 g/dl and hypotension on admission were associated with a poor outcome after emergency gastrectomy. The operative result was not affected by the underlying gastric pathology.

Loss of PTEN expression leading to high Akt activation in human multiple myelomas

Mouse plasma cell tumor (PCT) and human multiple myeloma (MM) are terminal B-cell malignancies sharing many similarities. Our recent work demonstrated that activation of the insulin-like growth factor receptor (IGF-IR)/insulin receptor substrate (IRS)/phosphatidylinositol 3' kinase (PI 3'K) pathway was evident in the tumor lines derived from both species. Although PI 3'K activity was higher in mouse tumor lines than that in human tumors, activation of Akt serine/threonine kinase was markedly lower in mouse lines. This discrepancy prompted us to test the status of PTEN tumor suppressor gene, as it has been shown to be a negative regulator of PI 3'K activity. Although all the mouse lines expressed intact PTEN, 2 of the 4 human lines (Delta47 and OPM2) possessing the highest Akt activity lost PTEN expression. Sequencing analysis demonstrated that the PTEN gene contains a deletion spacing from exon 3 to exon 5 or 6 in the Delta47 line and from exon 3 to 7 in the OPM2 line. Restoration of PTEN expression suppressed IGF-I-induced Akt activity, suggesting that loss of PTEN is responsible for uncontrolled Akt activity in these 2 lines. Despite the expression of PTEN with the concomitant low Akt activity in all mouse PCT lines, their p70S6K activities were generally higher than those in 3 human MM lines, arguing for specific negative regulation of Akt, but not p70S6K by PTEN. These results suggest that p70S6K and Akt may be differentially used by the plasma cell tumors derived from mice and humans, respectively.

Activation of insulin-like growth factor I receptor signaling pathway is critical for mouse plasma cell tumor growth

Plasma cell neoplasia in humans generally occurs as multiple myeloma, an incurable form of cancer. Tumors with marked similarity can be induced in mice by a variety of agents, including chemicals, silicone, and oncogene-containing retroviruses, suggesting the use of murine tumors as an informative model to study plasma cell disease. Herein, we have focused on the role of insulin-like growth factor I receptor (IGF-IR) signaling in the development of plasma cell disease. The insulin receptor substrate 2/phosphatidylinositol 3'-kinase/p70S6K pathway was found to be either constitutively or IGF-I-dependently activated in all plasma cell tumors. Biological relevance was demonstrated in that plasma cell lines with up-regulated IGF-IR expression levels exhibited mitogenic responses to IGF-I. More importantly, expression of a dominant-negative mutant of IGF-IR in these lines strongly suppressed tumorigenesis in vivo. Taken together, these results demonstrate that up-regulation and activation of IGF-IR and the downstream signaling pathway involving insulin receptor substrate 2, phosphatidylinositol 3'-kinase, and p70S6K may play an important role in the development of a broad spectrum of plasma cell tumors.

Protein kinase C-alpha overexpression stimulates Akt activity and suppresses apoptosis induced by interleukin 3 withdrawal

To investigate the role of protein kinase C (PKC) in apoptotic signaling induced by cytokine withdrawal, we expressed PKC-alpha, -delta and -epsilon individually in the 32D myeloid progenitor cells. The parental and PKC-delta- and PKC-epsilon-transfected 32D cells underwent apoptosis within 24 h in the absence of interleukin 3. In contrast, expression of PKC-alpha inhibited the onset of apoptosis as determined by genomic DNA fragmentation and flow cytometric analysis. Correlating with the inhibition of apoptosis, PKC-alpha transfectants exhibited increased activity of the endogenous Akt serine/threonine kinase. Furthermore, PKC-alpha, but not PKC-delta or -epsilon, specifically activated overexpressed Akt. PKC-alpha-induced Akt activity was partially dependent on phosphoinositol 3' kinase (PI 3'K) since a PI 3'K inhibitor was able to suppress PKC-alpha-induced Akt activation. Both basal and interleukin 3-stimulated phosphorylation of Akt on serine 473 was enhanced in the PKC-alpha and Akt contransfectants. Coexpression of wild type Akt and PKC-alpha resulted in greater suppression of apoptosis than PKC-alpha expression alone. Together, our results demonstrate that suppression of apoptosis by PKC-alpha correlates with its ability of activating endogenous Akt. Furthermore, activation of overexpressed Akt by PKC-alpha is consistent with their synergistic effect on suppressing apoptosis, providing the strong evidence of cross talk between Akt and PKC-alpha.

Entry and integration of transplanted hepatocytes in rat liver plates occur by disruption of hepatic sinusoidal endothelium

To establish the process by which transplanted cells integrate into the liver parenchyma, we used dipeptidyl peptidase IV-deficient F344 rats as hosts. On intrasplenic injection, transplanted hepatocytes immediately entered liver sinusoids, along with attenuation of portal vein radicles on angiography. However, a large fraction of transplanted cells (>70%) was rapidly cleared from portal spaces by phagocyte/macrophage responses. On the other hand, transplanted hepatocytes entering the hepatic sinusoids showed superior survival. These cells translocated from sinusoids into liver plates between 16 and 20 hours after transplantation, during which electron microscopy showed disruption of the sinusoidal endothelium. Interestingly, production of vascular endothelial growth factor was observed in hepatocytes before endothelial disruptions. Portal hypertension and angiographic changes resulting from cell transplantation resolved promptly. Integration of transplanted hepatocytes in the liver parenchyma required cell membrane regenesis, with hybrid gap junctions and bile canaliculi forming over 3 to 7 days after cell transplantation. We propose that strategies to deposit cells into distal hepatic sinusoids, to disrupt sinusoidal endothelium for facilitating cell entry into liver plates, and to accelerate cell integrations into liver parenchyma will advance applications of hepatocyte transplantation.

Randomised study of the possible adjuvant effect of BCG vaccine on the immunogenicity of diphtheria-tetanus-acellular pertussis vaccine in Senegalese infants

Following a study in Senegal (1990-1995) in which the relative efficacy of a diphtheria-tetanus-acellular pertussis vaccine (DTaP) was compared with that of a diphtheria-tetanus-whole-cell pertussis vaccine in children given a simultaneous injection of Bacille Calmette-Guérin (BCG) vaccine, this subsequent study was conducted to evaluate the possible adjuvant effect of the BCG vaccine on acellular pertussis vaccine components. A second objective was to compare the immunogenicity of these components when administered in accordance with a 2-4-6-month (spaced) schedule or an accelerated 2-3-4-month schedule. In all, 390 healthy Senegalese infants were randomly divided into three groups of 130 infants. Antibodies to acellular pertussis components were measured in serum samples obtained within 2 days of the first DTaP dose and 1 month after the third dose. BCG vaccine, given simultaneously with the DTaP vaccine, did not influence the immunogenicity of the acellular pertussis vaccine components when compared with separate administration of the two vaccines. Infants immunised according to a 2-4-6-month schedule had a significantly higher immune response than those immunised according to a 2-3-4-month schedule with respect to the response to pertussis toxoid assessed by seroneutralisation on Chinese hamster ovary cells (P<0.0001). These results suggest that BCG and DTaP vaccines can be given simultaneously without interference or enhancement and that more optimal immunogenicity is achieved with an extended than with an accelerated schedule.

Stem cells and rat liver carcinogenesis: contributions of confocal and electron microscopy

Microscopic analysis in combination with cytochemistry and immunocytochemistry has revealed the presence of four cell types not previously described in the portal area and parenchyma of the liver from an experimental rodent hepatocarcinogenic rat model. Within the intrahepatic bile ductules, which proliferate after administration of chemical carcinogens and partial hepatectomy, small, undifferentiated nonpolarized, nonepithelial cells with a blast-like phenotype and polarized epithelial cells different from the polarized epithelial cells that typically line the walls of the bile ductules were found. In the connective tissue stroma surrounding the bile ductules, nonpolarized epithelial cells with hepatocyte phenotype were found. In the parenchyma, subpopulations of bile ductule epithelial cells that established ATPase-positive bile canalicular structures, including the formation of desmosomes and tight junctions, with parenchymal hepatocytes within the hepatic lobule were found. These observations raise the following questions in this model. Are there undifferentiated progenitor cells with stem cell-like properties within bile ductules? What are the interrelations of the newly described cell types with each other, with parenchymal hepatocytes, with preneoplastic nodules, and with hepatomas? Do the heterogeneous cell types within the bile ductules, in the surrounding connective tissue, and within the hepatic cords represent intermediate stages of single or multiple cell lineage pathways leading to hepatocyte differentiation, liver regeneration, and/or preneoplastic nodule formation?

Evaluation of an immunoglobulin G enzyme-linked immunosorbent assay for pertussis toxin and filamentous hemagglutinin in diagnosis of pertussis in Senegal

The enzyme-linked immunosorbent assay is widely employed for the serological diagnosis of pertussis. It is generally concluded that a significant increase in specific immunoglobulin G (IgG) or IgA against the pertussis toxin (PT) or against filamentous hemagglutinin (FHA) in paired sera correlates with Bordetella pertussis infection. However, this type of diagnosis of pertussis has mainly been applied to unvaccinated children, with timely sampling of acute- and convalescent-phase sera. In current practice and in epidemiological studies, such criteria are not always fulfilled. The aim of this study was to analyze the significance of decreases in IgG antibody titers against PT and FHA between paired sera observed in suspected cases of pertussis infection. Serological results from paired sera were available for 460 children experiencing at least 8 days of cough. An anti-PT IgG decrease was observed in 25% of the children, more frequently than the anti-FHA IgG decrease. Fourteen percent of the serologic decreases were observed in children with culture-confirmed infection, and 59% of the decreases were observed in children with confirmation criteria according to World Health Organization recommendations. Most of the decreases were observed when serum samples were collected according to a standard recommended schedule. Serologic decreases were observed more frequently among vaccinated children than among unvaccinated children. This difference, which was highly significant (P < 0.00001), was explained by the different kinetics of the antibody responses between vaccinated and unvaccinated children. The importance of the antibody response for the evaluation of vaccine efficacy, namely a bias toward higher absolute vaccine efficacy when this response is not taken into account, is discussed. This study supports an earlier recommendation that a significant decrease in PT or FHA should be added to the diagnostic criteria for pertussis.

A randomized double-blind trial comparing a two-component acellular to a whole-cell pertussis vaccine in Senegal

A randomized, double-blind trial comparing a diphtheria-tetanus-acellular pertussis vaccine (DTaP) (pertussis toxoid and filamentous hemagglutinin) with a whole-cell vaccine (DTwP) was conducted. A case-contact study was nested in the trial to estimate absolute efficacy. From 1990 through 1994, 4181 children were randomized to receive one of the vaccines at 2, 4, and 6 months. Severe adverse events were monitored weekly during two visits after vaccination. Fewer serious adverse events were observed after DTaP. Surveillance for cough illnesses persisting more than 7 days, in children under 15 years of age, was made by weekly home visits. Examining physicians, blind to vaccination status, took samples for culture and serologic testing. Pertussis was defined as 21 or more days of cough confirmed by culture, serology, or contact with a culture-confirmed person. Beginning 28 days after the third vaccine dose, the overall ratio of pertussis incidence in the DTaP group relative to the DTwP group (RRac/wc) was 1.54 (95% CI, 1.23-1.93). In children younger than 18 months of age, RRac/wc was 1.16 (95% CI, 0.77-1.73) and 1.76 (95% CI, 1.33-2.33) in children older than 18 months, which suggests a shorter duration of protection with the acellular vaccine (P = 0.090). Absolute efficacy estimates derived from the case-contact study confirmed the lower protection afforded by the acellular vaccine compared with the whole-cell vaccine: 31% (95% CI, 7-49) versus 55% against the protocol case definition, and 85% (95% CI, 66-93) versus 96% for the more severe WHO case definition. Although vaccination with DTaP provided a lower degree of protection than the highly effective DTwP, this difference was less prominent before 18 months of age, the customary age for a fourth dose. The safer DTaP vaccine may prove a valuable substitute for whole-cell vaccines when used in a schedule that includes a booster-dose.

Comparative safety and immunogenicity of an acellular versus whole-cell pertussis component of diphtheria-tetanus-pertussis vaccines in Senegalese infants

A diphtheria and tetanus toxoid two-component acellular pertussis vaccine (DTaP), consisting of 25 micrograms glutaraldehyde-detoxified pertussis toxin (PT) and 25 micrograms native filamentous hemagglutinin (FHA), was compared with diphtheria and tetanus toxoid whole-cell pertussis vaccine (DTwP) in a randomized, double-blind manner in 286 Senegalese infants inoculated at two, four, and six months of age. In infants receiving DTaP a significantly lower rate of local reactions, crying and fever was observed than in infants receiving DTwP. One month after the third dose, the geometric mean titres for FHA antibodies were higher in the DTaP group, whereas increases in PT antibody titres were higher in the DTwP group. More than 90% of the infants had a fourfold or more increase in antibodies to both PT and FHA with either vaccine. Diphtheria, tetanus, and polio antibody responses were also measured and found to be comparable between the two groups. The results of this pilot study support the implementation of a field trial to compare the protective efficacy of these vaccines against pertussis in the same setting.

Blast-like cell compartment in carcinogen-induced proliferating bile ductules

Small non-epithelial cells with morphological features of blast-like cells are found within a proliferating intrahepatic biliary system after institution in rats of a diethylnitrosamine, 2-acetylaminofluorene, partial hepatectomy carcinogenesis protocol. Two to three days after the partial hepatectomy step of the carcinogen protocol, the small blast-like cells are evident beneath a layer of bile ductule epithelial cells that line the walls of the bile ductules. The basally located small cells are not exposed to the bile ductule lumen or to the surrounding basal lamina. They ranged in size from 3.0 to 5.0 microns, exhibit an undifferentiated phenotype, including a high nucleus-to-cytoplasm ratio and no to minimal differentiated cytoplasmic and surface structures. Mitosis of blast-like cells are evident, and their nuclei express proliferating nuclear cell antigen. The ductal blast-like cells do not express cytokeratin 19, oval cell antigen 270.38, or actin immunoreactivity, in contrast to bile ductule epithelial cells. The basal cells, as well as bile ductule epithelial cells, are negative for a panel of T and B lymphocyte surface markers in contrast to lymphocytes present in the connective tissue stroma surrounding the bile ductules and throughout the hepatic parenchyma. Within some segments of the biliary system, some of the ductal blast-like cells increased in size to approximately 10 microns and showed increased amounts of cytoplasmic organelles and plasma membrane filapodia but did not develop the polarized phenotype of bile ductule epithelial cells (ie, apical microvilli, desmosomes, connections to bile ductule cells, and exposure to duct lumen); however, their nuclear morphology was essentially similar to the smaller basal cells. We also found bile ductules to contain two types of polarized epithelial cells, one with the characteristic oval nucleus of the oval/bile ductule epithelial cells and the other, transitional epithelial cells with a rounder nucleus and prominent nucleoli. The transitional cells exhibit a similar apical-basal polarity and antigenic phenotype as the oval/bile ductule epithelial cells. However, transitional cells are larger and have an overall less dense cytoplasm than the bile ductule epithelial/oval cells, and some show apical microvilli changes and small catalase-positive peroxisomes. These observations indicate that a greater diversity of cell types exist within intrahepatic bile ductules of rats treated with carcinogens. Furthermore, the nonpolarized ductal blast-like cells undergo proliferation and are significantly different in phenotype from other hepatic cells previously reported as candidates for liver progenitor cells.

Characterizations of and interactions between bile ductule cells and hepatocytes in early stages of rat hepatocarcinogenesis induced by ethionine

Numerous hepatic cell lineage pathways have been proposed for the development of hepatocarcinogensis induced by chemical carcinogens in rats. The roles of bile ductule cells and hepatocytes in the development of carcinogenesis were investigated using light and electron microscopic procedures to detect differences in morphology and in the phenotypic expression of antigens that are associated with each cell type. In early stages of hepatocarcinogenesis (4-10 weeks after initiation of feeding of a choline-deficient ethionine containing diet), both bile ductulelike (BDL) cells and hepatocytes were seen in mitosis. At the light microscope level, BDL cells showed intense cytoplasmic pyronin (RNA) staining and were positive for the antigens defined by monoclonal antibody 270.38 (bile ductule cells and "oval" cell marker) and glutathione-S-transferase (Yp isoform), whereas hepatocytes were positive for the antigens defined by monoclonal antibodies 270.26 and 258.26 (liver parenchymal cell markers), catalase activity (peroxisome marker) and adenosine triphospatase activity (bile canalicular marker). The authors frequently encountered BDL cells and hepatocytes in close proximity. Ultrastructural examination showed extensive plasma membrane appositions between a subset of BDL cells and hepatocytes. Desmosome structures, tight junctions, microvilli interdigitations and ATPase-positive bile canalicularlike structures were present along the contiguous plasma membrane domains of BDL cells and hepatocytes. Many of the BDL cells attached to hepatocytes were also attached to other BDL cells that had retained a basal lamina. In many cases, BDL cells connected to both hepatocytes and other BDL cells were no longer completely surrounded by basal lamina and had acquired a dual polarity as a consequence of their sharing apical and lateral membrane domains with both BDL cells and hepatocytes. BDL cells showed increased numbers of microperoxisomes (catalase positive organelles) and numerous free ribosomes. Hepatocytes showed a prominent development of the smooth endoplasmic reticulum, a feature prominent in hepatocytes within hyperplastic nodules. Since BDL cells and hepatocytes proliferate and BDL cells and hepatocytes develop intercellular junction sites, the authors propose that both cell types in early stages of carcinogenesis have the capacity to enter the cell lineage pathway leading to the development of hepatocarcinoma. Furthermore, the finding that BDL cells and hepatocytes form multiple attachment sites at the level of the plasma membrane, suggests the possibility that at some stage convergence of separate hepatic cell pathways may occur.

Factor VIII-related antigen levels in normal pregnancy and puerperium

The changes in serum Factor VIII-related antigen (Factor VIII RAg) levels in normal pregnancy and puerperium in Chinese women were studied by the Laurell 'rocket' immunoelectrophoresis. At 6 wk of gestation, the serum Factor VIII RAg levels were already higher than those of non-pregnant women and gradually increased through term pregnancy. Parturition did not have immediate effects on the circulating levels of Factor VIII RAg. The levels of Factor VIII RAg observed during labour and days 1-5 postpartum were similar to those of term pregnancy. By the 6th wk postpartum, the serum Factor VIII RAg declined to basal levels, similar to those of non-pregnant control samples.

Immunocytochemical localization of lysosomal beta-galactosidase in rat liver

beta-galactosidase is a ubiquitous lysosomal hydrolase that specifically cleaves terminal beta-galactosyl residues from glycoproteins, glycosaminoglycans, oligosaccharides, and glycolipids. To study the intracellular distribution of this enzyme, we prepared a specific polyclonal antibody to lysosomal beta-galactosidase by immunizing rabbits with a highly purified preparation of beta-galactosidase from rat liver. Using this antibody we employed an immunocytochemical technique (protein A coupled to horseradish peroxidase and diaminobenzidine cytochemistry) and showed that beta-galactosidase is present in all hepatocytes of the rat liver. All types of lysosomes, the rough endoplasmic reticulum, and the specialized region of smooth endoplasmic reticulum known as GERL showed immunoreactivity. This in situ distribution suggests that these organelles are involved in the biosynthesis and intracellular sorting of this lysosomal enzyme.

Immunocytochemical localization of alpha-D-mannosidase II in the Golgi apparatus of rat liver

Mannosidase II is involved in the trimming of alpha-1,6-mannosyl residues during the biosynthesis of glycoproteins containing N-linked oligosaccharides of the complex type. A highly specific polyclonal antibody (IgG) was isolated from rabbits immunized with a homogeneous preparation of mannosidase II prepared from rat liver. With this antibody, light and electron microscopic immunocytochemical studies on rat liver reveal that essentially all mannosidase II in hepatocytes is localized in the Golgi apparatus, the only other site with reaction product being the endoplasmic reticulum. The indirect immunocytochemical method used in this study involved three major steps: exposure of aldehyde-fixed tissue to immune and nonimmune IgG, treatment with staphylococcal protein A labeled with horseradish peroxidase, and incubation in diaminobenzidine to reveal sites of peroxidase activity. The procedures described overcome major problems in immunocytochemistry, allowing preservation of antigenic sites and maintaining adequate ultrastructural integrity. The in situ localization of other carbohydrate-processing enzymes, involved in either trimming or attachment of sugar residues, should be possible with this procedure. Because biosynthetic precursors of the processing enzymes may be revealed by an immunocytochemical approach, it is potentially significant that mannosidase II reaction product is present in areas of the endoplasmic reticulum as well as in the Golgi apparatus.

Lysosomal compartment of macrophages: extending the definition of GERL

"Professional phagocytes" such as Kupffer cells show an extensive network of interconnected residual bodies with cytochemically demonstrable acid phosphatase [orthophosphoric monoester phosphohydrolase (acid optimum), EC 3.1.3.2]. In such cells and in other (hepatocytes, etc.) this compartment may be considered a part of GERL [a hydrolase-rich region of endoplasmic reticulum (ER) situated at the trans face of the Golgi apparatus from which various Lysosomes appear to arise].

Biochemical and morphologic studies on diabetic rats: effects of sucrose-enriched diet in rats with pancreatic islet transplants

Isolated pancreatic islets were administered to Lewis rats with streptozotocin-induced diabetes. Then the rats were fed either a semisynthetic diet containing 60% (wt/wt) sucrose for 3 weeks or were continued on chow. Transplantation resulted in a decrease in serum glucose, an increase in serum insulin, and a marked decrease in serum triacylglycerol, particularly in the sucrose-fed diabetic rats. In these rats, in demarcated areas of hepatocytes surrounding portal vein termini, lipid was deposited in the cytosol and large lipoprotein particles engorged the Golgi apparatus, Golgi-derived secretory vacuoles, and GERL. This model permits observation of the effects of pancreatic islet hormones on lipogenesis by hepatocytes in situ.

Immunocytochemical localization of epoxide hydrase in hyperplastic nodules induced in rat liver by 2-acetylaminofluorene

A knowledge of the biological characteristics of carcinogen-induced hyperplastic nodules of rat liver may be important in the understanding of cancer development. Although its biological role remains to be elucidated, the level of microsomal epoxide hydrase (epoxide hydrolase, EC 3.3.2.3) is 5- to 7-fold greater in hyperplastic nodules nodules induced by feeding the hepatocarcinogen 2-acetylaminofluorene than in liver of control rats. After removal of the carcinogen from the diet, the high level of the enzyme is maintained in those nodules that persist and in the hepatocellular carcinomas that subsequently develop. The availability of antibody to the epoxide hydrase made it possible to use electron microscopic immunocytochemistry to localize this enzyme in the cells of hyperplastic nodules. The immunocytochemical procedure provides direct visual evidence for the presence of this enzyme in smooth endoplasmic reticulum and also in rough endoplasmic reticulum (including the nuclear envelope) of the nodule's parenchymal cells.

Sites of lipoprotein particles in normal rat hepatocytes

Very low density lipoprotein (VLDL) particles are packaged by the Golgi apparatus into vacuoles which move to the plasma membrane and empty the particles into the space of Disse, via exocytosis. Traditionally, all lipoprotein-containing cisternae and vacuoles are thought to be parts of this pathway. Observations reported here demonstrate that there is a second population of lipoprotein-containing cisternae and vacuoles. This population is part of GERL, an organelle we consider to be a specialized hydrolase-rich region of the endoplasmic reticulum (ER). To our knowledge, this is the first systematic study of GERL in normal rat hepatocytes.

The cytochemical demonstration of GERL in rat hepatocytes during lipoprotein mobilization

When a semisynthetic diet containing 1% orotic acid (OA) is fed to rats, the endoplasmic reticulum (ER) of hepatocytes vesiculates and lipoprotein (LP) droplets accumulate within the vesicles. When clofibrate (ethyl chlorophenoxyisobutyrate, CPIB) is added to the orotic acid-rich diet, the ER cisternae reform and the LP is mobilized through the reconstituted ER. A remarkable restoration of normal hepatocyte ultrastructure occurs except for a few organelles. From their morphological appearance it was suggested that cisternae which became dilated with small LP particles were part of GERL, abnormally enlarged. The present communication validates this interpretation through ultrastructural cytochemistry which can distinguish GERL from the adjacent Colgi apparatus. GERL shows acid phosphatase (AcPase) but not thiamine pyrophosphatase (TPPase) activity. In contrast, the adjacent Golgi element shows thiamine pyrophosphatase but not acid phosphatase activity. From such cytochemical studies we have recently proposed that GERL in normal rat hepatocytes may be involved in transforming LP particles, by enzymes like lipases that were presumed to be present in this hydrolase-rich portion of smooth ER. In the situation studied in this communication, the addition of ethyl chlorophenoxyisobutyrate to the diet causes the release from the ER of large amounts of LP to the Golgi apparatus and to GERL. Apparently the capacity of GERL to metabolize LP is exceeded and lipid accumulates in the residual bodies.

Studies of the secretory process in the mammalian exocrine pancreas. I. The condensing vacuoles

Phosphatase cytochemistry was used to distinguish between the Golgi apparatus and GERL (considered as a specialized region of endoplasmic reticulum [ER] at the inner [trans] aspect of the Golgi stack) in pancreatic exocrine cells of guinea pig, rat, rabbit, and hamster. The trans element of the Golgi stack exhibits thiamine pyrophosphatase (TPPase) but no acid phosphatase (AcPase) activity. In contrast, GERL shows AcPase but no TPPase activity. The nascent secretory granules, or condensing vacuoles, are expanded cisternal portions of GERL. Continuities of condensing vacuoles with rough ER are suggested, and it is proposed that some secretory components may have direct access to the condensing vacuoles from ER. Connections of Golgi apparatus with GERL were not seen.

Cytochemical study of secretory process in transplantable insulinoma of syrian golden hamster

Electron microscopy, including phosphatase cytochemistry, indicates that the secretory granules of an insulinoma producing proinsulin and insulin are packaged by the endoplasmic reticulum (ER) and especially by a specialized region of ER which we call GERL because of the spatial relationship of this region to the Golgi apparatus and its apparent role in producing lysosomes. The granules are not derived from the Golgi apparatus. Preliminary evidence suggests this may be true also of pancreatic beta-cells.